01 RS, manual, 72xxx miles

noticed my mileage was down last 5 fillups or so (I gas up about every 3 weeks). Thought it was just crappy Costco winter formulation, haven't changed anything, car doesn't seem to be running poorly at all.

So I did what any reasonable owner would do, check my tire pressure and clean the Amsoil air filter, still no good.

What do I check next? Definitely replacing fuel filter next service (in 1k miles), and I'll try filling up elsewhere for my next tank.

 

man, i wished i could fill up every 3 weeks...


hell, if it was one fill up per week i'd still be smiling ear to ear.

 

check your engine compression. something could be wrong with one of the cylinder.

 

if I filled up every 3 weeks and got 10mpg I would still be happy

 

go to winchester auto, get some redline fuel system cleaner and a new fuel filter. Replace the filter, put it in a near empty tank, fill up at a 76(newer remodeled one), go drive the hills. Run the fuel system cleaner through at least 2 tanks of gas.

I was getting poor mileage and low performance around 60-70k miles in my wrx. did this and it made a huge difference.
Under high load the Injector duty cycle was going to 105% but the car didn't feel so great. Duty cycle went down to the 90-99% range and felt much much better.

 

i noticed my gas mileage is down by almost 20-30% since i went to stage 2 with TBE on my 07 WRX and i only have 14k miles on it.

 

see, when people say modding and tuning will increase your MPG, they mean it has the potential to increase your MPG, however most people prefer to use that extra power.

Given its raining here and my tires barely have legal tread, I'm running Cobb's econo map (yeah, it makes you granny drive, but I'm not going to be flooring it now anyways)

 

The 'potential' seems to end just south of my right kneecap.

Whats your mileage difference running the econo map? I probably wouldnt run it for daily driving, but if I was doing a road trip then yeah.

 

When's the last time you did an oil change...

I know my gas mileage shoots up for the first 1k miles after an oil change.

 

The sudden drop from @23mpg to @18mpg just has me a bit worried. Also I've always had a lot of soot on the tailpipe, though this seems to be common with the 00/01..

I'm due for another in under 1000 miles, so I'm towards the tail end of things.

Mobil 1 5w30 since the second oil change.

This is a good idea, I get my oil filters from there anyway.

 

oil, and O2 sensor, those have always been the two things I've always known to do it.

 

Reset your ECU. Maybe your car shut down the turbo or somethng (ala no waste gate duty)

 

once every three weeks? wow.. the longest i've gone was 7 days lol... i usually fill her up every 4-6 days

 

What the...only 72k miles on that thing

 

I used to carpool.

So I'm going to do the injector cleaner/new fuel filter/different gas route and see what happens.