1992 G30 Oil consumption

I recently purchased a 1992 Chevy G30 with the 5.7 and 700R4 trans. 122,000 miles on it. Runs smooth and quiet. Complete maintenance records came with it.

My problem is oil burning during/after idling. When accelerating from a traffic light it will have a small puff of blue out the tailpipe. If it idles for 5-10 minutes it will be a large cloud when you accelerate. No clouds during deceleration so the valve guide seals should be fine. No clouds when starting it cold either.

The air cleaner is clean with no oil present. PCV valve is new. The old one that I removed was still good. Oil level is fine and is 10W30 weight. I tried to check the timing but can’t see the timing marks and don’t know how I would get my timing light close enough. I thought that if the timing were late, the vacuum would be too high.

Any other thoughts appreciated.

How much oil in 1K miles is it using?

I can't answer that yet. I've only put 150 miles on it since I bought it.

I can't answer that yet. I've only put 150 miles on it since I bought it.

I would change the oil and get some miles on it and see what it does.
You might want to pull valve covers and see if drain back holes are stopped up.

Since I've changed the oil & filter I see that it has used one quart in roughly 1000 miles. There is a small puff of oil on startup. Most clouds occur on acceleration from a traffic light.

This is looking like valve guide seals. The vehicle was used regularly until three years ago when it was demoted to "spare" status. The seals must have dried up while sitting.

I would just give it some more driving.
Change it or Add another qt if it goes down another qt between 1-2 thousand and then change it again
Good clean oil and a couple of good changes and driving it may help.
You might check pcv valve and vent system.
Good Luck

The PCV valve is new. Vent system is working fine with no obstructions.

This van is a 12 passenger model and was used regularly until 3-4 years ago as a school bus. It then sat around as a spare vehicle until April when I bought it. This is probably why the valve guide seals dried up.

The clouds of smoke on acceleration are not something that I can ignore. They choke out anyone next to me in a convertible. It also smells to drive it when I have my windows open. I've been slipping it into neutral at long lights and keeping the RPM's up to avoid oil clouds when needed.

I'll change the oil & filter again at 2000 miles.

You might pull the valve covers and have a look in there.
check drain back holes and see if any valves have any sideways play.
Stoped drain back holes or lose valve guides will give it a smoke.
Or even leaking intake gaskets.
Good Luck
MT

OP,
Consider the possibility you might have balky oil control rings from all the time the van was off the road. Often that will resolve itself with regular oil changes. Another method to free them up is to put it in second gear and wind it up to about 40 mph then coast back down to zero. Repeat a couple of times. You also might try using motor oil designed for high mileage vehicles.
FWIW
YMMV

I will remove the valve covers and check things soon.

When I bought the van I changed the oil and filter right away. I used a high mileage oil and also put in a quart of Rislone to help clean out any junk. To date I have about 2000 miles on it since the oil change and will change it again in the next few days.

Rislone or cleaner is not a good idea.
Pull valve covers and see how things look in there.

The engine gunk and sludge may be in the drain back holes.
Good luck
MT