Where the hell is my oil going???

[patrick66]

On my '66 Coronet 361 engine, my oil is vanishing. I'm finding no signs of leaks and no puddles. I drove the car a total of 555 miles over two Saturdays this past month. I did an oil change about two months ago - new Wix 51515 filter and five quarts of 10W-40 Castrol GTX. I've used both for many years without issue. The engine has about 70K miles on a 1983 overhaul. It runs beautifully, with no hiccups or hesitation. I can leave the car in my shop for weeks at a time, and it starts with two pumps of the pedal and maybe two revs of the crank.

I went to pull in my driveway last Sunday, and when I got slowed to about five mph, my oil light came on...****! It idled for a few seconds and the light went out. Since I was about 500 feet from the shop, I gently drove it up to the shop door. Light stayed out until I turned the car off.

I had maybe a quart in the sump! WTF, over?

With that, I'm not finding anything obvious as to where my oil is going! To have oil consumption at roughly 125 miles/quart is pretty mysterious. No smoke at all. There is no oil residue on the back of the car, and no oil under the car. There has always been a very small leak at the back of the pan at the corner, not the seal. I had a leaky driver-side valve cover leak I fixed with a new gasket a couple of months back. The loss of oil I'm speaking of is post-gasket replacement.

Fastest I drove was 85 mph or so, and the highest RPMs were right at 3300. The only thing I can think of is high crankcase pressure, which is blowing oil out somewhere. I've got another PCV valve I'll try and see at that point, what's up.

Any of you have any ideas?

 

[slimt]

Is the chassis wet?

 

[patrick66]

Not seeing any evidence of oil slinging, spraying, or coating the chassis. No oil residue out the exhaust or on the rear bumper.

 

[kiwigtx]

It has to be burning efficiently through the engine if there is no sign of leakage.

 

[patrick66]

The car runs beautifully.

 

[kiwigtx]

The car runs beautifully.

Not saying is doesn't.....my diesel work van consumes oil .....no leaks, no smoke....just uses it.
Runs like a Swiss watch.

 

[AR67GTX]

Long shot but I would try changing the pvc valve. In the late 60, just as my 64 Sport Fury was about to go out of 50k warranty it started using oil. Plymouth agreed to rebuild the motor and did so. Car still used oil so back it went. Picked it back up and they sheepishly said only thing wrong was a bad pvc valve. Problem solved. I remember having a lot of greasy oil film on the rear bumper by the exhaust pipes.

 

[beanhead]

Not saying is doesn't.....my diesel work van consumes oil .....no leaks, no smoke....just uses it.
Runs like a Swiss watch.

Roger, Roger. I had a 440 that did the same thing. Had none of the typical oil-burner symptoms, but would go through a quart in less than 100 miles...albeit that's still a lot less than the OP.

Patrick have you examined all your plugs? See if you can get a peek at the piston tops. And it may be as you say and blowing out your breather..though after a high-winder you can usually smell it somewhat. Good luck in your hunt...

 

[ruffcut]

I agree with PCV valve, but might be valve seals also, since the rebuild was so long ago. I would get a look at the spark plugs, and possibly piston tops if you can. It's getting used for sure.
Many years ago we had an olds that used oil like that and it took a complete rebuild to fix. ruffcut

 

[Hemi2Much]

Just out of curiosity have you checked your radiator to make sure it's not a blown head gasket in between the oil passage and coolant passage?

 

[BSB67]

The car runs beautifully.

That is immaterial. If its not leaking, it is burning from some source.

My Charger burned a quart every 100 miles or so. I took it to the track and it ran low 14s at 95 mph and weighed about 4400 lbs with the AC unit. I.e. it ran really well. Pulled the heads and had them rebuilt, then I got about 125 mi/quart. It needed rings.

 

[Darter6]

.no leaks, no smoke....just uses it.
Runs like a Swiss watch.

Same here with my PT Cruiser. Gotta check the oil every 250 to 500 miles.Usually 1 quart low.
My daughter had a PT too. Ran it out of oil twice. Kids don't listen.
Sometimes my 318 pickup will use a quart in 250 miles,sometimes it will go over 500 and still be full.
Maybe try a different oil ? Just a guess.

 

[dadsbee]

What valve covers? And is the PCV intake area shrouded?

 

[Lefty71]

Any of you have any ideas?

Super easy to look at the pistons for a little peek. Obviously easier to look at the plugs. Pull the PCV and look at the end. Antifreeze a nice green, or is it lookin brown?? Get pix of all of the above and repost here if you still are'nt sure.

 

[slimt]

Hopefully youll be able to solve the problem. Engines are not my thing. I can quick fix for a short distance. But thats all.

 

[Potts]

Either leaking.
Burning or
Mixing with coolant.

 

[Red63440]

Had the same thing happen to my 64 361 from the right bank and would use a quart every 100 miles. Oil on the rear bumper and rear edge of the trunk lid. The guy I got the car from told me he had changed the guides and valve seals about 21 years ago…mileage unknown. Engine had 61,600 miles on it and had some other problems like the car had not had any anti-freeze used in it for a very long time so the inside of it was really rusty and corroded. Anyway I got what I thought was a good deal on a low mileage freshened 70 383 with rebuilt heads and just changed the whole thing out. Haven’t had a chance to drive it yet but it runs and starts great.

 

[sam dupont]

One drip per second is a quart in 60 miles.

This is not a drip, but it gives an idea of how quickly a quart can disappear.

 

[tonysrt]

If burning oil it will show up at speed when you take your foot off the throttle because high vacuum sucks the oil into the intake. Maybe have someone follow you and take it out on the road at speed and let off gas pedal and see if that is your problem.

 

[patrick66]

Found no oily film on the rear bumper or decklid trim. Pulled two random plugs and found nice, dry plugs. The PCV looks ok, but I can swap the PCV from the Imperial to verify. The floor under the car is dry, with maybe two drops of oil under the back of the pan.

I'll start with the PCV swap and go to the "follow-me" visual verification of smoke/no-smoke. Before all this, I would have to add maybe a pint of oil over 3K miles. That, I can live with.