I just bought a 85 F250 with a 6.9 diesel.It supposed to use a quart of oil every time I fill up with fuel.Is this going to be a serious problem,or just keep checking the oil and deal with it.

 

Just an initial reaction, but I think you may be "overfueling" it. That is to say, giving it more fuel than it can use. With a gas engine you can "put your foot in it" and other than poor mileage it doesn't really matter. Not so with a diesel.

Way back when ... in my early 20's I was driving tandem axle dump trucks for a living. Most of the medium-duty trucks were gas engines (my favorite was a late 60's Chevy C70 tandem with a 427 V8/5 speed main/4 speed aux) and diesels were usually only used in truck tractors.

I went to work for a contractor who had a fleet of gas trucks and one diesel. When he found out I could run 5/4's he gave me the diesel. When I commented that it seemed to use a lot of oil he offered the "overfueling" comment. Said the excess unburned fuel was making it's way down into the oil and when it evaporated due to engine heat it took some of the engine oil with it.

Can't really explain the exact workings in detail but I found that after a little practice I could "feel the throttle", knowing just how far to push it, and only give the engine as much fuel as it needed to do the job. It almost feels like a strong resistance and with practice you find it hard to push past this "block".

I had 6.9's in both an '84 and an '85. I bet you occassionally (?) have a bit of a black cloud behind you also? Try backing off on the fuel ... easy does it. Pretend you're driving strictly for economy. I bet you oil consumption drops significantly.

Good Luck with it,
Roger

 

6.9s are known for using oil. does it leak? mine uses a quart every 500 miles or so, sometimes more. i just keep adding oil. and waiting for something to go wrong. 290000 miles and it's my daily driver.

 

Wasn't the 6.9 built by Intl Harvester.
I'm a little surprised they would be common oil burners.
Maybe its because of the high compression.

 

yes the 6.9 was built by IH. it can also be found in busses and med duty trucks.

one of the reasons they burn oil is the valve guide design, they tend to leak oil into the cylinders. they revised this for the 7.3 but it turns out the 7.3 has more valve problems because the 6.9 oil leakey guides stay lubed better.

the 6.9 is a tough engine with gear driven valve train and oil cooling jets under each piston. the weak points are the rocker arms and the injector pumps. also the earlier models had weak head gaskets. better head gaskets came out in later years, my '86 has the original gaskets (and everything else except the injection pump) at 290000 miles

good luck with your new truck.