[vtirocz]

Originally Posted by DorkMissile

My pictures and comments are relating to conversation earlier in the thread. The issue is that people are trying to force 10qts in after their oil changes, but the system capacity is only 10qts. There is no way to get all 10qts out when doing a change. So they drain out 9, pour in 10, and call it a day. My point was to show what 10qts looked like in a bone dry engine.

The issue with these engines is that they are known for having large amounts of oil digestion issues. We are talking about puddles of oil in the intake.

The problem with that is, being these are direct injected engines, there is no fuel being delivered prior to the valves. When you combine really hot valves to oil vapor, you end up with large amounts of deposits on the valves. Its like layer upon layer of burnt on molasses on the stems of the valves. And there is no fuel being sprayed on the valves to cool them and wash them. You can search on the forums here and find plenty of bad images of really gummed up intakes, heads and valves.

The problem with running the oil to the top of the hash marks is that given there is no extra room in the engine for the oil, it ends getting churned up by the crank and rods, which creates massive amounts of oil vapor that the PCV system cannot deal with. The other thing is that this churning effect turns the oil into a well emulsified mixture of oil and air being pumped thru the engine, which can create major issues with things like the DOD system and bearings (air can't support things like the crank when under pressure between the journals & bearings)

I myself run my oil down under the hash marks. When doing so, the amount of oil I was seeing in my catch can went down 95%

You have me curious now with your feedback on low oil level (below hashmark) showing favorable trends in catch can trapped oil. That's an interesting datapoint that I don't think I've heard of yet. In fact, I've never heard of people intentionally filling to below the hashmarks or OEMs recommending that, especially for engines in performance applications.

I do have some questions:

• 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.