Questions and Answers

Ford F-250, Gas In The Oil Q. Vince, I have a 1990 Ford F-250, 7.5 liter F.I. 4x4 with 95,000 miles. The heads and pretty much the rest of the top half of the engine (gaskets and seals) were replaced a little over 1,000 miles ago along with plugs, wires, cap, rotor, filters, PCV valve, etc.

Also, I replaced the entire exhaust system including manifolds and catalytic converter, not that has anything to do with my problem. The truck isn't driven that much, just quick trips to the dump and occasionally a short run on the highway (5 to 10 miles).

One problem is when the heads were replaced they were replaced with new, after market cast heads. The valve covers needed to be shaved down slightly to seat properly onto the aftermarket heads. The heads were cast for both center bolt valve covers or valve covers that bolt around the edge to cover a wider range of years.

One valve cover was shaved down a little too much so I have a very slight oil leak from the rear of the valve cover. I figure removing the valve cover and adding a nice bead of gasket seal along with another new valve cover gasket can easily fix that problem.

The real problem I am having is that my gas mileage has seemed to drop recently and the last time I checked the oil there was gas in the oil. I have also noticed as the engine heats up it runs louder (Valves tapping??). I'm thinking the gas is thinning the oil causing the louder valve noise. The big question is where is the gas coming from? Could the valves need re-adjusting since the heads are now broken in?

The anti-freeze also looks to have some oil in it, but it is not foamy, and the antifreeze is still green and not really sludged up, so I'm not sure if it is just residue kicked up after replacing the anti-freeze. (It was pretty dirty before I changed it) All my gauges are registering okay, the engine maintains a desirable temperature, and I checked the oil pressure with a gauge and everything checks out okay.

The truck never stalls, it starts right up (better when the engine is cold), but does have a slightly rough idle. I know I should check the fuel pressure to make sure it is not too high, and I don't think I have a mechanical fuel pump so I don't think that is where the gas is getting in. I would think if the new heads were no good or the new head gaskets have failed the truck would overheat or not stay running.

Do you think I'm headed in the right direction by suspecting the valves are out of adjustment or is there something else I should be considering? Any information would be greatly appreciated. Thank You, Ed

A. The only way fuel can get into the oil is through the cylinders. If you have a leaking injector(s), they will dribble fuel into the cylinders and from there get into the oil. A fuel pressure test will confirm or deny this; but I'm pretty sure you'll find out you do have some leaking injectors.

Let's worry about the valves after we get the oil dilution problem taken care of.