Engine oil viscosity is determined by clearances and orifices. Thicker oil can and will cause problems in areas like lash adjusters as the bleed holes are designed for thinner oil.

 

I think you are right, it's cut and dried. Besides what would be the advantage of changing the oil anyway? I guess any fully synthetic oil of the appropriate viscosity and the correct specifications will work just as well but Mobil 1 is easy to find and can be gotten at relatively good prices so I don't see a good reason to change.
FWIW, Mobil 1 has been the oil of choice for many manufacturers as well as for lots of folks out there too. It is interesting to know though, that Subaru does not recommend the use of synthetic oil in the WRX! They do not object to it, but they do not recommend it either

 

Yea the subies are die hard Dyno oil... freaks...

in my subie I used Amsoil New Car forumula which is a Syn/Dyno blend until 5000miles where I switched to Amsoil 10w30.

I havent aten a DROP of oil in my EVO since my last oil change (1000miles ago). This is AWEASOME! I have been driving it pretty hard too. I think its sealed up and won't eat a drop the rest of its life (hopefully!) BTW - im still using Amsoil 10w30 in my evo...

 

well in the service manual it says:

Engine OIL

Fully synthetic engine oils displaying ILSAC GF-3 certification symbol ("Starburst" symbol) or conforming to the API classification SL or SL/CF

it also says that you can use SAE 20W-40 for temperatures 32F and above and SAE 10W-30 for -10F and above.

not sure where to get 20w-40 though.

 

Oil viscosities are determined at the molecular level. Are you telling me the engine clearances are on the factor of microns?

 

No you misunderstood.
The manufaturer of the engine determines what oil viscosity they will be using in the engine and then design based on that.

 

i thought we were supposed to use 5w30 in the evo's

 

well, 5w-30 is mostly used for very cold climate areas the majority of the time. However, I do not understand why the service manual and the users manual contradict one another. Correct me if I'm wrong, but dont heavier weight oils (mostly syn) hold up to heat better? Maybe its better to use heavier oils in the evo.

 

I agree. Even Ferrari uses 10W-60.

 

maybe ill switch to 10w60 when my warranty is expired!

 

While it's true that several degrees of viscosity can be safely used in most motors, it's good to remember that there are differences in the way engines are designed and built... Ferrari might use looser tolerances or clearances in some areas than uses in the EVO. Heavier oils can have negative effects because they do not flow as readily and could cause some parts of the engine to run without proper lubrication while the heavy oil flows through all the passages and clearances....
Just my $.02

 

daaaaaaaaaaaaaaaaaaaaaaaaaaaaamn

10w60 is expensive....

Cladius - I have not aten a drop of oil since my last change, about 700 miles ago. I think the amount of oil consumed was part of the normal breakin; hence Mitsu filling up the pans .5 quart over.

 

I'd stick to 10w30 as well...

A 10w60 is thicker, so even if nothing else goes wrong, you'd lose a few horses... If you didn't care for those few horses, I'd still be worried about flow characteristics when the engine is revving high. Can it get everywhere it needs to?

 

I dont think 10w60 is a heavier oil per say, its a multiblend and not just a solid 60 weight. Correct me if im wrong someone