Since instant mileage is not available on my truck, and I don't want to keep resetting the average mileage, the following technique seems to work well for determining "instant" mileage.

- Using the DIC, set the road mileage display on trip meter, and the fuel display on gallons used.

- As soon as the gallons used increments by 0.1 tap the road mileage button and make a mental note of the mileage (only need to remember the ones and tenths places- ie 1345.2 = 5.2).

- Switch back to the fuel display and wait for it to increment by 0.1.

- As soon as the gallons used increments by 0.1 (for the second time) tap the road mileage button and make a note of the mileage.

- Subtract the first mileage from the second mileage then multiply by 10 to determine your "instant" mileage.

Using this technique, I found that I get 25-30 mpg over the road, although my average (around town) stays around 17-18.

You sir, are a Genius!!

Thanks, but not really. The geniuses are the guys that can reverse-engineer the GM engine control module, then re-program it to add an 100 hp... Or the guys that figured out how to retrofit LUX/NAV from an Escalade to a Silverado with just a few wiring and hardware changes.

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Using this technique, I found that I get 25-30 mpg over the road, although my average (around town) stays around 17-18.

If you can swing by Ohio and make mine get 25-30, I'd be greatly appreciative. You must be doing this calc. while driving downhill with a tail-wind. Also keep in mind that the gallons used is a "guess" by the DIC. It does NOT actually meter the fuel flow through the fuel rails.

I wish we got 25-30, but it ain't happening. Get used to the 17-18.

Since instant mileage is not available on my truck, and I don't want to keep resetting the average mileage, the following technique seems to work well for determining "instant" mileage.

- Using the DIC, set the road mileage display on trip meter, and the fuel display on gallons used.

- As soon as the gallons used increments by 0.1 tap the road mileage button and make a mental note of the mileage (only need to remember the ones and tenths places- ie 1345.2 = 5.2).

- Switch back to the fuel display and wait for it to increment by 0.1.

- As soon as the gallons used increments by 0.1 (for the second time) tap the road mileage button and make a note of the mileage.

- Subtract the first mileage from the second mileage then multiply by 10 to determine your "instant" mileage.

Using this technique, I found that I get 25-30 mpg over the road, although my average (around town) stays around 17-18.

the dic, with gallons used, isnt as spot-on as the mileage divided by the number of gallons filled up, though. Especially if you have a programmer

the dic, with gallons used, isnt as spot-on as the mileage divided by the number of gallons filled up, though. Especially if you have a programmer

:exactly: Mine is usually off by about 1 1/2 gallons.

If you can swing by Ohio and make mine get 25-30, I'd be greatly appreciative. You must be doing this calc. while driving downhill with a tail-wind. Also keep in mind that the gallons used is a "guess" by the DIC. It does NOT actually meter the fuel flow through the fuel rails.

I wish we got 25-30, but it ain't happening. Get used to the 17-18.

I don't believe that I indicated that I was AVERAGING 25-30. "Instant" - yes. Average-no.

If you try the "instant" mileage calculation you might be surprised. It doesn't take a lot of horsepower to maintain 60-65 mph and with the steep overdrive gearing of the Allison, the engine is hardly turning over.

Measured instant mileage again today driving steady 65 mph into a good headwind and it was in the 17-20 range. My DIC is conservative and it always indicates a little more fuel used than actual. But I still get a little nervous when it indicates 23 gallons used and the low fuel light comes on...