Hello:

A friend of mine has a 1988 Volvo 740 Turbo wagon.
He and his family have taken good care of the wagon.
The wagon only has 91,000 miles.

In the past two months the oil consumption has increased significantly.
I did minor diagnosis of the problem and cannot find any reason.

Below I list what I have done and I will be curious if anyone has other suggestions.

1.) I checked the air filter. It was old so I replaced with a new one.
2.) Checked the oil separator, flame trap, hoses. They are all OK.
3.) Checked engine compression. Strong compression (165 PSI).
4.) Check spark plugs for oil. No oil on them.
5.) Checked for oil blowby by opening the oil cap. No blowby.
6.) Checked the turbo big hoses. They are OK and not really oily.
7.) Checked the intake manifold. It is OK and not really oily.
8.) There is no black or blue smoke coming out of the exhaust even on accelaration.
9.) Checked for play on the front of the turbo. Small play but not really much.
10.) Checked the oil sending unit. It is not leaking oil
11.) Checked the distributor which is on the back of the engine. No oil leaks there.
12.) Air mass meter works OK.

So it seems the high oil consumption is not due to the Turbo.

That leaves the engine.

One possiblity could be the valve tem seals.
But given the low milage of the wagon, this would seem a likely cause.

Another possiblity could the the engine main bearings.
I am not sure about this possibility as I would think the engine would be noisy but the oil consumption would not be this high.

The rear main seal is not leaking oil. So it is not the rear main seal.

One clue which I cannot diagnose is that the oil turns grayish as if there is high carbon soot in the oil. The oil should be brownish or black.

I will appreciate any ideas as to what to do further in diagnosis this "mysterious" high oil consumption.

Juan Moran