2006 2500HD diesel MPG and gallons used in DIC

Anyone know how accurate the readings in the DIC are for average MPG, and gallons used for 2006 model year Chevy trucks?

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on Sunday 11 November 2007 01:25 pm, someone posing as Ed H. took a rock and etched into the cave:

I don't know about those of you oil burners but I've found my DIC to be quite accurate. I was very meticulous on my mileage for about the first ten months of owning my Avalanche.
Now, after 13 months, I've slacked off.
--
www.perfectreign.com

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Mine is a 2005 2500HD, not a 2006. For me, the gallons used reads a gallon or 2 low over a full tank's usage. As a result, the mpg reads 1 to 1.5mpg high. I've gotten the impression that the gallons used sensor has sloppy calibration. You may get lucky.
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Wonder if there even are sensors. Bet it's all software. The computer has MPH, throttle position, RPM and so on. It may just be a calculation.
Al
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Greetings,
When I recently stepped up my tire size from 245/75 to 265/75 in my 2004 2500HD I did notice a few issues - the calculated MPG dropped by about 1.5mpg, the speedometer was now off by 3 mph at 70mph (Speedo reads 70, GPS reads 73 where before they were both the same), and the indicated mileage traveled dropped for the same distance. All to be expected when using larger rubber.
When I checked with my local dealer about reflashing the computer to accept the new tire size the service advisor advised against going through the trouble. Why? Well it seems that speedometer/mileage error that is acceptable to GM can be as high as 4% from the factory and since my new tires were around 3% different than the stock tires I was still within the margin of error.
Wished I'd have know that sooner - I would have put the larger tires on earlier and made the warranty last a little longer!
Cheers - Jonathan

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Thanks to all for the responses. It sounds like it depends on the vehicle. I'll just have to check it out for a while.
wrote:

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lower miles per gallon than actual and the gallons used will be greater than actual. When towing it is just the opposite, the gallons used will be lower than actual and the miles per gallon will be greater than actual.
The gallons used are rarely off by more than 1 gallon whether I am towing or driving solo. A one gallon difference over 25-30 gallons is probably within the acceptable error margin.
Ron
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