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MG MGB Technical - Engineoil

Can anyone advise on the pros and cons of using a fully synthetic motor oil in their cars.
My BGT is used on a daily basis and I have been offered a qty of Mobil 1.
Previous information suggests this is not a smart move.
Comments please.
Regards
Graham
G Withnell

Synthetic is a superior product but its benefits are not normally needed for a road car.

M1 0W40 is a little on the thin side for older engines but the 15W50 should work well.
Paul Wiley

I believe others were commenting that their engines leaked a lot more with synthetic oil.
Sam

Synthetic oil is far better than standard motor oil.
However, it get dirty like any other oil. That's what causes wear. So, you spend a lot more when you should just change it anyway.
Kelly Combes

Grahm,
This thread on the TD-TF board completely changed my thinking on oil for our cars and indeed changed the thinking of many of us. I am surprised it wasn't brought up to you sooner:
http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&mode=archiveth&archiveyear=8_2007.dat&access=&subject=8&subjectar=8&source=T&thread=200610090226352026

Steve
Steve Meline

I would strongly suggest you do NOT change from standard oil to synthetic on anything but a new engine. Synthetics will knock loose a lot of crud that standard oils won't / leave behind, and these chunks will end up circulating through your engine. NOT good!
Steve Simmons

Modern low viscosity oils are intended for modern engines with very small clearances, not like our agricultural engines even when new. By allowing more metal to metal contact they could actually be detremental. They will also leak out of every orifice in sight, and all those out of sight, as they are so much thinner. I did try Castrol Magnatec 'for conventional engines' (their words, i.e. not injection) but found no difference in oil pressure. And as the engine has run for coming up to 200,000 miles on conventional oils the much higher cost of Magnatec (doubly so as it is only 4 litres in the can as opposed to 5 in most other oils) just wasn't worth it to me.
Paul Hunt 2

Modern synthetic oils do not have to be low viscosity, they will thicken less when cold but thin less when hot above 100c, thus an equivalent weight synthetic will have the opposite effect re metal to metal contact and if esters are used the load carrying ability will be even greater.

All oils rely on additives to prevent metal to metal contact (ZDDP) and as detergents and dispersants so there is little difference between synthetics and mineral. However some synthetics do use esters (Magnatec also claim to use these for "cling" as esters are polar) as a base oil and these may have a cleaning effect, Mobile uses about 3% and may also use conventional group 3.

In order to improve oil quality mineral oils are now highly refined to an extent that a group 3 mineral oil is very close in performance to PAO and in the US they can be classed as Synthetic. Usually a mineral will be a group 1 and group 3 mix in UK and group 2 and group 3 mix in US, so even so called modern minerals are close to being synthetic.

One major difference between a mineral and synthetic oil is because of the ablity of synthetics to thicken less when cold and thin less when hot, they do not need to use additives as pour point depressants and viscosity improvers, which means more oil and less crud. Minerals use say a 20wt base oil add PPD to allow flow in cold and viscosity improvers to maintain oil pressure when hot.

ZDDP also has to protect a mineral oil and is consumed in the process.
Paul Wiley

As the word synthetic suggests, the oil is produced such that at the molecular level, one molecule is bonded to the same size molecule. This means several things on a functional level...
1. It is harder to break these bonds. With conventional oil, "mother nature" isn't as discreet at bonding different size molecules and HEAT will break these bonds more readily so that there a faster break down in the oil and less engine protection...hence the "3000" oil change.

2. With uniform molecules, you get more uniform coverage in even those "not so small" clearence areas of our old MG engines....if you feel viscosity is an issue for "cling" and protection, do what I do...use a 20w50.

3. Ability to resist change in "pour point" either hot or cold...which means more consistent lubrication.

All of these concerns are valid ones but if you balance the right "weight" with the right oil type (conventional / synthetic)...it'll work great.

If you're worried about the cleasing effect, from the first few use of synthetic, get a good filter and change it after a few thousand miles...it'll help keep the system clean.

Ramneek

I have been using Mobil 1 15W-50 with what appear to be good results. No leaks, and better hot idle oil pressure than I had with conventional 20W-50. Of course your mileage may vary.
David Wagner

I've run both and don't see much difference in real life.
The big issue is with modified cams and shortened lifter and cam life.
Because zinc kills catalytic convertors it is no longer in road oils - petroleum or synthetic-.

Competition oils for off road are still available with zinc. There ain't nothing as good as zinc for ep lube.
diesel engines don't have catalytic convertors and they still have zinc. I run Chevron Delo diesel engine oil 15-40 to protect my cam and lifters. It works great. There is a bunch of discussion on this subject back in the archives.

At least run it as a break in oil to protect the cam and lifters during the initial run in for the first few thousand miles.

Barry
Barry Parkinson

Barry

Phosphorus is being REDUCED in both Car and Diesel oils but applies to certain oils only. Zinc is the Z in ZDDP.

TITAN GT1 for example is the first (probably only) zinc-free engine oil on the market but it still contains phosphorus.

Esters are used in top quality synthetics.
"Cling" Polarity means that the ester molecules have a positive and negative charge. This causes the ester molecules to be attracted to each other and stay together as a liquid longer at high temperatures. Polarity causes the ester molecules to be attracted to metal where they form a tenacious film on the metal surfaces. For oils this means greater film strength, lower friction, higher lubricity, and less energy consumption.
Paul Wiley

Paul
I don't disagree with you as to zddp. Diesel engine oil does contain more zinc and in a form that is more effective than the zddp formulation which is designed to avoid fouling catlytic convertors.

If you take a look at the sheets for oils showing the % zinc and other additives in engine oils you will see levels of zinc additives much higher in industrial engine lubricants than gasoline engine lubes.

In California, oils are available for off highway competition use that have high levels of zinc that are not permitted with pollution controlled (read "catalytic convertor") engines.

By the way, several of the diesel oils also meet the current standards for gasoline engines as to detergency, chemical buffering etc. I've run Chevron Delo 15-40 in my B with great success.
Barry
Barry Parkinson

A newer type of zinc antioxidant/AW additive is Zinc dialkyldithiocarbamate, but it is the phosphorus which is being reduced.

Which type of ZDDP is being used in Diesel and not PCMOs?
Paul Wiley

Paul
I don't know what brand(s) you are specifically referring to. In past discusions it was learned that the US additive formulations re zinc is different than some European oils. Europe does not appear to have the same degree of restrictions on zinc additives.
Barry
Barry Parkinson

Barry

There are two types of ZDDP used a primary and secondary, slightly different ratio of Zn to P and activate at slightly different temp/pressure.

The main difference between US and Europe is that the US is CAFE driven and not only are thin oils recommended but these are designed to shear and thin more in use for mpg gains.

Diesel engines do not show the mpg gains with thin oils and usually in Europe an HTHS of 3.5 is recommended, which means that European oils tend to be xxW40 or above and dual rated.

The US also favours cheap mineral and 3k changes. The anti wear system of oil going from cold is flow, esters and ZDDP. ZDDP does require time to activate in new oil and this can cause a blip of additional wear when changing, although regular changing is necessary with cheap mineral to avoid varnish and sludge.

Apart from the US recommending thin oils these thin SM oils also now have reduced ZDDP. This reduction in ZDDP in US appears to have spilled over into some of the US thicker oils. To help deal with reduced ZDDP a number of newer anti wear additives are being used normally as esters, so the SM oils may be overall a better product ie a Diesel oil may well fail the latest SM tests,
but these oils may give problems with older/modified engines.
Paul Wiley

Paul,

You say that: "ZDDP does require time to activate in new oil and this can cause a blip of additional wear when changing".

I remember reading somewhere that for some reason, engine breakdowns are more common just after an oil change. I suppose this may be the reason? How long does it take the ZDDP to be fully activated?

Tore
Tore

Tore

engine breakdowns are more common just after an oil change may be linked to ZDDP activation but I've not seen a direct reference, maybe within the first 1,000 miles but dependent upon oil temperature as ZDDP decomposes and becomes active at certain temperatures.


(further inquiry suggested that the result was not so surprising, as many oil chemistries require time and temperature to enhance their effectiveness).
http://www.swri.org/3pubs/IRD1999/03912699.htm
Paul Wiley

Very interesting. This may give me yet another reason to remove the oil cooler from my MGB. I suspect that in the Norwegian climate and at my usual moderate cruising speeds, the oil in my three-bearing engine is just too cold to give its optimum performance.

Tore
Tore

Tore-
Install a 200° Fahrenheit thermostatic bypass valve as overcooled oil can rob power and lead to accelerated wear. Because overcooled oil is thicker than it would be at normal operating temperatures, the piston rings will “hydroplane” over the oil and, on the upward stroke, scraping it into the combustion chamber where it will be burned, leading to carbon deposits and an increased risk of preignition. An excellent thermostatic bypass valve with ˝” NPT threads is available from Perma-Cool (Perma-Cool Part # 1070). Perma-Cool has a website that can be found at http://www.perma-cool.com/ .
Steve S.

Tore

Additive activation is usually considered approx 60c, however localised pressure increases temp to activate ZDDP.

Core temperature plays a big part re wear

"Wear tests with neutron bombarded compression rings in fired engine tests including a gamma ray spectrometer have shown that the piston ring wear rate during the start-up period was up to 45 times
the steady-state wear rate, and that approximately 84 % of the ring wear occurred during
the first approximately 22 minutes of operation (Perrin et al., 1995)."

Unless you have high oil temps then a cooler should not be necessary, and for a Norwegian climate a 0W/5W 40 should work well.
Paul Wiley

I agree with Steve S. The new synthetic oil will not only knock loose all the built up crud thats already there but it will also cause leaking problems.Myself I prefer Castrol 50wgt racing oil.
John B.

This thread was discussed between 25/03/2007 and 11/04/2007

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