FL 70

[TXDave]

I have a 98 FL 70 with a 5.9 cummins and a auto trans ...what should my MPG be ? I am getting 6 mpg now but that seems low ? :-(

 

[Weave]

That does sound low, even with an automatic. My old truck had the 5.9 with 6 speed manual, and it got 10.5-11 MPG. Have you had the engine's valves adjusted recently? If not, this might help improve the MPG, especially with Cummins 5.9's. With the automatic, the 5.9 should get at least 8-9 MPG.
-Weave-

 

[RichM]

Do you do a lot of idle a lot. You get 0 MPG when you idle.My FL 70 with a Cummins 8.3 C gets between 10-12 MPG based on the load and winds. Strong wind conditions really put the mileage in the toilet.I cruise at 2100 RPM and at that rpm am doing 65 mph.

 

[TXDave]

well I just bought it and I drive 460 miles per day ...I spend $ 110 a day in fuel at $ 1.65 per gallon ....I have not had valves adjusted and it now sems like it is running to rich ....its only got 175000 miles

 

[Weave]

I would bring this truck to a Cummins shop, and have them adjust the valves and check the injection pump timing- basically a diesel engine "tune up." On the easy end make sure the air filter isn't dirty if you haven't checked it yet.
-Weave-

 

[TXDave]

If I put it in nuetral and floor it ...it pumps out blue exhaust and runs rough ! but driving it you cant tell anything is wrong ?

 

[Weave]

Definitely something wrong with the fuel system that you might want to address real soon. It might have a few bad or weak injectors causing the smoke and poor MPG. With regards to engines, you will get better sevice from a Cummins specialty shop than if you take it to a Freightliner dealer. A lot of independent shops work on the little Cummins engines also. The money you spend to get it repaired will be more than made up for with the money you are blowing out in smoke right now. You'll rest assured have better power also with it running right.
-Weave-

 

[Twmaster]

> The money you spend to get it repaired will
>be more than made up for with the money you are blowing out
>in smoke right now. You'll rest assured have better power
>also with it running right.

No truer word to be said. Not to mention all the extra crud getting in your oil from the unburned fuel.

--
Mike N