Join Date: Aug 2008
Location: Topeka, KS, USA
Re: Mysterious oil loss
If it's truly burning oil in the combustion chambers, it can come from several sources. 1: Excessive blow-by into the crankcase. This causes the oily residue you see in the intake. Some oily residue in the intake is normal. On cars, a stuck PCV valve will cause high oil consumption. Your LT does not have a PCV valve, only the vent line referred to in earlier posts. It is unlikely this is the issue. 2: Bad piston rings. This will cause #1. It builds excessive pressure in the crankcase and it blows through the PCV line, carrying oil mist with it, which then burns off in the combustion chamber. Also unlikely at 86,000 miles, but possible. 3: Bad valve seals. On overhead cam/overhead valve engines the valve seals will allow oil directly into the combustion chamber when they get weak. This is where I would look, particularly if you have run synthetic oils or additives in your oils.
Do a compression check. The pressure is not as important as the consistency. If the chambers are all within ten pounds or so of each other, your rings should be ok.
Changing filters will not stop the oil you see in the intakes. It's normal, but can be where the oil is being lost if your rings are bad. Bad valve seals will have no obvious symptoms other than sometimes causing excessive smoke on start-up. Bottom line is that modern engines can burn quite a bit of oil before they will smoke out the exhaust from it. The catalytic converters just burn up the smoke before we can see it.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Last edited by deanwoolsey; Aug 12th, 2014 at 3:34 pm.