Ok I always knew rotaries didnt get the best gas mileage but this is kinda ridiculous. I put in $20 worth of gas yesterday morning, I figured this out to be just below 9 gallons. I drove 25 miles to work, 25 miles home, and about 10 miles worth of errands and gf pickup/drop off's. I then drove 25 miles to work this morning and im on E again. Thats 10 miles to the gallon, and most of my work drive is highway.

On another note, my fuel light have never come on no matter how long ive driven on E(out of pure necessity). SO am I really gettign the BS mileage or is my gauge off? Mind you almost all my other stock gauges are broken.

 

Wow that's crap milleage. The tank is 17.5 galons btw. If you are really getting that bad of milleage then you should look in the archives, there's a rather large thread in there for increasing fuel economy.

the best way to figure out ur economy is by filling the tank, driving a couple hundred miles as you would normally and then filling the tank again and whatever amount of fuel they manage to put in is how much you used.

 

You should be getting 17/19 stock and 19/22 with highflow exhaust and intake.

Sounds like time for a FULL tuneup, check the catalytic converter for clogs, fuel filter, air filter, fuel strainer (very unlikely), O2 sensor, water temp sensor, etc...

 

Got any exhaust leaks? Before the 02 sensor? That'll make you run even more rich.

I've got one now and i get like 10 mpg...

James

 

make sure that O2 sensor is working right. If not mistaken, you run pig rich when it does not work right, causing terrible gas milleage

 

Im gonna try replacing my O2 sensor later this week, i dont think i have any exhaust leaks, but i have no cats or any other emmissions equipment, the fuel strainer and filter are new also and the tank was very recently cleaned.

Im also gonna do the test locketine suggested to see if my gauge is reading right. Why would my water temp sensor effect gas milage?

 

The best way to determine gas milage is by taking the miles driven on a tank and dividing it by the gallons put in, not guestimating based on when you hit E. On my car I could be on E and still have 3 gallons left, easy. And for the record s4 gas tanks are 16.6 gallons according to the Haynes manual.
Theres a good possibility that you need to clean you injectors. Also, you might check you spark plugs, I think that can hurt milage as well.

 

carbon buildup on the plugs is common, especially on higher mileage engines. Having the injectors overhauled, blue printed, & flow tested will help some. It's still a good idea to clean the plugs every 15K miles.