I have a 1989 F250 7.5L V8 with 89,000 miles used for work only. For the past couple of years I have been putting roughly 3 qts. of oil every 1,000 miles.

Just got it back from the dealer and they couldn't find any evidence of a leak. Everything was dry underneath. The service guy said it was because of the age and not the mileage that it was using the oil. That doesn't make sense to me.There is no sign at all of any smoke at the exhaust of under the hood at anytime (warm-up or driving).

Where's the oil going or why?

 

Look for any exhaust smoke on startups. You may have bad valve seals.

 

If it's not leaking it it is burning it one way or the other. Try smelling the exhaust and see if it smells like burning oil, although 3 qts every thousand miles should be smoking.

 

As I said in my post, I don't see any smoke what so ever at the exhaust. I've had someone start the engine while I'm at the exhaust and no sign of smoke. Driving me nuts.

 

3 qts every 1000 may not be smoking, especially if you have the factory cats catching oil.

Time for blowby, compression, and leak down tests. Performing leak down ring test on each cylinder is tedious, you have to find tdc on comp stroke on each one.

 

Didn't see anyone mention the PCV valve.

If it's not Motorcraft, then I call it junk. It may be as simple as a malfunctioning PCV valve. Either a cheap one allowing oil to be sucked in or an old one sticking and allowing for oil to be sucked into the intake.

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I second checking the pcv valve - motorcraft only. I am not familiar with the 460, but on my 302 there is an air tube that runs from the oil filler neck to the airbox, and inside the airbox there is a small filter. I would check that too to see how dirty it it.

 

Good suggestion Timbersteel & BLDTruth. I'll check it out.

Thanks

 

Oil smoke comes out of a cat nice and blue, fwiw.....(our luxobarge started smoking on startup, and it's not even 18 yet!)

Rev it up to 2000 rpm for a few minutes and see if you get a puddle. For best results, do this on a new concrete or paver driveway.

 

I saw something similar on a TV show,

it was a corvette and it was 'burning oil' so the owner thought,

they torn the engine apart, and found that the intake was full of oil,

cant remember how they fixed it.

 

This sounds like clogged pcv. The engine will eat oil vapor from a clogged pcv no problem, without any real symptoms, but when it goes unaddressed long enough...oil collects in the intake, and puddles collect even more vapors, creating a chain reaction which turns into an oily mess. The engine can't digest oil in liquid form the same it does vapors, so now it blows blue.

 

I put in a new PCV valve and the problem is still there. Does anyone have any other suggestions?

 

Back to the advice in Post# 5: https://www.ford-trucks.com/forums/1...l#post16681772

 

When you replaced the PVC valve, did you check the vacuum on the line going to it to be sure there was vacuum getting to the valve?

 

I saw that too...intake manifold was wrong. The mating surfaces were cut at the wrong angles, and the gasket could not make a seal at the bottom in the valley...it was off by almost .125 at the bottom. A proper intake manifold and new gasket was the fix.