Quote:
Originally Posted by vtirocz
- You mentioned these engines have large amounts of oil digestion issues. I understand what you're talking about, but is there actual evidence of performance degradation due to this? I'm not looking to argue, I'm genuinely interested if there's performance degradation that's associated with this.
- Why would GM specify to fill the oil to the top of the hashmark, particularly for performance driving, if this is harmful? That just doesn't make sense to me. It would be cheaper for them to factory fill 1 quart less and also pay for 1 less quart for the 2 free oil changes.
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All I can do it break it down how I see it:
Q1 - The two things that concern me about the oil digestion issue is (1 to a lower extent) how bad these engines build up layers of burnt oil on the valve stems and (2) Detonation issues relating to oil vapor. Oil vapor can cause pre-ignition / detonation which this engine has problems with already (ring lands)
Q2 - The engine development process happens YEARS in advance of that of the chassis that the engine will go into, so they don't see all issues until both come together. At that point, it is too late to do anything internal to the engine, so out come the band aids. The factory PCV system went thru three revisions in the Corvette, and really was never solved. Want proof? Look at how much effort that GM has put into the PCV system on the LT2 to address these issues. They specifically say that they added a separate direct feed oil pump to force lubrication to the top end / cam vs letting it drain back due to oil draining onto the crankshaft.
My best friend works at GM at the Prooving Grounds - he specifically told me when I was buying my Camaro the small little catch can box on the intake was the thing that got the oil consumption under control enough for it to pass emission testing. It did noting for the owner once it was full, but it took a few thousand miles to fill up.
I have had several want to take on this debate, and that is ok with me, but I have yet to head anyone tell me what will happen if you ran the oil 1/2 to 1qt low.
Ive done it, under more boost that you are supposed to run on a LT1, on E85, with Meth Injection, on a stock bottom end while making more power that you are supposed to and took the engine apart and inspected everything myself. All bearings and cylinder walls looked perfect considering I ran it under the hash marks the entire time.