Hello,

I drive a rally spec car with 2.0 litre 300bhp engine.I dont rally with it but used only as a sports car.
I am using Mobil 1 0W40.
I am thinking of changing to 10w50 which is not synthetic but a Group III oil because car owners handbook says that 0w40 can only be used from 20 degC to -35degC,I guess that they are refering to mineral oils which have a lot of viscosity improvers that might shear douwn quickly for this types of oil.
I have seen other car handbooks that allow 0W40 from -40 to +40 degC.
Do you think that the thicker oil will give me better protection in the hot summer days? +38degC

Hmm. 2 liters... Impreza, Corolla or Evo? (all good!)

Mobil 1 is a good oil but if you're searching for a higher summer viscosity, try a 5W-50. Then you have a better lubricity at low revs and cold start as a 10W, but also have the better summer characteristics.

With that spec I assume turbo, I would lean towards an ester content oil. Silkolene has 20% esters with PAO so fits nicely with high performance on road rather than track. Motul also have this sort of blend otherwise M1 or Castrol true synths.

I can't see a problem with M1 0W40 (HTHS is high) assuming your recommended oil is not more than a 40.

quote:

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Originally posted by Frixos:
Hello,

I drive a rally spec car with 2.0 litre 300bhp engine.I dont rally with it but used only as a sports car.
I am using Mobil 1 0W40.
I am thinking of changing to 10w50 which is not synthetic but a Group III oil because car owners handbook says that 0w40 can only be used from 20 degC to -35degC,I guess that they are refering to mineral oils which have a lot of viscosity improvers that might shear douwn quickly for this types of oil.
I have seen other car handbooks that allow 0W40 from -40 to +40 degC.
Do you think that the thicker oil will give me better protection in the hot summer days? +38degC

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Yes, thicker oil will give better protection in the hot summer days if the engine oil that you use contain excellent shear stable VIs ( VIs shear stability index is in the range of 20-25)

the difference between 10W 40 and 10W 50 are viscosity at 100C. The typical vis for 10W 40 is 15 and for 10W 50 is 17.5 - 18.0. You will be paying more for 10W 50 oil for higher content of VI but 10W 50 can cover 10W 40 temperature range also but not vice-versa.
Kumar
kumartr2@yahoo.com

M-1 0W-40 should do an excellent job even at high temps but if you are worried about heat degradation, why not switch to M-1 Super Synth 15W-50 which will give you the high temp viscosity, I have used it in racing as well as rally conditions and in my Honda RC45 Superbike with fantastic results, it is shear resistant and stable even when the engine has been pushed to the upper limits of temperature.

Can you get Redline Oil? It is supposed to be mostly ester and they state you can actually run one viscosity grade lower than you would with conventional oil. Also, most of the Redline is multigrade without any viscosity index improvers, I think all but the 5w40 are like that. So it is pretty robust stuff.

Thanks,

The only true synthetics I can get here are Mobil 1 0W40,Motul 300V 15W50.I have found also a product from Total lubricants 10w50 and they mention in there specs that the base oil is PAO,
and is reasonably priced.I might try that.

quote:

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Originally posted by Frixos:
Thanks,

The only true synthetics I can get here are Mobil 1 0W40,Motul 300V 15W50.I have found also a product from Total lubricants 10w50 and they mention in there specs that the base oil is PAO,
and is reasonably priced.I might try that.

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Yes, you can try 10W 50 grade oil, it should perform reasonably better.

Kumar
kumartr2@yahoo.com