Fuel economy.

I'm trying really hard to gauge my MPG in my 91 but its difficult to tell as the speedo is off by anywhere from 5-7 mph

For the most part I think 20 mpg is doing really good for the IDI. They have a big displacement and the Stanadyne injector pump neither of which help in comparison to the competition. My truck seems to do good with my camper (I'm guessing somewhere around 15-17) but the turbo and IP don't seem to work in conjunction with the engine though out the majority of the power band. I really wish we had Bosch pumps (or something with an altitude compensator) and better matched turbo's. I think that would help out a lot.

That said I can't believe how often I switch my front tank to the rear right at 208 miles. It's like clockwork every time not matter how I drive it

Well I've got a completely fresh fuel system, 1 year rebuilt C6, fresh wheel bearings on all 4, it's 2wd, no leaks anywhere and I only get 12-14 mpg with 70% city driving. I've verified my speedo with gps as well and I never get on the go pedal. I love the old beast and it's been great to me, but it's never been very fuel efficient. Timing is set to 9.0, 176k. Luckily I only have a 9 mile commute

matt-jenkins said:

So, this fill up I got 300km to the tank, 60 less then i got when I calculated it last time. Im also getting hard starts as well, I think it is time for a new fuel system.
Pensicola diesel seems to have the best price on a reman pump and injectors. I'm N/A so i dont care about getting performance parts but is there stuff usually pretty good? Anyplace else i should look besides moose products?

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Any local shop thats been in the business for many years would be worth a look too. However Mel does offer a "baby moose" that is simply a higher quality stock calibrated pump at a lower price than the moose. Pensacola can be a bit of a hit and miss company from some other feedback, but most of them seem to run ok.

Brianedwardss said:

Well I've got a completely fresh fuel system, 1 year rebuilt C6, fresh wheel bearings on all 4, it's 2wd, no leaks anywhere and I only get 12-14 mpg with 70% city driving. I've verified my speedo with gps as well and I never get on the go pedal. I love the old beast and it's been great to me, but it's never been very fuel efficient. Timing is set to 9.0, 176k. Luckily I only have a 9 mile commute

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Unfortunately, its your short urban driving cycle that is killing you. Mine probably wouldn't deliver much better under the sam conditions. If I drive with eggshell acceleration and coast up to stoplights I might be able to get above 16 MPG but most of us don't have that kind of patience (not to mention drivers behind). Sad reality is these trucks make terrible daily drivers.

Rot Box said:

For the most part I think 20 mpg is doing really good for the IDI. They have a big displacement and the Stanadyne injector pump neither of which help in comparison to the competition. My truck seems to do good with my camper (I'm guessing somewhere around 15-17) but the turbo and IP don't seem to work in conjunction with the engine though out the majority of the power band. I really wish we had Bosch pumps (or something with an altitude compensator) and better matched turbo's. I think that would help out a lot.

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I think it's worth noting that the GM 6.2l and the early 6.5l's basically run the same injector pump we have...it's reverse rotation and IIRC there are a few other internal differences, but it's still basically a Stanadyne pump. And, I agree completely with the desire for a Bosch-designed fuel system!! I've said before and I'll say again that the Stanadyne fuel systems are the Achilles heel of these engines...

david85 said:

Unfortunately, its your short urban driving cycle that is killing you. Mine probably wouldn't deliver much better under the sam conditions. If I drive with eggshell acceleration and coast up to stoplights I might be able to get above 16 MPG but most of us don't have that kind of patience (not to mention drivers behind). Sad reality is these trucks make terrible daily drivers.

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Have to agree with that also...these trucks want to be moving down the road on a long-distance run, not driving short distances. I had to use my truck as a daily driver for about 2 years (although I have a 20 to 30 mile commute, there's a rather large hill I have to climb up and down close to home...on my drive to work, I can't avoid hitting this hill before she's fully warmed up), and she didn't like it one bit.

i finally had a reason to run an entire tank out (plus a bit) out on the interstate running empty.i just ran down to New Hampshire to pick up a hydraulic lift gate for log truck!
fillup date: 2014-05-01

basic recap:
f250 4wd
E40D auto (hd reman with custom extra low stall converter/tugger kit)
srw to drw convert.
3.55 R&P with shorter than 235 tires for an effective gear change to 3.84
111k miles on 7.3l idi
banks turbo
intercooler
maxed oem n/a ip (a reman that i swapped in around 70k miles.reman by IFS from the U-haul idi parts clear out back along)
fresh (new) G codes
electric cooling fans
8k lb empty
enclosed stake body,box truck
engine timing 7 BTDC (pulse/ferret adapter)

http://ecomodder.com/forum/em-fuel-log.php?vehicleid=5088

oh come on.someones got to think that's decent! ^
the electric engine cooling fans didn't have to turn on at all.not once the entire trip.on the hwy nor the city.too cool out still.was nice down in NH though.in the 50's! that felt good.

i don't think i'll ever find out what log truck could do....least i hope the day never comes where i have to run her out for a few hundred miles with those 5.13's lol........would be a long slow trip at I95's minimum speed of 45 mph.

Pretty good. Lol


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