Thread: Bad Gas Mileage

Glad I could set your mind at ease Ace. Hehe Although it is probably showing, fuel efficiency is kind of a hobby of mine. (Ya ya I know )

mlasnoski, you are absolutely correct. The car uses a combination of the speedometer and the engine hour gauge to take into account idle time in the average speed calculation, this is a very useful tool. Although a person could come to really messed up conclusions using the instantaneous DIC readings (they tend to all over the place), however over the course of a couple fill ups you can get some really good data.

As I mentioned earlier the faster average speed you have, your mpg will track up with it. In my experience you hit a wall at about 50 mph average speed, then mpg will start to track down with speed increase. This is of course due to aerodynamic loses at higher speeds.

The truth is GPs are awesome highway/interstate cruisers, and they get great mpg under those conditions. But they really take a big hit in stoplight to stoplight city driving, as due most midsized vehicles.

Originally Posted by cerick08GP

Although a person could come to really messed up conclusions using the instantaneous DIC readings (they tend to all over the place)

When you say instantaneous readings am I missing something? I didn't think there was a way to check "at the moment" mpg readings. I only have an option to see averaged readings on my DIC. Is there a trick to seeing instant readings?

Yes, my GP has an instantaneous mpg read out. However, as I mentioned earlier IMHO it isn’t very useful as it pounces around quite a bit even when the car is operating at/near steady state.
I’m pretty sure all GPs with the 5-button DICs have this feature, but I’m not sure when they added it. Just a guess but it was probably around 05-06 model years. If you do have it, you can display it by pushing the button with the gas pump symbol on it and cycle through the options until it reads “INST ECONOMY”.