When I fill up the trip computer says 160 miles to empty. I am getting less than 200 miles per tank. About 95% city mileage. 109k miles. I use 93 octane. Tires are all fully inflated. I drive relatively conservatively. Is there anything I can do to reset the ECU? Please help, my gas mileage is so poor I'm starting to regret having this car.

 

Is your check engine light on? Have you checked for any codes?

 

no codes. Just really bad mileage. Currently at 116 miles and i am between half a tank and quarter tank. You would think i was driving around WOT all the time but I actually drive quite conservatively. It seems like I'm getting around 5 miles per gallon.

For instance, yesterday i was at exactly half a tank with 100 miles on the trip A odo. I drove to the store and back, thats about 15 miles. It looks like i used over 2 gallons on that short trip. I drove in 7th gear and didn't go over 55 mph. I shifted early the whole time, keept rpms under 2500. What is going on with my car? Does anyone else see this kind of egregious mileage with their g37?

 

Don't look at it as a half tank and such. What's the car say for your fuel economy? When you fill up how much fuel are you putting in? Do a fill up and then do an actual calculation to see where you're at. Do you have an OBD scanner to check for pending codes? One of your brake calipers seized and putting a ton of drag on one wheel?

 

I do have a cheap 20 dollar scantool I can hook up. I d9nt believe I have a seized caliper as I am highly attentive to every mechanical aspect to my vehicle. I only recently bought this car 2 weeks ago. My mother used to drive it and she drove like a grandma and always took it to the stealership for all maintenance. As for the Computer, it says 67 miles to empty currently. So in that case maybe I'll see close to 200 miles from a tank which at this point would be like a blessing.

 

What is the instantaneous fuel economy display showing when you're driving at a steady speed?

 

Where are you getting this information from: the gauge cluster center display, or the Vehicle Information Screen in the AV unit/ center dashboard screen?

First and foremost, as Epiphany suggested, do a ACTUAL mileage calculation. Fill up the tank, reset the trip odometer AND the "Average Fuel Consumption" monitor. Then, drive NORMALLY. Do not short shift, avoid jackrabbit starts and sudden abrupt stops- let the car do what it was designed to do. When the gauge gets near 1/4 tank or so fill up again. Divide the miles traveled by the number of gallons used to fill up the tank. This will give you your actual mileage per gallon reading. You can also compare your calculation to what the "Average Monitor" reports. Your calculation will be the most accurate, however.

Also, as Selym suggested, what does the "Instantaneous Fuel Consumption" bar graph read as you are cruising about?

A sensor could be malfunctioning, gas level sending unit could be gummed up, could have a mechanical issue. Too many what-if's. Don't rely solely on what the computer reports.Grab a pen and paper and do it yourself. If you are still getting abysmal mileage, THEN, you can go forward diagnosing any issues.

I average 400-425 miles per tank... and I drive like Grandpa Munster....

 

basic tune-up couldn't hurt either - how long since the air filters have been changed, change the oil to use the proper stuff, check spark plugs which might be carbon'ed up from your mother's driving habits.

BUT - first do the manual calculation. The computed fuel economy and miles remaining are based on a lot of assumptions by the computer and aren't all that accurate (long term fuel mileage average on the nav display should be close, though).

 

Never got more than 365 miles per tank on my G but then California is pretty much all stop-n-go driving no matter where you go anymore

 

Is the OP driving in lots of stop and go traffic? Accelerate gently? With over 100K miles, the o2 sensors could be deteriorating/lazy (not responding immediately). Or as mentioned, some other sensor could be causing issues.

Most of my urban mpg in the 6mt was in the high teens/low 20's (19-21). On the hwy better at 24-25.

This is what I get in the 4 banger stinger after a highway run. This does somewhat correlate to actual calculated mpg - ~low 30's on the hwy, low/mid 20's urban.