My 83 F-150 is mysteriously losing/using oil. I've parked the truck on clean concrete, over newspapers, cardboard running the full length of the engine bay and I cannot for the life of me find where the oil is going.

I'm not seeing any smoke out the exhaust, but i'm still dropping oil at an appreciable rate. I'd say I'm using/losing a quart of oil every 100-200 miles. I've recently changed the pcv, added an oil breather filter, all my gaskets are fresh and installed correctly.

Anybody got any ideas?

 

None in the radiator/overflow?

 

Quart of oil every 200 miles has to go somewhere. If it's not leaking, has to be going out the tailpipe. That much oil should have shown up pretty evident in the cooling system. I'd run a compression check, leakdown test if possible. If it smokes on startup, then clears, valve seals. You would be surprised how much you can burn that way. Pull the plugs and look at them. That will give you some indication of what the engine is doing.

 

I had originally replaced the head/headgasket a while back because I was getting some oil into the radiator. Since I've replaced the head and gasket I haven't noticed any oil in the radiator. I'm not getting any smoke on start up, or any other time.

I haven't pulled the plugs, but I'm not detecting a misfire or anything else while the engine is running.

Compression check is forthcoming, leakdown may have to wait awhile.

 

While I love my all tools and gadgets, people were diagnosing engine problems for a long time before modern equipment by reading the plugs. When one or two shows diff than the rest, it means there is a problem with that cylinder. As you said, the oil is going somewhere and it doesn' just evaporate.

 

leak down test-

don't know what that is but a mechanic buddy has a vacuum tester type thing he puts on the radiator to test THAT system. Wonder if the head/gasket wrk you had was tested to see if it was done properly? Did you have the oil loss problem before the head wrk? Also:
I second gfw1985 idea. Check each plug let us know what U C. Look for wide differences in each plug or to see if there is any black sooty or wet oilly resude.

 

I had the oil loss issue before I ever replaced the head and gasket. I've had the cooling system pressure tested and I'm its holding pressure so its not leaking there.

I'll be pulling the plugs shortly, right now the truck is being used so I can't pull the plugs out at the moment. I've kept a good eye on the dipstick, and so far I haven't lost any oil since I originally posted this a couple days ago.


Maybe this weekend I can get the plugs out and post up what I find.

 

Could be leaking out on to the exhaust and burning and not hitting the ground. That is what my truck is doing. Couldn't tell by looking at first either. Had to crawl under and look to see. Can you smell burning oil around the truck.

 

oil loss issue before I ever replaced the head and gasket... so far I haven't lost any oil since I originally posted ...
How many mi was it loosing a qt every couppla hun. mi? May B has something to do w/the head break-in...no that would B the opposite...mmm, Oh it was B 4 the head wrk...hmm, got me 8-0 .

 

I can't smell any oil burning. Only scent that the truck really gives off is the normal "warm exhaust" smell for when shes in tune how she aughta be.

I was losing MASSIVE amounts of oil before the head and gasket change out, but now it seems to have calmed down a bit. Hopefully it was just everything on the head breaking in and it'll go down to no consumption or very little.

I'm still checking the plugs, and planning on running a compression test this weekend to see where I'm at. I do know other than the mysterious oil issue, i'm getting right at 20mpg, and the engine pulls a solid 22" of vacuum at idle.

 

Worn valve guides are notorious for mystery oil loss. SBCs are known for the blue salute on start up but don't seem to burn too much. My much abused 92 Ford work truck showed almost no smoke but burned a quart every 200 miles. Four spark plugs would become bridged with carbon and oil about every six months. A vacuum gauge helped to pinpoint the valve guides as the culprit.
Another area to check is the PCV system. Make sure the right PCV valve is installed and the hoses are in good shape. I had one engine that started burning oil because the baffle inside the valve cover had broke off.
regards
rikard