There are also many M3 owners running a 75w140. The difference is not really noticeable. Maybe a thinner oil would net you a couple horsepower too huh?

how would differential/gear oil gain you hp?

Just going by the logic above in a sarcastic way. If thicker gear oil would make you slower than surely a thinner gear oil would make you faster.

^^^ but being faster doesnt always mean "gaining hp"

it could possibly help reduce parasitic loss (negligible though I think)... but hp is derived from engine... I understand what you are saying though (now)

Actually if you were measuring hp/torque on a dyno, he would be correct. It takes xx hp to overcome the friction in the engine/tranny/drivetrain. Any reduction of friction would show up as a hp increase on the dyno. Since the majority of hp/torque measurements here are done on a dyno, this is what I assumed he meant. He should clarify though

Yeah, it was what I meant. It's been a long day

I liked the ninja edit

its not adding hp though, its lessening hp loss at the wheels - you know as well as I do you can only add hp at the engine.

and in any case gear oil isnt likely to make a notable difference in most situations

^^ That was my original point and why I started to say it was a bad analogy. It is hardly noticeable at least to me.

^^^ its understood now... but somehow Jeff and I will find a way to act like we dont understand each other

LOL... I have noticed that in several threads.

The main reason I went with the 75w140 was for the added protection. I do track my car from time to time and have also done some drifting on a wet skid pad. Given the additional abuse I put it through I wanted some more protection.

a finned cover and/or cooler would be good insurance.

Yes. I have considered these

I dunno Mike. Is gaining a few hp via using a slicker engine oil count as "at the engine"? If no, then cool.

Then yes, then I don't see how using a slicker gear/diff oil can't do the same.

But of course I knew what you meant. I was being technical like you Mike.

zack (RareJDM) has a very nice kit... dunno if/when they will come out with it (as product for sale), but if you are seriously considering it you might want to hit him up ~