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MG Midget and Sprite Technical - OIL.? Result of mixing different monograde oils.

As per title. Possibly a silly question.

What is the result of mixing two different single viscosity oils?

Example.

1 litre of ep90 gear oil, mixed with 1 litre of ep140 gear oil.

Would the result be ep115?



anamnesis

That's how I always assumed it worked! But I have no evidence to back myself up.
Malcolm

close-----112 using the calculator

https://www.widman.biz/English/Calculators/Mixtures.html
William Revit

Ah.... yes! All things viscosity tend to work on logarithmic scaling so it won't be quite the average, but it will be close enough for quick maths.

Also, to be really dull and geeky... that calculator is in cSt (metric) and, IIRC, oils are based on SAE ratings/viscosities which being American has some sort of random imperial unit that I forget. So a 90 weight oil is 90 somethings viscosity, not cSt... But the maths probably still works the same! :-)

Everyday's a school day here :-D

Malc.
Malcolm

Ah ok, thanks chaps.

Not so silly then.

Here's the reason I asked. In my diff thread ep 140 was suggested by the diff rebuilder

I tried it yesterday, and again very early this morning when it was pretty cold outside. The thicker 140 in my axle is actually noticable when it's cold. It felt like I'd partially left my handbrake on. I could feel the drag/deceleration when coasting slowly, curca below 20mph.

So I wondered, what if, to get the benefit of a thicker oil when hot, and not have it so thick it dragged when cold, I mixed 90 and 140?

I wondered what that middle viscosity would feel like, and if any benefit would follow. But only because I can't find a gl4 85/140.

But anyway, great. A simple answer to a question. 😁 Except that it hadn't occured to me that temperature would have to be considered too. Thanks Willy.

anamnesis

Are you using a straight 140? or a something-w-140?

To get the best of both worlds you want something with a low w rating, then the 140. Like a 75w-140 or an 80w140.

https://www.opieoils.co.uk/c-674-75w-140-gear-oil.aspx

Malc.
Malcolm

Oh, sorry, read things correctly! You say you were struggling to find something that was GL4? I assume for the yellow metals thing?

https://www.opieoils.co.uk/p-69294-millers-oils-classic-differential-oil-85w-140-gl5.aspx

This is claimed to be "non aggressive to yellow metals".

Cheers,
Malc.
Malcolm

EP monograde gear oil. I'm likely sticking to EP90

It was really just an aside related to my diff thread, which I'll update later.

"Non aggressive to yellow metals".

Yep, in that it's phosphor buffered as they say, so non corrosive to the yellows.

But the ep bonding strength of gl5 is 50% greater than gl4, so physically removes particles from yellow metals, because they are weaker than steel.

It might be ok, but if not, goodbye planet gear thrust and cup washers.
anamnesis

Yep yep, I follow. I am keeping up - just :-)

Stick the standard 80w-90 or EP90 in and be done with it. It's what MG recommended and surely those that designed it would know best?

Hope you get sorted and back on the road soon.

Malc.
Malcolm

😁😁.

I love it when two threads start talking about the same thing. 😅😅.

I should have asked my oil mix question in my diff thread. 😉

Might as well move there now and update it. 😁
anamnesis

With all this oil talk it made me think..

Anyone heard from Nigel recently?
timmyk

Yep, he's good
William Revit

now, on oils
I wouldn't be running a straight 140 mineral oil, specially if you're going to do some highway driving. You run the chance of cavitation between the gears
A straight 140 synthetic you might get away with because of it's superior lube quality , a multigrade synthetic is the go
The way I understand the gl4/gl5 thing An. is that yes the gl5 has a stronger bonding strength, that's why it's a higher rated oil and that's why it's supposedly not so suitable for manual gearboxes because it inhibits the friction of the syncro ring which is what syncro rings need to work----it's the gl4 oil with it's lesser bonding that keeps the rubbing surface of the syncro clean by not leaving friction inhibiting deposits on the surface as opposed to a gl5 which does

That's how I understand it but happy to be corrected/learn
William Revit

I'd be going the Motul 75/140 that Malc found----It says in black and white that it's ok for yellow metals

https://www.opieoils.co.uk/p-900-motul-gear-competition-75w-140-fully-synthetic-racing-transmission-ls-differential-oil.aspx
William Revit

Ah but --- 😉,

Trouble is, there's confusion in the statements made by some oil advertising.

GL (gear lubricant) is an EP rating system. I've read a number of texts by oil companies about gl4 and gl5.

This is an extract from a paper written by an oil consultant/engineer named Richard Widman. I've added the full pdf too.

"The Difference between GL-4 and GL-5 Gear Oils by Richard Widman Revision 1-2016"

"The original target audience for this paper was my group of friends in the Corvair world, but it applies to all cars and is particularly important for all classic cars."

"In normal operation, the sulfur/phosphorous additive forms a black sacrificial coating on the gears and anything it touches with a little pressure and temperature. As the gears turn, instead of wearing, the sacrificial coating of additives is pealed off or worn off. This is normal and acceptable in all steel gears. But when one or more of the surfaces is brass or another soft metal, the sacrificial coating is stronger than the base metal, and instead of just peeling off, it takes with it a few microns of brass that it is bound to.

A traditional GL-4 gear oil of any given viscosity has about ½ of the level of sulfur/phosphorous additive that would be in the GL-5 product, so the bond is not as strong, and therefore can be peeled off without peeling a layer of brass (or less brass). This means that the GL-4 product provides a little less extreme pressure protection, so in the differential of a high-powered car, it would not be the ideal product in the differential. To understand this need we should be aware of the fact that the differential is where the final torque is applied to the wheels (in most applications). But in the transmission, we should consider two factors: Do to the fact that the differential applies the final torque, normally we do not need the full EP protection in the transmission where less torque (about 30%) is applied. We need to be able to break the EP protection to stop the spinning of the gears long enough to mesh them or synchronize them. When we use a GL-5 product in a transmission that requires GL-4, we normally find 2 to 4 times as much copper in the used oil as we would with a GL-4 product (with used oil analysis). Eventually the synchronizers wear to the point that they no longer make contact with the other half of the cone, bottoming out before stopping the opposing gear."

"Here is a synchronizer that has been worn by GL-5 oil. You will note that there are no longer any teeth on the brass, completely worn or “peeled” away -" --- See picture.

He also says--

"Just remember that GL-4 and GL-5 are gear oil ratings, not transmission oil ratings. Transmissions have gears and synchronizers. These seemingly conflicting requirements must be met differently.

****** When someone tells you that their GL-5 covers GL-4, remember they are correct as far as EP protection, but that is only half the answer. When they say their Sulfur/Phosphorous additive will not corrode the yellow metals, they are also correct, but if there are enough to meet GL-5 protection, they will slowly peel away your brass synchronizers. "****

So, "Safe for yellow metals" ?

Here is the full paper.

Willy, if you have a mind to, email him.

I did, to ask about the best oil for the Ford Type9 gearbox. He replied in detail. Nice bloke.

Actually, I think I'll email him again, about gl5 in a diff with brass/bronze/copper flat and cup washers.



anamnesis

Forgot to emphasise this bit.

Then read my previous post.

"There is a lot of confusion about gear oils and the API classifications. In this paper I will try to differentiate the two oils and clear up the mysteries that are flying all over the internet. It is extremely common, or normal, for all GL-5 oils to claim they cover the API GL-4 requirements for gear oils. This is a true statement. Does that make them satisfactory for synchromesh or synchronized transmissions? NO! They meet the GEAR OIL specifications, not transmission oil specifications. The API GL-4 and GL-5 categories do not mention or have anything to do with transmission synchronizers."
anamnesis

All very interesting. Three things just to play devils advocate and continue on the discussion...

Point one (which you are already considering): You are putting the oil in a diff, not a gearbox. So different kettle of worms with no synchros (obviously!)

Two (or 1b?): How much are you actually using the car and how much power is it putting out? GL5 isn't gonna crap out the thrust washers on a 45hp Sprite in 500 miles of use! Are you overthinking it all? (No offence meant, it is interesting to think about this kind of stuff, but end of the day going out for a drive is what it's all about!)

Three: The paper is 7 years old. Oil tech, like everything, has likely moved on.

Cheers,
Malc.
Malcolm

and---when you're driving along in a straight line the sun/planetry gears in the diff aren't moving on their thrust washers, not like a syncro ring that's probably rubbing on it's cone all the time

I'm thinking you're overthinking it
Just poke some 75-80 or whatever x 140 in it and drive it, if you have to pluck it out and replace the washers in 20 years time it's no biggy, you'll hear it clunking when it's time
William Revit

Combining all points, to further duscussion. 😉.

Good old saying that, "Over thinking". Like you can use your brain too much. Last I heard, not thinking enough, is a suspected culprit for dementia. But hey, chill, switch off, watch some soap or other, get stoned, have a drink or a drive, go out and see what you can find. 🤣🤣.


I bet they said the same to Newton, Voltaire, and esp' Einstein with his thought experiments. Stop over thinking it. Get a life, do something better with yer time, fer gawd's sake.

I should be so lucky to have such thinking prowess, 😅😅😅.

But seriously, I absolutely dismiss the premise of over thinking it. I am thinking about it. No more, no less.

Circa 3000 miles a year in my Sprite, more if I sell my Capri, and I don't pootle about, even near 70, I still cane it when the road is empty.

Yes diff not box. But diff with yellow metals. Both of which wear out, because they do turn under and with the gears, because both wheels are not always going at the same speed, hence why you can buy replacement thrusts and cups. My thrusts and cups are bronze or copper or whaterever.

Yes that paper is ONLY 7 years old, and the GL ratings are exactly the same still, and GL5, is still the same stronger bond compared to GL4.

Yes driving is what it's all about. And, however much I might also enjoy fixing it, if with a bit of over thinking, I can prevent it breaking so I don't have to fix it, I'll use my grey matter a whole lorra lorra lorra lot. 😉.

Esp', -- to remake a point I made recently, when I've just spent 700 quid paying for it ( diffs) to be fixed.

So, until I have definitive proof, that GL5 levels of EP, do not damage yellow metals in OUR diffs, I will keep thinking about it, and not use it.

And another point. The spec for our diffs is EP90, not 140. If built ok, they run fine on ep90. Why use a multi if not needed? Why use a gl5 just to be able to use a multi 140, when it shouldn't be needed?

What do points make? Ask Brucie. 😅😅

There. All that verbiage. I must be over thinking it. 🤣🤣🤣🤣

And for that matter, what are YOU doing reading and answering this? Why ain't you out driving? Lol

Where would we be without thought? 🤔



anamnesis

Anam,

Good the expert is willing to reply to your queries and worthwhile asking about the effect of the EP additives to items like the sun and planet thrusts. In https://en.wikipedia.org/wiki/Extreme_pressure_additive it mentions the EP additive reacting with the surface under extreme pressure situations and I can see that happening with the small contact areas with the gears but with the larger contact area involved with the thrust washers the reaction may not occur and not be an issue.

I have a couple of good condition steel sun gear thrusts but have only seen yellow metal, likely bronze, planet gear thrusts.
David Billington

I agree David.

I don't know if there is sufficient pressure on those washers/cups, to cause a problem using GL5 levels of EP. Clearly it must be, it IS less, than there is in tooth contact.

But synchro rings aren't under extreme pressure either. However they are under some pressure when gear changes occur, and like the thrusts in diffs, are subject to rotational/scuff forces. And GL5 is not advised.

Hence I also don't know that there is NOT sufficient pressure, to cause damage in diffs with soft yellow metals acting as bearing surfaces.

Planet, sun.
I read somewhere, that our diffs don't have planet and sun gears. Our cage gears are called something else. I may be wrong there. I've been trying to find where/what I read.

anamnesis

An .
No use ranting on here about using different oil
It was the so-called experts that f%&$ed your diffs and charged you for it, that initially told you to run 140

we are only trying to help you out here

and as far as
"And for that matter, what are YOU doing reading and answering this? Why ain't you out driving?"

Good point---i'm off for a drive down the coast, beautiful clear day--25c--lol

willy
William Revit

😃😃. You reckon I was ranting Willy? 😄.

Nah, as Crock Dundee might have said, that's not a rant, THIS is a rant. 🤣

https://youtu.be/dSnosk4tWrg

But yeah, I'm not impressed with the 140 idea or the reasons given for using it.

However, consider too, I started a different thread to my diff thread, for a question about mixing viscosity. Not to moan. Lol

How was the drive? 😁


anamnesis

Anam. What did yer man say was the best oil for type 9 ‘boxes?
Bernie.
b higginson

Hi Bernie

BGH Geartech say comma sx75/90.

The oil guy I emailed, said a good semi or fully synthetic 75/90 gl4.

I asked him about the original spec ford oil too.

I asked him, -- "Does this oil number mean anything to you? ESD-M2C-175A. Is it GL4 or 5?"

His reply:
"Yep, that would be Ford's Mercon. Today commonly a combined product with the GM Dexron Spec, so it will be Dexron III/Mercon, except that GM stopped licensing Dexron III, so it may be called "multi-trans" or something like that. You can also find it in a Synthetic that will cover the Mercon V spec as well. That is the same oil (maybe same transmission-built in their JV plant with Mazda).

He also replied and said Dextron/Mercron ATF or Mobil1 ATF if you want a good synthetic. It's primarily used in auto's, but the T9 five speed was designed with smaller synchronizers and surfaces designed for what ATF does. Even an auto has gears, but it has clutches too.

He'd previously mentioned Castrol syntrans, as had Nigel. So I tried the Castrol and then went back to the Comma oil.

The only issue I have is in 'winter', when running from cold, my first few shifts from 1st to 2nd, are a bit tight/slow. But if I run it on the drive first fir a few mins to warm the box a bit, it's much better, and then after a mile or so, it's ok. Summer no issue at all.

I believe the bloke at bgh geartech has his own 1st/2nd gear cluster and synchros made, to resolve this completely.





anamnesis

Anam. Thanks for such a comprehensive reply. You seem to have done what I did. I tried the Syntrans on Nigel’s advice and it was OK, but on reading that BGH recommend Comma, I switched to that. I made a drain plug on my type 9 so changing oil is easy.

I just filled my axle with an EP90 bought from Europarts, but I noticed that it is GL5 so I think I’ll get some GL4 and change it
b higginson

I think many/most of us have drilled a drain plug too. It's a good idea. In theory you don't have to change the oil, but I like to.

I guess the jury is still out on the need for gl4 in a diff with yellow metal washers, but I don't see the need to take a chance on gl5.
anamnesis

"And for that matter, what are YOU doing reading and answering this? Why ain't you out driving?"

Lol - touche!

Gotta do something to pass the time Mon-Fri, 9 -5.

Malc.
Malcolm

Gotta do something to pass the time Mon-Fri, 9 -5.


Ha ha. I suppose that could depend on if you are being paid to pass the time Mon-Fri, 9 -5. Or maybe, how much 😁.
anamnesis

Bernie, (anam),
up to you what you believe but for decades GL5 has been considered fine for use in the rear axle, and sold by MG parts suppliers.

I've many times put the information about the Ford spec ESD-M2C-175A, it's history and how widely it translates to more modern application in Ford specs and application.

BGH Geartech can recommend whatever they want and feel best to for use in their rebuilt boxes but I wonder how much testing they have done with different oils or are just sticking with what they know works from literally decades back, and that's fair enough it does work.

But I definitely found the Castrol to be better particular when cold (and it was GL4).



Nigel Atkins

anam, -

"The only issue I have is in 'winter', when running from cold, my first few shifts from 1st to 2nd, are a bit tight/slow."

Go back to the Castrol oil (or Castrol current equivalent ) then, just because BGH Geartech say Comma SX75W-90 GL4 as they have for 20+ years as an easy safety measure it doesn't mean you can't use a better oil (if you want to).

Richard Widman is in America with the oils available in American I doubt he's considered or tested the "claim" of the British oils I referred to.

It's all "oil beliefs" to me, some reports suggest x% of Americans believe they have been abducted (and probed as Prop might suggest) I wonder if Mr Widman might be in that group. 😀

(still miss me!?!).
Nigel Atkins

Knowledge trumps belief Nigel. 😁

I tried the Castrol, and went back to the Comma, because I found the cold gear change, 1st to 2nd, better than the Castrol. Nothing to do with Gl4. But Gl4 is important in t9 boxes.

As for the rear axle, I repeat, I don't know definitvely, if Gl5 is harmful. But equally, I don't know that it isn't.

Interestingly, the replacement large flat thrust washers, are now fibre, and hence the GL rating of oil no longer matters there. The cup washers though are still copper or what ever they are made of. And as I pointed out earlier, the fact is, that both of those types of washers are subject to a degree of heat and pressure, as evidenced by the degree of wear in them, and that they are replacable.

Plus, my diffs don't have the fibre washers. So why should use a GL rating above what's neccessary, if there's a potential to increase the speed of that wear?

Given that there are plenty of brands offering EP90 Gl4, I have no reason to experiment.

I wasn't aware mg parts suppliers had been recommending gl5 in our axles for decades, or that they are oil experts, or experts in general anyway, given some of the crap they are content to sell. Lol

You got something you don't like about our cousins over the pond? 😅😅


anamnesis

Are we being ripped off by oil companies, and I am referring to lubricants not fuel. Our Audi is now out of guarantee and the "service plan" has expired (the latter should read a quick flick over with a video camera). Audi Recommend Castrol Edge and I bough a 4 litre container of it along with a new filter on line. I have forgotten the cost but it was over fifty pounds. Whilst half way through thee job I realised I needed 4.5 litres. Oil used to be sold in 5 litre cans. Enough to fill the sump with some left over for top ups. I took our second car, the Sprite, out to Asda and bought a litre of their own brand oil, of the correct grade, for a few pounds. What would happen if I filled the Sprite with Asda engine oil rather than the overly expensive 20/50 Classic Oil. I could then do three oil changes a year for the same cost.

Jan T
J Targosz

Jan
I use Castrol Edge synthetic 0/30 in the V70 diesel which requires about 6 litres so I can buy 2 X 4l one time then 1 X 4l the next service (so I get 2 X 6l). But, as you say, it's expensive compared to mineral 20/50. I change the V70 oil less than once a year now as the annual mileage is low and I'm not convinced you need to change annualy.
Bill Bretherton

Why not buy in greater bulk?

20 litres at under 34 quid for 4 litres.

You'll eventually use it.

https://www.ebay.co.uk/sch/i.html?_nkw=castrol+edge&_sop=16&LH_PrefLoc=1&_pgn=4

****Edit. 0-30 is also sold in 20 litre drums.****

You're right too about the rip off aspect.

The original Ford oil for t9 boxes, was still available not so long ago. Maybe it still is. But it was 20 quid a litre back in 2012, and hence one reason for me using Comma oil. Esp' as the original Ford oil ESD-M2C-175A, and modern part number WSD-M2C200-C, wasn't considered any better at smoothing out the notchy gear changes in t9 boxes anyway.




anamnesis

Forgot to say.

Course we still miss ya Nigel.😁
anamnesis

"Why not buy in greater bulk?"

I've considered it but the car is getting on for a modern (2005) so if if was written off or engine seizes, say, it's not worth repairing and I'm left with oil I might never need. Also I do very low mileage in it now (we have a newer car as well for most trips) so I've lengthened the change intervals.
Bill Bretherton

anam,
which Castrol oil did you use as myself and others found the opposite of you, that is using Castrol Syntrans Multivehicle 75W-90 (GL4) improved cold gear changes, the Comma oil did not.

Are you sure you're not getting confused in your old age?

If it was just me that found the Castrol Syntrans Multivehicle 75W-90 (GL4) to be better that would just be my belief (or knowledge/experience) but others found the same and not just conservative Spridget owners but others with T9s in other MG models.

Have you checked Richard Widman is up to date with his knowledge of the gear oils now available to us in the UK, otherwise his out of date knowledge could just be his belief and his trumps could be the last suit and not current! I'm not got anything against Mr Widman I've no idea about him, he could be fantastic or a right piece of work, but I don't know either way so why would I dislike him.

I did like the devine Steve, e's over there, even if he wouldn't spend out a few cents on me.
Nigel Atkins

Round and round on a carousel, like the windmills of the mind. All just a case of history repeating the same things said before. Lol. I refer the honourable gentleman to the recent answer I gave before, just like the time before, and the time before that. 😃.

Nigel, I could look in the archives for the answer, as it was the same Castrol Syntrans we were discussing way back in ????, seem to think it may be as far back as 2014.

But even easier I'll check the Castrol bottle, because I kept it to use as a dispenser for the Comma, which I bought in a 5 litre plastic 'can'. I bought so much because I was rebuilding 3 or4 T9 gearboxes. I'll post a piccy.

Point.
The Type 9 gearbox was introduced in 1983. It required a GL4 level of EP. The way EP works, means GL5 levels of EP, 50% higher than in GL4, make the sychronisers in T9 boxes less efficient, and more subject to wear.

If you can show me, definitive proof that the API GL5 specification has changed, I'll happily reconsider.

Not an email reply opinion from a customer help rep', who says their oil GL5 oil is safe in a GL4 specified gearbox. But a technical description, explaining why, GL5 EP is no longer a problem to brass synchronisers and yellow metals in general.

Do not include the now redundant fact that GL5 EP is no longer corrosive. That is not the issue. 🙂.

I remain sir, your old aged 'onerable rabble, and await yer speedy response. 😅.

Meanwhile, I'm happy with the Comma gunk in my box.

I was only asking about viscosity in my diff. 😉.

I didn't want to blow the whole thing up. 😅😅

https://youtu.be/7_PX1cVuaVA

Still, mustn't grumble. Gives me summat to chew on while I'm layin' abaat wiv covid. Lol.






anamnesis

Here you go. I left me sick bed and crawled on all 4's to me cold garage, just to get a picture of Catstro's finest cigars. 😁.

We smokin' the same stuff?

Well not now of course, coz I quit. Lol



anamnesis

Does the Ford type N (9) gearbox require a GL4 oil?

This is the kind of thing I call proof.

Ford original part number for the oil. A83SX 2C175-AA aka Ford M2C175-A.

Ford M2C175-A
API GL-4 grade, SAE 80W90 gear oil for Ford Type N transmissions made before 1990.

https://www.oilspecifications.org/ford.php

Now if GL4 is redundant because GL5 has been altered, and replaces GL4, Ok; Show me the API's text that describes what changed and when. .

But if GL5 has been altered, and replaces GL4, why is GL4 still being made?

BTW.
https://www.oilspecifications.org/

Brilliant source for information on oil.



anamnesis

Sorry to hear you've got Covid it's obviously dulling your brain as yes we (you, I and others) have been all through this many times before and I may well have provided some of the info and links you've now put up.

I hope you don't get Long Covid or you could be repeating all this ad infinitum. 😁

Not long ago there weren't vaccines for Covid (19) but then there were, things change and progress, same with oils. 😁

You use what you want (best it's legal though).

If you want to be really 'right' then you can still get Ford 75w90 Transmission Oil – 1790199, just one example from an eBay seller. - https://www.ebay.co.uk/itm/253683005814

I hope you fully recover soon.



Nigel Atkins

Yer still missing it Nigel.

Yes oils change.

Has the API changed the GL5 specification?

If so, show me.

I don't need to change oil. I'm happy with the Comma.

And what's the GL rating of that Ford gear oil you linked to? Are you suggesting it's the same as the original Type 9 Ford oil?

Even if it is. Just another repeat as I've said before. The orginal Ford oil was circa 20 quid years ago. Your latest suggestion is 30 quid.

Comma is less than 10 quid from Halfords.

Covid up Nigel. 😁




anamnesis

Clever Nigel.

You tricked me by repeating what I posted earlier. My covid brain didn't notice. 🤣

WSD-M2C200-C is indeed the original type 9 oil. Albeit now 30 quid instead of 20 quid, as opposed to Comma under 10 quid.

Is this your recommendation now for Type 9 boxes? Why not before?

Anyway, straight from the Ford horses mouth, IT **IS** A GL4 OIL. Just what the type 9 box ordered. Lol

So what exactly is this debate about?

I really don't know what point you are attempting to make Nigel. 🙃

https://www.msds.ford.com/cpc/productDetails.asp?pgn=8&FIRNo=144844&cookieConfirmed=true






anamnesis

the debate is about using GL5 oil in a hypoid diff that it's designed for-
Your diff guru wants you to use straight 140 gl4 which isn't such a good idea
The ideal would be a multigrade 8o(ish)x 140 but you'll struggle to find that in GL4 which has become more of a transmission oil choice
Your best option is a good brandnamed 80-85 x 140
Forget about sulphur eating your rear end, all quality branded GL5 gear oils have had buffered sulphur for at least 20 years so that GL5 can be used in axles - transfer cases etc with brass bits
Honestly you are overthinking it-
William Revit

Nothing to do with ep being corrosive Willy. Yes, I said earlier it's buffered now. That's not the issue. Not repeating everything I wrote again, other than to repeat I don't need any better than a good ep 90, plenty of that about. I've never had a problem with ep90, and I had very many miles before needed my diffs rebuilding,

If they needed 'better' than ep90, I'm sure it would have been raised here or elsewhere before.

So it's all moot I reckon. 🙂.
anamnesis

got your diffs back yet--------I'm a bit cynical--I reckon they knew they weren't set up spot on and that's why they were pushing the 140
William Revit

Willy, I'll answer/update in my Diff thread. I shoulda stuck to one thread. Lol.
anamnesis

So, EP90 it is. I'm guessing that's what the rest of us use....
Bill Bretherton

I noticed the difference in 'drag', when I tried a 140 gear oil. So back to viscosity, with particular regard to ---

"Understanding Lubricant Churning"

"Bearings and gears require a certain amount of force to begin turning and to continue turning once they are set in motion"

"Running torque is usually less than starting torque. These forces are variable depending on several parameters."

"Lubricant churning -- occurs when the bearing or gear must churn through the lubricant as it performs its regular task."

"If the lubricant level is too high, ----- the machine must work harder to push through the added lubricant. This is the basis of that churning condition."

VISCOSITY.

"Besides the lubricant level, another variable is the lubricant being used. Since the most important physical property of a lubricant is viscosity, the proper viscosity must be selected according to the speed, load, temperature and general running conditions of the machine. If the viscosity is too thin, then excess friction due to metal-on-metal friction is generated, causing machine wear and premature failure. If the viscosity is too thick, this leads to viscous drag, which causes very similar issues as having a lubricant level that is too high. Neither of these situations is desirable for the equipment."

https://www.machinerylubrication.com/Read/30520/understanding-lubricant-churning

anamnesis

Measuring oil viscosity, --- at home.

"The process is a complicated and potentially dangerous one, and so should not be undertaken without extreme care and the correct equipment and safety measures:

Fill a container with water and boil to 100°. The water should be deep enough to submerge an object, but not overfilled so that it will spill. Maintain the temperature throughout the test.
Submerge an open-ended U-shaped glass tube in the water, so that the bend is submerged, but the ends are open to the air.

Seal one of the ends of the tube. Pour the oil into the open end. Using a stopwatch, record how long it takes for the heated water to raise the oil’s temperature enough that it rises to the sealed end of the tube. When it reaches the end, remove the seal and record how long it takes to fall. The longer it takes for the oil to rise and fall, the more viscous the oil. "

https://www.petro-online.com/news/fuel-for-thought/13/breaking-news/how-to-test-oil-viscosity/31399

Sounds like fun.

anamnesis

Uh?
Surely if one end of the U tube is sealed, it will create an air lock and the heated oil isn't ever going to rise up there?

Perhaps I need to re-read the recipe!
GuyW

Also An. -coming into play if using a higher than optimum viscosity oil is cavitation- this will absolutely wreck the gearset, possibly more so by running incorrect oil than by running oil with contaminants like water or foreign particles-which also cause cavitation.
This is where multigrade oils come in if you need a thicker/higher temp oil for normal operation.

willy

Here you go ,i found this for you--cavitation and this will happen if the lubricant is too thick, has water in it or debris in the oil---and it will absolutely wreck the surface of the gears

https://www.youtube.com/watch?app=desktop&v=FKaUooCrb1g
William Revit

Thanks Willy. I've been looking for stuff on cavitation.

I knew you explained it before, but it gost lost in everything else, and I couldn't find it again.

It illustrates how experimenting with oils, can have bad consequences if you don't fully understand how oils are designed and chosen for a particular aplication.

Dossing around, largely in bed, with this covid lurgy, has given me oodles of time to read all about oils. And what an interesting, but massively complex subject it is. None of which I've ever needed to know, and probably still don't know or need to know. As just sticking pretty well to the good brand reccomended oils for the last 50 plus years, for all my cars and bikes, has never caused me a problem. 😅.

anamnesis

This thread was discussed between 23/02/2023 and 05/03/2023

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