For the past few months I've been having horrible gas mileage in my 8. I average about 120 miles on a full tank (all city driving) occasionally redlining but usually shifting at about 4k rpm. I've been checking everything that I can related to gas consumption.
Did my spark plugs, wires and coils 4k miles ago cleaned my air filter, MAF sensor and ESS sensor. Recently went catless a few weeks ago and my car still has no CEL. I usually premix, and even after going catless I've still been getting the same MPG. I was thinking it might be my fuel pump failing but my car has no problems running, It redlines and accelerates fine without any problems.

I've also been looking for fuel leaks and so far haven't found anything or even smelled fuel. I've opened the lid under the rear passenger seat and looked at the connection to the fuel pump and it was all dry with no leaks in sight (actually really dusty) I also checked the fuel lines under the hood (blue and red clipped connections) while the cars running and while its off and, no leaks I didn't exactly buy an 8 for fuel conservation but everyone I know with an 8 along with most people on the forums here seem to average over 200 miles to a tank which leads me to believe there's something wrong with mine.
Is there any other connections that might possibly cause a leak? Or fuel pump problems that could be giving me this kind of mileage?

 

Have you tried re-setting the ECU?

 

How about some mpg numbers instead of mpt numbers.

 

As in the 20 stomp brake pedal method? Have not tried this.. and will do.

I really don't have an accurate method of measuring MPG so I've just been setting the trip computer. So I'm guessing 120ish/16 would give me an estimate of Mpg.. According to that I'm getting an average of 7.5mpg? This is mainly city driving all stop and go.. I need to get a device to measure my MPG asap. Other than the trip computer.

 

You can download an app on your phone where you can enter in basic information when you are filling up to log your MPG.

 

^Thanks I'll look into that. I just reset my ECU (using the 20step brake pedal method and the trip computer method) and filled up a full tank. I'll observe and try to better gauge any differences on MPG.

 

Why do you think you need a device to determine miles per gallon? It's simply miles on tank divided by gallons to fill at the end of that tank. (not a "16" guess).

If you are only driving in city, you may get as low as 12 mpg, depending on length of trip, start/stop cycles, driving style, weather conditions, terrain, etc. It can vary widely. If you want a better benchmark about your mpg (which is one indicator of engine condition and tune), take it on a long trip without city driving. If you keep speed between 65-70 you shouldn't see any less than 21 mpg or so...

 

Thanks. I'll try that method. I usually fill up at about quarter tank. So in reality my average was about 120 miles per tank on about 13 gallons which is about 9mpg.

 

When I fill up after the light it is usually right at 14 so your 1/4 tank is probably 11-12.

I use Gas Cubby for iPhone to keep track of mpg and maintenance schedule, cost and trends. My average is 18.1 over the 3 months I've owned it but mostly because of one long road trip. My city average is between 13-14.