kael

Been chasing an oil use problem in my '87 mostly stock for the last year or heck, for the two years I've owned her!

Since tracking, losing a quart in about 800 miles. I've walked and crawled through a lot of things to address this. Valve seals, valves, heads machined.

What I'm wondering, in this thread, is if it's really normal.
I'm not racing, but I do like to get on the gas a bit. Not WOT, but a lot of heavy take off from lights, getting on the Interstates rather quickly, etc. Like many C4 drivers.

Thoughts? Is my heavy foot burning a bit of oil?

Whaleman

I am sure experts will chime in but I would be concerned with a quart every 800 miles. While I don't drive real hard I am 3800 miles into a oil change and I have had to add nothing. Dan

Pwnage1337

Does car smoke when you start it up? (Leaking valve seals)

I'd check PCV system, also the intake manifold seal. I had an intake not seal and under heavy throttle would pull oil from the lifter valley into the intake runner. It burned through oil very quickly

Benny42

How many miles are on it? What condition were the cylinder bores in when you pulled the heads? Does the car have cats? This info will help diagnose it.

billschroeder5842

Whaleman is on target. 800 miles is a oil hemorrhage. You have something way bigger going on.

You need to pop each plug and check condition. You need to isolate this soon. I'm not sure that tracking your car did any damage but the track maybe exacerbated an already existing situation.

jv9999

800 miles is on the hairy edge of OK. Most manufacturers won't warranty repair any consumption issues less an a qt/1K or so. For Nissan and their infamous 3.5 a few years ago it was 900 miles (nice engine with poor oil control).
As others suggested, check the plugs and see if one or more are oily. See if you have excessive blow-by pressurizing the block. Change the PCV valve. Pull the dipstick and see if you have vacuum or pressure. If all looks OK, I'd relax and buy the oil. It's cheaper than an engine. Maybe switch to a heavier weight oil if you live in a warm climate. I run Castrol 10W-40 in mine, but it sleeps in the winter.

81c3

Bottom line is, if its not visibly leaking, its being burnt in one way or another.

My guess is poor oil control in the cylinders. Its probably not enough to show smoke out of the exhaust where you can see it from the driver seat.... but I would bet it is going out of the tailpipes. Have you had someone watch as you take off?

Another thought is it could be leaking off the back of the engine and burning off but not causing a visible leak. Maybe off the exhaust itself.

Another thought is, if its a stick, it could be leaking out of the rear seal and making its way onto the clutch disc and burning off that way as well...

Maybe a combination of several different issues....

mtwoolford

Going coast to coast and using four quarts of oil would be an "oil hemorrhage"?

Granted, newer, tighter engine can and do use less oil, but lets keep things in perspective and not become alarmists; its a thirty year old car with what may very well be the original engine. The next time the spark plugs get pulled, look for signs of oil fouling...that would indicate a problem.

All engines use some oil, any engine that never uses oil, has a fuel dilution or other problem going on.

kael

Thanks for the opinions, it all comes down to the last thing I want, #2 has worn rings. I've been putting off a leakdown test, but pretty sure what it will show.

My amateur mechanic experience is 2 years, with my '87, getting the heads machined/refurbished/whatever was the first time I dove into an engine, well a full sized engine. So, I was hopeful some other problem might explain the oil usage with no drips, no smoke that I could see or smell. And a good running engine, as far as I know. Not like I've driven another C4.

I'm not in a position to service this, skill, space or $$$ at this time. What's the opinion of smoke stopper or similar as a patch for the next year?

ddahlgren

There is no such thing as rings in a can or bottle. You might try some 20-50 conventional iol rather than 5-30 synthetic.

mtwoolford

now you tell me

Rings however can carbon up and get sticky or stuck in the piston ring lands; in the bad old days, all the spark plugs would get pulled, the cylinders would be soaked with a penetrating oil such as Marvel Mystery Oil and allowed to soak, hopefully freeing up any stuck rings.

kael

I already went from 5-30 to 10-30. I know there's no rings in a can that lasts forever, I'm hoping for a year/6k.

Time to roll the dice.

Churchkey

This ^^^^^^^^^^^

Suggest Rotella - T 15-40.

Have someone start the engine & watch the exhaust if blue smoke on start up it needs valve stem seals replace with the umbrella type.

More often than not bedding the rings will help. Don't have time to explain the procedure check Google.

QCVette

Do you see any smoke?

At start up or deceleration it is valve seals/guides. Under acceleration load it is usually rings.

How old is the oil and what brand?

I had one car that was built "loose" with more clearance in fitting the pistons, bearings, etc. It ran great, but the oil consumption after an oil change was about 1500 miles to the first quart, then about 1000 miles to the second quart, and about 800 miles to the third quart. Then oil change and start over. That was with Pennzoil yellow bottle conventional oil. I switched to Castrol GTX and it improved to about 2000 miles for the first quart and an oil change before the second quart.

I also had a Pontiac 421 SD that GM stated would use oil. If it made it to 1000 miles without adding oil, that was very good.

Those are unusual situations/engines though. Our Corvettes are not supposed to use that much oil. Something is wrong. Give us some more information on when or if it has any smoke. Try changing to another brand of oil. Try checking plugs and doing a compression test/leakdown test. It sounds like you have already checked a bunch of things though. If you are lucky it may be something minor like a stuck PCV or something, but until you check it out further it is hard to tell.

Good luck.

81c3

Here, let me repost my post.... others are asking the same questions I did...

Bottom line is, if its not visibly leaking, its being burnt in one way or another.

My guess is poor oil control in the cylinders. Its probably not enough to show smoke out of the exhaust where you can see it from the driver seat.... but I would bet it is going out of the tailpipes. Have you had someone watch as you take off?

Another thought is it could be leaking off the back of the engine and burning off but not causing a visible leak. Maybe off the exhaust itself.

Another thought is, if its a stick, it could be leaking out of the rear seal and making its way onto the clutch disc and burning off that way as well...

Maybe a combination of several different issues....


In addition, I would stop the "heavy take off from lights" until you figure things out. How many rounds on the engine anyway? If I read your post correctly, you've already had a valve job and seals done right? You tracked the car how many times?... So, a new valve job, new seals... everything is tight up top... My guess is maybe now that the top end is tight, the oil is being pushed out of the exhaust ports a little more and burning...

Tom400CFI

YES....using 4 qts on a coast to coast drive is quite unacceptable.
The number of years on the engine has nothing to do with oil consumption. Nor should the miles....if it's been cared for. To wit;
My 'Vette has about 180 k...it's "25 YEARS OLD"...yet it doesn't burn a qt in an whole oil change which is about 7k miles.

Wife's LS6 in her 'V has 150k, I just changed the oil in that @ ~7k and it had lost less than a qt.

Finally, my old '96 Silverado has been HAMMERED, towing my boat through the rocky mountains for 296,000 miles....and guess what? It barely burns a qt in it's change interval which is about 5k miles.


Then OP has a problem that is unacceptable. He should be alarmed and he should be investigating the root cause. And the root cause is NOT "30 years old".


.

gerardvg

Hi

Is the 87 meant to be using 5w30 oil? try regular 20w40.
My 85 engine got replaced a few years ago with 170,000 miles on the clock, it did not have to top up oil between oil changes and have a heavy right foot. Just wanted a new engine for more performance.

Are you using standard valve covers? they have baffles to prevent oil getting picked up by the PCV valve.

can only be loosing oil via leak or ingestion via excessive blowby from broken rings / ring landings..

mtwoolford

I'm happy for you, but, alas, "results may vary"

for instance, my friend was concerned that his late model Cadillac used a quart of oil every 1,000 miles; "that's normal" says the Cadillac dealer...

I'm going to make the assumption that your vehicles have received excellent maintenance to post such impressive numbers, but again, not all vehicles receive the same level of care...and speaking only for myself, a thirty year old car that used a quart of oil every 800 miles would not be cause to become "alarmed"...as long as I kept checking the oil of course.

Whaleman

I sure do not know. 32oz (quart) every 800 miles is 8oz per 200 miles or 1 oz of oil every 25 miles. Seems like a lot. Dan

81c3

Ive had more than 80 cars/trucks in my lifetime so far.... I remember only 1 having a very bad oil consumption issue... my Jeep Scrambler. It used a quart + in about 1000 miles... It had a 4 cylinder IIRC... don't recall the mileage.
What I do know is that the engine needed an overhaul. I traded it in at a Ford dealership and the owner, who I know, kept it as one of his own had the engine rebuilt...
Ive had other vehicles that had 200k mile + and never needd a drop between changes... I say that a quart in 800 miles is a consumption problem and not normal.