23 MPG, what????!?!?

[RG5384]

does 23mpg on the interstate going around 80 from atlanta to mid florida sound even close to what i should be getting??? the car is an 83 300SD. I thought they should get closer to high 20's or even 30?. thanks
R

[psfred]

Ryan:

27-28 would be more what I expect. Check for a fuel leak, especially on the injector return lines -- they are fragile and leak if disturbed too much. The fuel evaporates off the engine, so you won't see it dripping.

Look for leaks on the steel lines under the car, also -- I have heard of at least one instance where someone sold an SDL about the age of yours due to the wife tossing fits about puddles in the drive -- turns out the steel line under the rear seat was rubbed through and leaking.

Make sure your rear brakes aren't dragging, too -- if the car "jerks" to a stop under light pedal, the pads are dragging. You won't notice anything else if the rears are dragging -- fronts usually make the car drive funny.

Peter

[RG5384]

thanks, i don't think it's the rear brakes or the steel braided lines as the only thing it leaks is oil. I will check the return injector lines, and hopefully that's it. I didn't notice any unusual smells though, when parked or running. thanks, any other things to check? the valves were done about 4k ago, so i think they are ok.
Ryan

[RG5384]

i just checked the return lines. they are the white(used to be white anyway) braided lines that come off of the injectors right? i did not smell anything on my finger after i ran it across them, and they didn't feel wet at all. My inline fuel filter didn't look too happy though, but that would harm my mileage would it? it would just not alow the car to run as high rpm's right? Also, i have noticed a strange vibration when running through 900 rpm. I can't duplicate it by holding it at 900rpm, only when it passes through. It didn't use to do that, as i would have noticed it before. Could these two problems be at all related to each other? thanks
Ryan

[psfred]

Ryan:

Dirty filters can give running problems, but usually don't decrease milage all that much, just power.

Change your fuel brand, diesel fuel isn't as consistant a product as gasoline is. I have found the local Phillips 66 to be horrible -- lots of smoke, no power, lousy milage -- while the local discount dealer is fine, as it Shell or Amoco/BP. It is entirely possible that the fuel you used gave you much less milage than normal, especially if you had more smoke!

Peter

[RG5384]

thanks, i suspect that the fuel may be the problem, as the last station that i filled up didn't seem to have much diesel business(pump was dirty and uncared for, on side of building, no overhang etc). Is there any additive i can keep in the car during long trips to help mileage from bad diesel?? thanks
R

[psfred]

Ryan:

RedLine is my personal preference, but any typical "truck stop" additive will help.

Speaking of truck stops, that is where I buy diesel when on the road in unfamiliar places. It can be an experience (the pumps are in pairs and you sometimes will have to ask which one to use -- makes one look stupid, but better to ask than hold up the show!). You will always get good fuel, they will have diesel oils and additives if you need them, and will have winterized fuel when the temp drops dramatically. Much safer than whatever is in the tank at a dismal station in nowhere!

Peter

[RG5384]

thanks, for the majority of the trip we did jsut that. It's only when we got around the valdosta area that we stopped to eat at a wendy's, and it was the only diesel station at that stop. I brought along some injector cleaner cetane boost stuff and used it all up on the trip to atlanta, our mileage to atlanta was calculated to be around 25-27, with some in-town use. Perhaps that additive stuff is really worth it. Thanks again, hopefully i wont' have to post about this topic again! thanks peter,
Ryan