Quote:
Originally Posted by MRV99
From what I know about engines(heavily modded early 90's and only USA blocks) short run times and not really getting the engine up to temp tended to burn oil. I could run 500 miles on/off over 2 months in town and burn oil yet run 1500 miles (100 at a time) over 15-20 days and not lose a drop.
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I agree. What do the S65 motors typically run for oil temp? That would be my first question.
60W is incrediably thick. I don't know of anyone that specs that kind of weight for their consumer powertrains except BMW .
To clarify what I'm thinking is occuring (assuming I'm right about the oil temps) is that the S65 isn't reaching 100C on the oil. TWS is acutally a fairly light 60W with a 22.7 Cst (the range SAE spec's for a 60W is 21.9 to 26.09), but It wouldn't surprise me to learn that it's simply not reaching 212F in temp for normal driving, as most of the N/A engines I've had like to turn between 150-180 or so. if it's running something closer to that, then you're basicly paying $14/bottle for a 60W that only ever acts as a 40W (TWS @ 40C has 160 mm2/s which is that of a 40W oil) .
A F/I engine would have no problem reaching this, you'd see 200-225 all day long, but unless the S65 runs a pretty high t-stat, I'm thinking it's simply not reaching it's nominal viscosity, and if it's not then all the bearing and ring tolerances are not in spec, and then you'll have excessive blow-by.
I believe BMW initally recognized this with the E39 m5 when they spec'd M1 5W30 for a time, simply because you don't drive these car's hard enough to warrant a 60W. The problem there was that they didn't readjust the ring tolerances to run a 30W oil-- they acutally TSB'd new rings to try to solve the problem but eventually they simply went back to a bandaid fix and spec'd the 60W in thinking that some customers would acutally reach the temp and others would just have to make due.
What you get when you have a high RPM oil consumption situation is typically crankcase blow-by and that's different in that it's a function of high crankcase pressures causing blow-by.
This is simply a function of the oil not being hot enough to close the tolerances to their nominal spec.