My 86 6.2 using oil, not sure where. Please assist!

[wreckmaster]

Hi everyone, i have looked at other oil consumption threads but i cant really compare mine to others because of some variables. So i am going to point out as much details as i can, so if anyone has an idea on what it could be it can make it easier and quicker.

I got a 1986 6.2 with 87,900 miles, that had been sitting 5 years before i bought it from the guy. I have driven it for a few months with hardly any problems and not to much noticeable oil usage. Than recently i installed an ATS turbo kit that i had picked up with another 6.2. Turbo and truck both ran great after we got it installed.

For oil i had been using Rotella t 5W 40 because well it was winter. Than i just recently switched to Delo 400 15W 40.

In 276 miles the dipstick read from 1/8 inch below full mark, to it requiring a half quart. Those 276 miles have mostly been interstate/highway. I do not see any oil puddles on the ground, nor any oil spatter on the tail gate. I checked the CDR valve and it has negative pressure (oil gets sucked into tube).

The turbo seals seem to be OK because i see no oil on the outside of the turbo, and i recently had the turbo off to redo the oil drain outlet(which was my first thought of oil getting used, because it wasn't draining properly, which could of have been putting pressure on the turbo seals). With the compressor housing off there was no noticeable oil running down from behind the compressor wheel. The turbo doesnt appear to be burning oil either because the color of the smoke isn't the typical color that indicates its using oil.

My thought is the felpro valve cover gasket we recently put on is leaking, but wouldn't there be an oil puddle on the ground or a tell tale sign of a leak? I do have a few oil droplets hanging from the drive shaft and starter, but that is where they stop.

I do get residue smoke out of the oil fill cap, so could it be my compression is crappy and I'm getting too much blow by?? Even though the truck appears to run fine.

Hopefully i somewhat narrowed the problem source down enough.

Thanks.

[DmaxMaverick]

Unless you can account for an actual, visually confirmed leak, or oil-smoke exhaust, 1/8" on the dipstick is nothing to cause concern. The level can vary 1/8" or more from check to check for no reason at all, even when all the conditions are the same. Unless it's 1/8" less every time, at similar miles, it's probably nothing. They will use some oil, normally. The most common cause is a plugged air filter (or critters taking up residence in the intake). The least common cause is the CDR. The addition of a turbo will increase oil usage, due to the increased air demand on the intake plumbing, and the volume increase of the air in general. If it's able to maintain about 6-7 qts. between changes, it's fine. Don't sweat that top quart.

The valve covers should be sealed with sealer, not gaskets. Unless you have a specific need to remove them often, gaskets are useless, and will almost always leak. "The Right Stuff" sealer is the preferred product, but I've used RTV blue and black with success (red with less success...depending on what I had in hand and the urgency of the job). None of the "sensor friendly" RTV's have worked well for me. Just as important is the condition of the covers. They need to be true, with no dents on the sealing surface, especially the bolt holes. It's best to "finger tighten" them with fresh sealer, then 1/2 torque as soon as the sealer begins to cure (so it adheres, but doesn't ooze out), then fully torque when near completely cured (not after fully cured). Times depend on temperature and other climate conditions, so it's a good idea to put a good glob or two nearby and test it occasionally.

[wreckmaster]

Thank you for the information maverick. I checked the dipstick again before refilling it back up to full, and it was border line to the add 1 quart mark. I understand the turbo will put more stress on the oil usage, but using nearly a quart in about 300 miles was my concern. But ill do some more tests and checks. Than see where it stands again.

I want to be able to enjoy my daily driver, instead of worrying about the poor thing all the time. ): But i guess that comes with having a 24 year old truck. :)

Forgot to mention in there that we replaced the filter too, whoops. I plan on putting RTV on the valve cover too here eventually. Didnt realize until after we had everything put back on that those felpros were no good.

and again thank you, you have been very helpful

[DmaxMaverick]

Probably nothing spectacular, then. If it sat for 5 years, the rings are probably sooted in place. Valve stem seals are probably hardened up, too. They will loosen up with some running, or you can speed it along with oil additive, like MMO (don't use ATF). Given time, current oil formulations will break it up (and soften the seals). Hurrying it along can, in some cases, cause chunks of the stuff to break off in large(r) pieces, while the oil additive package will remove it in much smaller/safer particles.

One quart in 300 miles is a lot, for any condition. However, it's only oil, and completely harmless to your "oil burner" (no plugs or cat to foul). After sitting so long, I suggest just running it and watching the oil consumption. If it doesn't start to decrease between the next couple oil change intervals, perhaps then look a little deeper. Get some miles on it and cycle the temperature a bit (alternate hard to easy runs). The extra pressure will free up stuck rings, and the temperature cycles with new oil will revive old rubber seals and flush particulates to the filter where they belong.

[JohnC]

If you want to look for issues, I'd start by checking the crankcase vacuum while the turbo is cranking out boost. This would require you to plumb a vacuum gauge into the crankcase somewhere. Through a spare oil fill cap would work. Normal crankcase vacuum is measured in inches of water. One inch of mercury (what your vacuum gauge will read) is roughly equal to a foot of water, so any significant reading in a mercury gauge is probably too much.

Another thing to check is the turbo lube oil return line. Any restrictions, kinks, etc there will force copious amounts of oil past the turbo seals and into the intake. On a Diesel this could be a real problem...

Otherwise, if it sat for years, the oil rings could be stuck, but I would have expected that to rear it's head right away.