..

 

Get it to a company that can run it on the rollers and check the map. EngineTuner are in Plymouth, try them.

15mpg isnt great but could be expected if raggging it to death. Mothering it should get closer to 30mpg

 

Check for brakes binding?

 

I wouldn't even describe it as needing mothered to get close to 30mpg. I am by no means a slow driver on backroads up here and even then I struggle to get less than 22mpg as an average. 15mpg sounds like something seriously wrong, or the owner is a serious risk to people on the public road!

 

I used to average 240 miles to a tank full in a 05 blob wagon, and my record was 355 miles on a long run through France. However, everyone uses a shed load when new to Subaru, imo!

 

It’s interesting you say about the PPP as my WRX has the PPP (inc ecu) and it’s diabolical on fuel.

I’ve never worked it out but I know it doesn’t matter how you drive it, it just drinks like mad. Only reason I know it’s bad is because I have an STI with a custom ecutek remap and it’s noticeably better on fuel. Not saying the sti is particularly great but I do notice when I use my WRX it uses a noticeable amount more fuel.

 

As your in Plymouth I’d get it to enginetuner for a check over, I’m sure if there’s Anything wrong he will find it as he’s one of the the best in the business.

 

I have an '02 and '05 WRX both with PPP. Driven 70k+ combined. I've measured the MPG via full to empty tank refills countless times and they have always been ~28mpg with mixed driving over ~300 miles to tank.
Always.
I don't even bother checking them now. It's not possible to thrash them continuously for a full tank on public roads. Even if you drove hard whenever the opportunity arose, it will still be above 20mpg for a full tank on a daily driver. Anything less than that and there is a serious fault. There will be either an air leak or a faulty O2 or Temp sensor or something similar that is telling the ECU that there is more air entering the engine and therefore the fuelling needs to be increased.

WRX PPP is cat-back exhaust, silicone Y-pipe and flashed ECU. That's it. No fuel pump, no wheels, no seats.

If you get a decent OB2 reader it will either tell you the fault or allow you to log the engine values in real time and identify the fault.

Failing that, just take it to EngineTuner to diagnose and fix.

 

Take the above advice. Injector cleaners in tank are pointless. Enginetuner will diagnose it.

 

Hawkeye WRX worst tank 210 miles best 290 miles. I average between 21-25. Most journeys stop and start rush hour. Barely get to use 4th gear. Best tank was a 290 round trip down dual carriage and motorways. I did not even care about the fuel consumption on this journey if you know what I mean.

 

My old blob WRX wagon used to average somewhere between 27 and 30 mpg on most runs, when it was the 'stock' PPP setup. After I had a VF35 fitted and various other mods, and a remap, it actually got better on fuel despite having around 50bhp more! 15mpg is indicative of serious problems, either with the car or with your maths.

 

I have 2003 blob wrx with VF34 and pink injectors. 30mpg on motorway doing 70 or a bit better doing 50/60 mph trundling from Yorkshire to Norfolk. Can get 300 miles on a tank with a mix of commuting and a little spirited driving. Lots of spirited driving maybe 170/180 miles to a tank.

 

Blob eye wrx exhaust only got my best 345 miles other week ....was mostly a road 50mph tho....normal get 230 ish

 

Losing exhaust gas prior to the lambda sensor will affect fuelling.

 

2003 STI PPP

Average = 17mpg
Mothering = 19.3mph
Mothering plus lots of motorway done @ 50mph = 27mpg!!! Felt like Christmas

 

34mpg on a trip to Wales a few weeks ago 53 WRX.

Half motorway, half A-roads with a roundabout every now and then. Just did a fairly constant 70 on the motorway. Normal tank average is 23mpg ish on b roads and local roads.