Actual Fuel Economy

redkaz04 · July 21, 2011

First off-I love finally getting back into driving a lifted truck, I don't expect great gas mileage, non of us that buy trucks are going to get what a prius gets on the road. I have a civic for around the town. I am not complaining about fuel mpg with a lifted truck. SO...

However, driving home yesterday over the course of around 75 miles, DIC said I got an average of 13.8 mpg. The computer has not been adjusted or tuned for the larger 35" tires. With that in mind, isn't the current mpg it is reading based on the distance traveled on stock size tires?

Didn't I travel farther with the larger tires than the computer thinks I did? So isn't my mpg better than what the DIC is stating?

My gps tells me that I am driving 5mph faster than the speedo is reading. So in theory if I travelled 50 miles in an hour based on the DIC, haven't I actually traveled 55 miles in my hour? A 10% difference? So did I actually get 10% better fuel economy on my way home than my 13.8 the DIC recorded?

OR is that not correct at ALL....ahaha? Someone knowledgeble help me out here......

hrspwr · July 21, 2011

The best way is to do a hand calculation. In theory yes you would get better than what the DIC says, but I have a stock truck and the DIC is never right.....it is close, but it is always off.

redkaz04 · July 21, 2011

The best way is to do a hand calculation. In theory yes you would get better than what the DIC says, but I have a stock truck and the DIC is never right.....it is close, but it is always off.

So begin with a full tank, use mile markers, drive a 100 miles and then fill back up? The DIC has to be close on a stock truck..

But if the DIC was correct is everything I stated above correct based on my math?

cghbuilder86 · July 21, 2011

What you are assuming here is probably close. The bigger tires should help give a better number than the dic is going to show.But, that being said the dic "almost" always shows higher figure than you are actually getting. Mine is always 1 mpg better than I am actually getting.

redkaz04 · July 21, 2011

What you are assuming here is probably close. The bigger tires should help give a better number than the dic is going to show.But, that being said the dic "almost" always shows higher figure than you are actually getting. Mine is always 1 mpg better than I am actually getting.

I am going on vacation this weekend. I'll start with a full tank, take my gps record 200 miles, fill her up, do the math and see what i am getting then.......o and I will reset the DIC too at the beginning and compare the results.

Doug_Scott · July 21, 2011

When I switched to 4.10 gears from the 3.23 gears the DIC still showed me getting the same mileage. I wonder if the ecm/tcm/bcm modules have some form of gps in them, and the use that for getting information. I should have been getting incredible mileage if it used the speedo/odo for data. At 100km/h, the speedo said somewhere between 130 and 135 I think. I was still getting the 13l/100km I used to get at 100km/h. Once the speedo was corrected, I am getting 13l/100km at 100km/h.