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MG MGB Technical - Synthetic Oil Weight

I plan on switching to a synthetic oil in my 18V with about 10K miles. Looking at the options I see that most brands are available in slight variations from SAE 5W-30. I have been using Castrol GTX 20W-50 non-synthetic. I could only find one synthetic in that weight, Valvoline. This may be somewhere in the archives, but what is the best weight for a synthetic?

I also saw a few "synthetic blend" products. A little cheaper, I assume they; are some type of ˝ & ˝ products and ˝ as good. Do you agree? I will also run this on the MGB Technical board. Thanks.
Steve
Steve Meline

Why do you want to change to synthetic? I always gathered (and I could be wrong here) that in older cars with looser tolerences synthetics didn't actually offer any gains but have the downside if being more expensive and more likely to leak out! I figure using standard (and cheap) Castrol GTX and changing the oil and the filter regularily will work fine for our engines.

Simon
Simon Jansen

Valvoline is also the only 100% fake oil I've seen in the 20W50 wt. for a standard road use oil. Many older cars count on the HC vapors from the oils to help with swelling seals and the like and often switching without using all new seals, gaskets etc. can lead to an added dripping and leaking from the motor.A reasonably maintained MGB motor will run fine for 100,000 + miles before a rebuild. How far did you want to go?? If you want the added protection of some of the man made slicky things in synthetic oils try adding some of the STP, or Lucas oil type additives to the crankcase.
G. Wayne Hardy

Steve
If you look in the archives you'll find a lot of stuff on synthetic oils, etc.
Barry
Barry Parkinson

I am running Mobil 1 15W-50 with good results. No leaks, and good oil pressure at both idle and above. This in a 1979 B with 67,000 miles and that does not appear to have ever been overhauled.

David Wagner

Steve

Oils rely on anti wear additives usually zinc. With an old style engine high zinc is beneficial but has the potential to poison cats on newer cars and so is being reduced in the low weight energy conserving oils.

High weight, Race oils, motorbike oils and diesel oils usually contain high zinc.

Oil recommendations are at optimun at normal operating temp, so all oil is too thick when cold and too thin when hot. Synthetics thicken less when cold and thin less when hot and this is one of their advantages, but outside usual operating temps. Because basic mineral oil cannot adjust to cold and hot tempeatures, viscosity improvers are uesd and these breakdown quickly hence one of the needs for frequent oil changes with mineral.

Semi synths are basic mineral with 10-20% synth to make the grade.

Fake synths are group III oils and are highly refined mineral (craked) and have similar performance to standard PAO synthetics.

Synthetics are a mix of Group IV oil (PAO) and group V oil. Group V is usually ester oil, highly advertised in Castrol start up, but are used in most race oils such as Redline Motul Silkolene. PAO tend to shrink seals and esters swell one reason for balance.

Ester oils are high performance oil, for example the viscosity of redline 5W20 is nearly the same as M1 0W40 at 150c.

Different parts of engine may require different viscosities and oil viscosity is a compromise, however the W number is at artic conditions but does indicate the oil flow at colder start up temps, a 5W50 being preferable to a 20W50.

STP and Lucas basically thickens oils and adds anti wear additives fine in the old days but the right oil to suit circumstances is the better choice and an ester base 10W60 is available in the UK if required.

A 15W50 M1 should stay in grade for 15k miles.

Paul

Have used synthetic Mobile 5-30 wt. oil in my '74 1/2 GT for a while and it sounds better, oil presure is great and have had no leaks. Car sat for two years and started right up. Been driving daily now and swear by the Mobile synthetic. I change it twice a year.
JOHN
JW Colson

Paul
Thank you!
Finally, someone on MY side.
Paul do you have Amsoil synthetic available in the U.K?

SF
Dwight
DCM McCullough

I've used synthetic oils going back to the '70's. My experience modernly is that conventional oils are way better than they used to be in comparison to syn oils.


Because of fouling of catalytic convertors, zinc has been eliminated from most modern oils including synthetics. There is no equivalent replacement product. In Calif, the only oils with zinc are "illegal" off road racing oils, and diesel engine oils. The 15-40 diesel oils are rated for auto & industrial use, contain zinc and will protect your valve train much better than any conventional or synthetic oil.

With a modern engine with it's minimal oil use and closer tolerances - my experience is that synthetic oil consumption is less than 4 oz (US) in 8 to 10 k miles. In my MG with loose exhaust guides with no umbrellas/seals, The engine uses more oil in 500 miles than 10k in a modern engine. The increased engine oil life is really not an issue when you are adding a quart of fresh oil periodically in any event.

Oils improved dramatically from '64 to the mid '70's. The mgbs had oil coolers fitted in the US because 1/ overdrives were too expensive to sell and 2/ The engines failed when driven in hot weather at hi rpms. By the mid 70's, the factory reduced the oil sump capacity, eliminated the oil cooler, and ran the engine way hotter for smog control purposes. No problem with the new oils. Oils have improved a lot more since the '70's.

Bottom line from my point of view. If I were racing I would pay the extra $ for synthetic for some reduced friction and extra hp, or if I had an engine that needed no oil additions for 10K miles. If I had a high performance valve train, I would use 15-40 truck oil, and otherwise, a good quality major brand modern oil.

Barry
Barry Parkinson

Dwight

Is available and is a very good oil.

http://www.opieoils.co.uk/performance_lubricants/

Barry,

The only oil I am aware of with no zinc is 0W20 Fuchs oil, used in Porsche Cup racing.

Paul

Paul

In the US zinc is a no no because it kills the catalytic converter. I had a good friend who worked in the oil labs for one of the major oil companies. They tried all kinds of stuff as additives to replace zinc for ep purposes. Nothing that didn't damage catalytic converters came close. Roller cams in the new cars helped longevity and performance, and became universal in GM cars. Overhead cams have less ep and are more lube tolerant.

The good old pushrod MGB needs every bit of lube help it can get for those lifters and cam lobes, especially when modified to hi lift and longer duration, and working against heavy duty valve springs.

35,000 to 40,000 miles may be acceptable for an antique. It won't do it today with 100,000 mile warranties.

Barry

PS In Calif you can buy racing oil that is legal only for offroad unregistered vehicles. It is oil with zinc.
Barry Parkinson

Barry,

Virgin Oil analysis for Mobil, I assume available in Calif, the first two are energy conserving, "reduced" Zinc
5W30 10W30 EP5W30 EP10W30 R

Zn 775 858 1058 1002 1536

Is there a ban on race oils like Redline?


Paul

Barry,

This is from Penrite site which may help to clarify position re Zinc and the older car.

An engine oil that contains about 0.1% phosphorus or higher, will easily provide the required anti wear properties for older engines.

The step from API SH to API SL was accomplished by a combination of new additives or adding additional anti wear and anti oxidant to existing blends. These were not phosphorus based, but used organic molybdenum additives (not molybdenum disulphide - aftermarket oil additive), to keep phosphorus levels at 0.1%.

Now we have API SM – for the first time, the limit on phosphorus is from 0.06-0.08%. There are industry concerns about the applicability of these oils in older engines. However, the limit only applies to 0W-20, 0W-30, 5W-20, 5W-30 and 10W-30 oils (so called “ILSAC” grades). Any other grades are exempt from this.

Therefore even blanket statements about API SM oils will be incorrect and further research will be needed by the end user.

There is one other factor with non-ILSAC oil grades. If they also have the European ACEA A2/A3 with B2/B3 or B4 performance levels, phosphorus levels will also be at 0.10 % to 0.12% as their tests have been more severe than the API for some time. Hence an oil that is SL (SM)/CF/A3/B3 also well exceeds the anti-wear requirements for older engines.

The irony is that API SF and SG oils formulated in recent years usually have phosphorus contents of around 0.08% (usually 0.1% maximum) anyway due to other advances in technology, unless the blender chooses to add extra additive
Paul

Several years ago I read an artical that stated that motorcycle oils from Honda, Yamaha, etc. were still made with the additives that they had taken out of automotive oils due to polution laws. Bikes still don't have cat's on them so this may still be true.
John H

Paul
It is my understanding that Calif regulations prohibit certain additives in fuel & lube oil that will damage a cat converter.

They are legal if labeled for off road use even if they have too much of something. Redline doesn't seem to address this issue in their promotion, although I haven't checked there web site in a while.

For instance, you used to be able to buy a Lifter Lube product that was supposed to help with sticky hydraulic lifters. It had solvents and lots of zinc. Now it is just solvents - no zinc.

Some companies attempt to convert the ban to a marketing tool by conspicuosly labeling the product for "Off Road" use only. There are lots of oils labeled for motorcycle use only. No Cats (yet) are required for motorcycles.

Check the zinc levels in industrial engine oils and you will find close to 1%. The stuff works. Million mile truck engines are proof.

Barry
Barry Parkinson

Barry,

I assume you refer to HDDO ie
http://www.amsoil.com/storefront/acd.aspx
if so the Zinc is 1028ppm per VOA

Most HDDOs will be the 1000-1300 range bike oils maybe a bit more and race oils usually higher again, the highest level I've seen is a race bike oil.

This Amsoil bike test does cover Zinc levels and anti corrosion aspect which is usually good with Bike oil as not often used as daily riders/drivers
http://10.45.0.106/768811076/663578784T060607132926.txt.binXMysM0dapplication/pdfXsysM0dhttp://www.amsoil.com/lit/g2156.pdf
Paul

Paul
I don't know about the Amsoil site. Check with Chevron, etc on their industrial oils and they have tech sheets whitch disclose the amount of zinc. Most are right around 1%
Barry
Barry Parkinson

Barry

Are you looking at the Safety Data Sheets? If so for GTX the ZDDP (Zinc/Phosphorus) is 1-5% http://www.conocophillips.co.uk/NR/rdonlyres/4BFA3C04-A644-4102-826B-918B3AF082FC/0/GTX_Mag_10W40.pdf



Paul

Paul
Yes, the safety data sheets seem to be the only public disclosure of some of the oil additives - especially zinc.
Your research is demonstrating that oils are different depending upon local laws and regulations.
I've only done the Calif research, because that's where I buy oil.
Barry
Barry Parkinson

Barry,

Oil formulations can change quickly for example post Katrina.

The US market use some good Group II and III mineral oils but synthetics tend to be cracked mineral oil excluding the known true synths. The US oil craze is to find Green German made Castrol oil, true synthetic and its own unique ester.

The Delo also has moly so a stout additive pack.
Paul

This thread was discussed between 22/05/2006 and 07/06/2006

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