How far is your computer off?
Thread Starter
Advanced
Joined: Apr 2003
Posts: 99
Likes: 0
From: MN
How far is your computer off?
I track the mileage I get and compare it with the computer readout. The DIC mileage seems to be consistently about 10 to 15 percent high. On a given tank of fuel, it says average mpg of 25, but when I calculate it out, it works out to 22 something. I know that one fill is no measure, because you cannot always fill it exactly the same, but over a number of fills, you can see the pattern. Anybody else see this kind of error? Could ethenol be causing the problem? Like if the computer were calibrated for pure gas and now we burn some alcohol in the mix? Hmmm. 10% error. 10% ethenol. Coincidence?
Race Director
Joined: Apr 2001
Posts: 19,329
Likes: 16
From: Saint Augustine, FL
Mid-TN Events Coordinator
St. Jude Donor '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16
Originally Posted by 87SAM
Mine seems to be about 2.0 - 2.5 MPG optimistic on either a city driven tank or highway tank.
Mine almost always is off by 2 MPG (computer reads 2MPG more than the actual MPG).
Pro
Joined: Jun 2005
Posts: 568
Likes: 0
From: Wichita KS
Originally Posted by 87SAM
Mine seems to be about 2.0 - 2.5 MPG optimistic on either a city driven tank or highway tank.
Racer
Joined: Feb 2005
Posts: 342
Likes: 0
From: Kearney NE
Originally Posted by mr_dakota
I track the mileage I get and compare it with the computer readout. The DIC mileage seems to be consistently about 10 to 15 percent high. On a given tank of fuel, it says average mpg of 25, but when I calculate it out, it works out to 22 something. I know that one fill is no measure, because you cannot always fill it exactly the same, but over a number of fills, you can see the pattern. Anybody else see this kind of error? Could ethenol be causing the problem? Like if the computer were calibrated for pure gas and now we burn some alcohol in the mix? Hmmm. 10% error. 10% ethenol. Coincidence?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Thread Starter
Advanced
Joined: Apr 2003
Posts: 99
Likes: 0
From: MN
Originally Posted by Jeff Jeff
Are you resetting the avg MPG each time you fill up?
Intermediate
Joined: Apr 2001
Posts: 46
Likes: 0
Originally Posted by BlackArrow
On a 3400 mile road trip mine was very accurate....less than a mile per gallon off.
On two long road trips, I did a comparison between the computer and actual usage and both times the computer was .7 to .9 mpg high. I consider this extremely accurate. However, I did read somewhere(can't remember where) that the computer resets on the mpg reading every 400 miles. Can anyone confirm this?
Paul
Safety Car
Joined: Jan 2001
Posts: 4,389
Likes: 693
From: Boise ID
Originally Posted by mr_dakota
Yup, reset everything whenever I fill it up. [B]My 96 DIC was very accurate. I suspect that there may be some truth in that they are programmed to read a bit high ("feel good"), but that certainly goes away when it is fueled up. One would think that they ("GM") would go for a longer range feel good than the first tank of gas. Truth is, I'm averaging about 22.4 per tank, and I'm not unhappy with that, considering the number of ponies I'm horsing around with. At my age (59) I also don't drive with as much as a lead foot as when I was but a youth.
Wil Cooksey #256
Joined: Jan 2004
Posts: 2,814
Likes: 24
From: Sacramento Kalifornia
I took a 6,800 mile trip this summer and reset the Average when I left and never touched it until I returned home. On the 2nd day in New Mexico it was reading a little over 29 MPG when I got off the highway for the night. By the time I went to dinner about 5 miles away, the Average was down to 27 and some change. On the highway the next day it went back up to 29. Mine is off and I'm really at a loss to figure out how the thing works. I believe to calculates the Average based only on the last 10 or 20 miles driven. The reason I say that is because even at 6,000 miles, the Average would go down about 2 MPG when I got off the highway and drive 10+ miles on surface streets.
Safety Car
Joined: Jul 2001
Posts: 4,661
Likes: 67
From: Ocean Springs MS
I read somewhere (can't recall where, but I think it was in a post here a year or so ago) that the computer does a rolling average on the last 20 gal of fuel used, unless it is reset, so a little over 600 mi is about as far as the DIC Avg MPG is good for.
FWIW - mine is usually 1-2 MPG optimistic, recent road trip said 31.3 MPG while I figured 29.9.
FWIW - mine is usually 1-2 MPG optimistic, recent road trip said 31.3 MPG while I figured 29.9.
Thread Starter
Advanced
Joined: Apr 2003
Posts: 99
Likes: 0
From: MN
Originally Posted by fdxpilot
I read somewhere (can't recall where, but I think it was in a post here a year or so ago) that the computer does a rolling average on the last 20 gal of fuel used, unless it is reset, so a little over 600 mi is about as far as the DIC Avg MPG is good for.
FWIW - mine is usually 1-2 MPG optimistic, recent road trip said 31.3 MPG while I figured 29.9.
FWIW - mine is usually 1-2 MPG optimistic, recent road trip said 31.3 MPG while I figured 29.9.
Burning Brakes
Joined: May 2002
Posts: 831
Likes: 0
From: Albuquerque NM
Only owned mine for 3 tanks, and it seems like the DIC is optimistic, but only by 1-2mpg. Mixed traffic/freeway it has shown as much as 23.3 and when calculated it came out to 22.5 
. I had a '97 K1500 that the same drive would get 13.8, and my '87 GN only gets 16.1. I can't get over that the vette gets that good!! And yes, I still drive it like a vette when traffic allows.
. I had a '97 K1500 that the same drive would get 13.8, and my '87 GN only gets 16.1. I can't get over that the vette gets that good!! And yes, I still drive it like a vette when traffic allows.
Administrator
Joined: Mar 2001
Posts: 368,536
Likes: 24,825
From: In a parallel universe. Currently own 2014 Stingray Coupe.
C7 of the Year - Modified Finalist 2021
MO Events Coordinator
St. Jude Co-Organizer
St. Jude Donor '03 thru '26
NCM Sinkhole Donor
CI 5, 8 & 11 Veteran
When I have tracked mine by hand calculation, it seems to be about 1 mile optimistic for the computer. Pretty close though in my book.