Robert Linton

For track use, would you use Kendall GT-1 20W50, a mineral based oil, or Mobil 1 15W50, a synthetic oil, or Castrol RS 10W60, a synthetic oil, and why? And for street use which one?

John.

If you have a turbocharger, you should really be using synthetic oil. The temps in the turbocharger bearings can turn conventional oils into garbage in no time. I run Mobil 1 15-50 all year long (in my turbo 928 and Audi S4( and have had no issues with it.

Julian Allen

Robert, I'd use Mobil 1 15W50 year round, street or track. I change my oil about every 15 hrs for track use, send it to the oil analyzers and never had bad metals in the oil. For me, success like that is good enough for the long term.

Robert Linton

No question but that the synthetics are fine products. However, assuming you change oil after every track event, is it possible that the Kendall (maybe even a straight 50W) might not provide better protection - particularly for the camshafts ?

Pete.

Why not use Mobil 1 0-40 that Porsche recommends?

Robert Linton

For street use, i.e., lowest fuel consumption and maximum efficiency (least oil changes), I would go with the 0W40 (for the mileage) and a synthetic (for the longevity). For best protection in racing conditions (which assumes a high level of engine maintenance, the least of which includes changing oil after every race), some professional racers and engine engineers might suggest that the GT-1 might offer better protection.

FixedWing

Bob,

The presumption is that "racing" is somehow harder on the engine oil than non-racing. But why? Flat out at max RPM is the same whether you are on the track or off. The engine oil knows no difference. But you will change your oil regularly as compared to the street user so many of the issues that they face will never be faced by you. You don't have to worry about contaminants, condensation, corrosion, etc.

If anything, engine oil faces an easier time in racing than it does in street use.

I would argue for going in the other direction. Use a lighter weight oil and not a heavier one. The reason is simply that you will get more power from an engine with lighter weight oil. The heavier oils tend to increase drag within the engine.

I've heard that in F1 they use special 0 weight oils for qualifying for this reason. Now, you aren't going to rebuild your engine after every session like they are and your manufacturing tollerences are probably not as close as theirs are so you probably don't want to get that crazy.

But I would say that you could use more aggressively thinner oil than the street user can. Either the oil works (seperating moving metal parts) or it doesn't. I'd start with 0W-40 and maybe even go for 0W-30. A 50 or 60 weight seems to be going in exactly the wrong direction.

I understand that the synthetics offer a clear friction advantage as compared to mineral based oils. I've heard 1-3%. All synthetics are not created equally. My personal preference is Mobil One.

So, if one were to design their own racing oil it would probably be a single weight, lightweight oil with none of the additives for corrosion, contaminants, etc. Lightweight for low friction, single weight as the additives they use to extend the viscocity range aren't lubrcants at all and none of the other additives for the same reason. That oil would be a synthetic. In other words, exactly what F1 uses with their 0 weight oil (though probably a heavier weight). Unfortunately, I have never seen anything like this offered commercially. But maybe it exists and could be got if asked for.

Interesting article:

<a href="http://www.caranddriver.com/xp/Caranddriver/columns/2000/November/200011_columns_bedard.xml" target="_blank">http://www.caranddriver.com/xp/Caranddriver/columns/2000/November/200011_columns_be dard.xml</a>

And another one:

<a href="http://www.audiworld.com/tech/eng14.shtml" target="_blank">http://www.audiworld.com/tech/eng14.shtml</a>

S.

FixedWing

Just saw that you posted your message everywhere!

So is it an air cooled engine? Air cooled engines are known for having different expansion rates of the various parts with very low clearances when cold. So again a thinner (or at least a low "W" rating) would be advantagous.

Also, will the car run on racing fuel? If so, is this leaded? Synthetics are known to not be able to hold lead contamination in suspension very well.

This is why there are no fully synthetic oils in aviation (100LL has lots of lead). The best at this moment are semi-synthetics for this reason (Shell Aviation 15W-50 and Exxon Elite 20W-50).

This argues for the use of a mineral based oil or at least a semi-synthetic but I would think if you changed your oil very regularly as you intend then this would not be an issue.

S.

Konstantin

on a recend test in a german magazin the Castrol 10W-60 was a sgood as all others at 100 degree and 3 THREE times better at 150 degree.

All other brand name oild were almost as good. on lower temps the 0W-30 ils were better but atb higher temps nothing wa sas good as the 10W-60.
evne the 0-40 Castrol was a sgood as the Mobil 1 but nowhere close to the 10W-60.

I use it for years and never had problems. I run boost up to 1.7 bar (25 PSI) and the cylinder walls pistons tec are all like new after 230000 km.
The toyota used it in the Le Mans GT1 too.
BUT... newer engines requires thinner oils.
if you race the car get the 10W-60 other wise on a cold weather the 0-30 is ok. It doesn't matter if it is Castrol, mobil or what ever. if Porsche recomest it (and the have about 20 oils in their list not only Mobil) then it is good enough for the street.

Konstantin