Tuning Question! MPG doesn’t match full tank mileage!

JustinReed · Jun 20, 2018

I fill up my car, at the time I was averaging 14.5 mpg, but when my tank was full, my (miles to empty) read 187 miles, when it should be around 217 miles. I’m running 91 right now, not e85.

I’m also getting what looks like a carbon build up on my rear valance.

My car is dyno tuned, am I correct thinking that my car is tuned to rich, and that could be the issue of why my actual mileage isn’t matching what my gauge is reading?

Any help is appreciated, this is rather frustrating...

Zelek · Jun 20, 2018

JustinReed said:
I fill up my car, at the time I was averaging 14.5 mpg, but when my tank was full, my (miles to empty) read 187 miles, when it should be around 217 miles. I’m running 91 right now, not e85.

I’m also getting what looks like a carbon build up on my rear valance.

My car is dyno tuned, am I correct thinking that my car is tuned to rich, and that could be the issue of why my actual mileage isn’t matching what my gauge is reading?

Any help is appreciated, this is rather frustrating...

There's also a pretty distinct smell at idle for a bit when your car is running rich. The fact you already can see buildup on the rear is a bad sign. I would probably have your tune checked and do some data logging.

It will also help if you can monitor some of your stats while you drive like your AFR.

white15gt · Jun 20, 2018

The DTE on the dash is a 500 mile rolling average. It doesn't change based on the MPG on the dash

EFI · Jun 20, 2018

1) take miles to empty with a grain of salt

2) you can easily tell if your car is running rich or not just by looking at the gauge cluster and seeing what the AFR is. Should be high 13s low 14s cruising.

3) have you actually calculated the MPG/miles per tank or are you just frustrated at the poor estimation in the dash

JustinReed · Jun 20, 2018

EFI said:
1) take miles to empty with a grain of salt

2) you can easily tell if your car is running rich or not just by looking at the gauge cluster and seeing what the AFR is. Should be high 13s low 14s cruising.

3) have you actually calculated the MPG/miles per tank or are you just frustrated at the poor estimation in the dash

The only calculation I’ve done is the math of my mpg and miles to empty. Before, when I would average 15-16 mpg, my miles to empty would be much higher.

Tuning Question! MPG doesn’t match full tank mileage!

JustinReed

Well-Known Member

Zelek

Well-Known Member

white15gt

Well-Known Member

EFI

Well-Known Member

JustinReed

Well-Known Member