Why am I getting 21mpg?

[Viper3812]

I used to actually get 19mpg, but now it's up to 21 and when I'm on the highway it is usually around 23 or 24mpg. Shouldn't our car get atleast 27mpg max in the early 30's? I use 93 octane gas and have my stock chip back in. Any possible reason why I am getting such low mileage?

[AutoM3otives]

Thermostat recently replaced?

[Viper3812]

No. Would that be a definite cause or could there be something else?

[tastade]

I get 22 city 32 highway, which is the EPA rated. I know most get better than that, and I do have a lot of black soot on the exhaust tip from running rich. My engine throws no codes, and I have recently changed the fuel filter, thermostat (helped 2 mpg in the winter), and changed spark plugs.

My next job is going to be to change the valve cover gasket as oil is pooling around one of the spark plugs, which might be causing a slight miss that could hurt fuel economy. I know many people clean their idle control valve, which might help, and their throttle body.

[BleMW]

I get ~30 mpg city and ~36-38 mpg highway - fuel lines help.. just a thought

[mohaughn]

I get 23mpg city driving in Orlando in my 328i. The Ti gets something like 27mpg in the city with my Jim Conforti chip.

The basic items to check for fuel economy are the fuel filter, air filter, spark plugs, plug wires, ICV.. The usual tune up stuff. Might want to try some fuel injector cleaner or actually replace your fuel injectors. I'd say your mileage should be a lot better than that.

[Viper3812]

My car as well isn't shooting any codes and is puffing out black smoke. I have changed my valve cover gasket and spark plugs about a year and a half ago and just changed my fuel filter last month. Still have the stock o2 senors and thermostat and I plan on cleaning the ICV soon because I'm having rough idles and engine stalling every once in a while.

[Viper3812]

Originally Posted by mohaughn

I get 23mpg city driving in Orlando in my 328i. The Ti gets something like 27mpg in the city with my Jim Conforti chip.

The basic items to check for fuel economy are the fuel filter, air filter, spark plugs, plug wires, ICV.. The usual tune up stuff. Might want to try some fuel injector cleaner or actually replace your fuel injectors. I'd say your mileage should be a lot better than that.

New fuel filter and fuel pump in, have a cone filter, might change spark plugs again, stock wires, need to clean ICV.

[tastade]

I also have the stock O2 I believe, and I also need to clean my ICV for the same reason, sometimes has a rough idle and rarely (5 or 6 times in 30k miles) has stalled on me.

Do people get better gas mileage in the M44 v the M42, or are people also getting 25+ mpg city driving in the M42?

[cosmos schwarz]

i've an m42, mileage varies too much, from 250 miles a tank to 400 miles. but thats on 99 ron. sorry cant work out mpg.

[kelso]

what wer you getting when you had the chip? ive been getting 27-29 lately with my chip in....maybe the stop chip threw something off?

[3DGE]

freeway I get 37mpg highway-city it can go from 22-27

[Viper3812]

Originally Posted by kelso

what wer you getting when you had the chip? ive been getting 27-29 lately with my chip in....maybe the stop chip threw something off?

At first I got 18 and 19mpg with the chip and then it moved to 21-22mpg and the same with the stock chip.

[adamud]

This probably isn't it, but have you checked your tire pressure in all 4 tires? That can make a good difference in mpg. Ive had a drop in mpg to. I can't find out what it is.

[kelso]

thats way off...bad o2 sensor? have you gotten your computer checked? i had a shop run mine and had a bad o2, and bad knock sensors, never even knew it...