View Full Version : Checked my DIC mpg vs. calculated

07-30-2010, 11:38 AM
Ran a comparison of my DIC to calculated mpg. I filled up, drove 415.5 miles and refilled. My DIC indicated a 27.2 mpg average. My tank held 15.65 gallons which calculates a 26.55 mpg. Better accuracy might be determined with more fill ups but the DIC isn't far off if any.

Also my miles to empty read 57 miles. Who knows, might go 500 miles on one tank before the engine actually stops.

This was my 08 A6, 2.73 geared, NPP C6 with headers, intake, UD pulley and tuning. We drove from Sugar Land, TX to Bishop, TX. Speed was 70-75 mph. Of course there are quite a few small towns along the way so there was some start and stop driving included. Not to mention several pit stops.

At a steady 70 mph my instant mpg reads from 34 down to maybe 29 or so. Seems as the temperature, humidity, wind direction/speed, road surface variables or maybe just the DIC fluctuations tend to create different reading at the same speed. By 75 mph don't remember seeing more than 30 mpg. Ambient temps were anywhere between low 80s starting out to 96* by mid day.

I noticed too during a fairly hard shower my mpg went down about 4 mpg. I suppose there is some drag on the tires from water, higher humidity maybe be a factor and/or maybe wind drag with water on the car.

07-30-2010, 04:46 PM
nice very nice

08-03-2010, 11:19 PM
I too was very interested in the differences Larry. I documented my drives from Metro Detroit to DFW area with a 346 and then with the 402 from metro detroit to burbs of Atlanta. At any rate I found the C5's DIC had around a 10% error on the high side. The c6's must be more accurate. Thanks for sharing the info. Its amazing to me how theys powerful no displacement on demand v8s can get such excellent gas mileage.

08-04-2010, 07:26 AM
I checked the DIC vs. reality on my C5 and it is high by about 1.5 mpg.

Pro Stock John
08-04-2010, 09:42 AM
Very interesting. Stock tank holds 18 gallons?

08-04-2010, 10:00 AM
Very interesting. Stock tank holds 18 gallons?18 is correct. Based even on my higher DIC reading it won't go 500 miles.

Pro Stock John
08-04-2010, 01:36 PM
You'd probably get better gas mileage at 65mph though right? I notice on cross-country drives with my MDX that I am hitting 24 mpg at speeds lower than 70 mph.

08-04-2010, 01:44 PM
Can't remember for sure but seems like I've read 36-38 mpg in the 50 mph range. Seldom get that slow! LOL! I'll have to take a reading next time out.

I only have to average 27.78 to get 500 miles on a tank. That would be easy on all highway and no city driving.

Pro Stock John
08-04-2010, 01:47 PM
A bit of a tangent but what does the car weigh now, and have you made any 1/4 passes in the current configuration?

Folks are always shocked at the fuel economy of a Corvette, my co-workers could not believe that my C5Z got 27mpg.

08-04-2010, 02:06 PM
The last track outing I ran an 11.77 @ 119.81 mph with a 1.87 60'(slight spinning). Z06 manifolds, Airaid intake, UD pulley and tune. DA +400. I have since installed Kooks headers. Don't know if I will make more power but they are about 20 pounds lighter. Also put in a 21 pound battery. Factory was 34#. Seems like I read somewhere that headers will get you about 10 hp over the Z06. Have not weighed the car with headers but I believe around 3350, maybe less, (with me) depending on amount of fuel. It did weigh 3380 one time out so I'm guessing on the 3350.

Pro Stock John
08-05-2010, 10:42 AM
Nice, let me know if you race the current setup I'd like to see how you do.

08-05-2010, 11:45 AM
It will have to get a little cooler before I track it again. Maybe when we get some nitrous air I'll see a low 11!

08-05-2010, 02:44 PM
My DIC is usually pretty accurate. I don't check my MPG anymore, but when I used to check it against the DIC, it was usually was only off at the most by 1/2 MPG.

I average 20MPG because I do LOTS of city driving and I don't drive like I should to conserve fuel. I run through the RPMs and I give it gas on the regular. I averaged 25MPG going to and from Vegas with some mild driving out in Vegas.