DIC is not accurate

[Dannyboy]

Everytime I fill up the truck I do out the fuel mileage by dividing the amount of miles I went by the number of gallons it take at the pump. The DIC always tells me a mpg higher. If the DIC tells me 17.3 it is really 16.3 give or take a tenth. And it always take about a gallon more then what the DIC "fuel used" tells me.

The truck is all stock. I do have a soft bed cover.

Is yours the same way?

[Kennedy]

Mine is about as dead nuts as it could be on my 2005.

Is your truck bone stock down to the tire size?

I did hit 23.4mpg DIC vs 20.6 mpg hand calculated this weekend runing a power box which skews mpg calc...

[jbplock]

Originally posted by Dannyboy:
... The DIC always tells me a mpg higher. .. And it always take about a gallon more then what the DIC "fuel used" tells me... Is yours the same way? My 03 with on power mods and stock tires behaves the same way... ??

[Dannyboy]

stock tires and no mods.

[DmaxMaverick]

Have you dealer check it out if it was accurate before, and not now. You may have in internal fuel leak, which will skew the DIC MPG. It could be as simple as a program update.

[mjammer]

My DIC runs a little optimistic (reads better than real life). I have been tracking it since day 1 and it averages ~3.5% or about 0.5 MPG off. If I have alot of city driving, it is off more than interstate. Interstate is almost dead on to reading a little low.

[mcmonroe]

Originally posted by Dannyboy:
Everytime I fill up the truck I do out the fuel mileage by dividing the amount of miles I went by the number of gallons it take at the pump. The DIC always tells me a mpg higher. If the DIC tells me 17.3 it is really 16.3 give or take a tenth. And it always take about a gallon more then what the DIC "fuel used" tells me.

The truck is all stock. I do have a soft bed cover.

Is yours the same way? My 2004.5 LLY is exactly the same way. After running through a full tank it usually holds one gallon more than the DIC shows as being used. This has held true over a wide variety of driving and towing.

Truck is 100% factory original currently with about 18,000 miles. I bought the truck new.

I wish it was more accurate.

Mark

[Dave]

DIC. Mine is also very optimistic. Yesterday it said I averaged 15.6 mpg, and used 25.5 gallons of diesel. I filled the truck with 28.1 gallons of diesel, which calculated out to 14.2mpg. The truck was fueled at the same pump and station by me. So far both fill up have yeilded about the same results, DIC indicating about 2 gallon less fuel used and anbout 1.5 mpg better milage. Truck is 100% stock.

Definatley does not get the milage my 01 did. Only differance between 01 an 05 is 2x4 vs 4x4 (05) and Hot Juice on 01. Plan to add Juice to the 05 soon, real soon as I miss the power.

[riverrunner]

You might want to check the accuracy of your odometer. Mine has an error of .055 (5.5%) per mile as measured by both interstate mile markers and GPS. I attributed it to bigger tires, but even with stock tires it could be wrong. When I account for the mileage error, my MPG calculations after refilling the tank come very close to DIC.

[Freeman777]

I have a suspicion that idling may account for some of the discrepancy in the accuracy of the DIC. I think it's normal for diesel rig owners to do a lot of idling: warming up; cooling off to shut down; fueling, traffic stops, running the air or heater while parked; etc. Recently, I had to leave my dog in the cab on a hot day, so I locked it up and left the air on. Out of curiosity, I zeroed out my DIC to see what my idling fuel usage was. It used .6 of a gallon over approx. 35 minutes. So I'd say a gallon per hour would be a fair rule-of-thumb. This may help account for the added fuel use and lend accuracy to the DIC mpg's? Other's have claimed and I have also noticed that highway miles vs. fuel consumption (from point A to point B) are easier to reconcile than inter-city driving statistics. Just a theory.

[Dave]

I do not do much if any idling with my truck. No cool down unless it was pulling a load. Warm up is only 1 to 2 minutes max. DIC is still way off.

[DmaxMaverick]

Idling should not be a factor with the DIC. The computer calculates fuel consumed/miles traveled. If your fuel usage figure is accurate, even when idling, it should not effect the overall mileage. Of course, the mileage will decrease with more idling, as fuel is used with no odometer increase.

If your accuracy becomes more skewed with more idling, I believe it is exaggerating the root cause of the reason for being inaccurate initially.

If your DIC mileage is not accurate, the only explanation is one, or more, parameter is not correct. The computer algorithm is only as accurate as its input data. Remember, "GIGO"?

[fourtenposi]

So do you guys think some of the powerchip companys are messing with tiresizes and gear size programming to give people the impression they are getting better fuel economy?

[JD Diesel]

Mine seems to be pretty close filled up to day dic said i used 20.7 took on 20.9 not that far off milage estimates are only off 2to3 tenth of a mile not to bad :D

[Dannyboy]

I filled up saturday, the dic said 18.8 gallons used and it took 20 gallons. The mpg said 15.9 and on the calulator it was 14.9. I checked the truck against highway markers and it seemed accurite.