I get over 400 miles driving like a **** in a mapped 178Bhp vrs with both FMIC and ERG delete, can get up to 500 hundred if I drive sensible.

 

Only 250? wtf, there has to be something wrong with your car mate.

Are you absolutely sure it's not leaking fuel?

 

What about the return fuel lines to the tank?

How much fuel are you putting in each fill up?

Replace the coolant temp sensor it's only a £10 part

Mines returning 52.9mpg to and from Newcastle today

Try the shell v power fuel, cleaned no end of crap from mine, helped it run better and returned more mpg

I'd go with the italian tune up treatment to start with as you say the engine is healthy and runs well. Bung 20 quids worth of v power in it and a bottle of injector cleaner (redex is usually 2 or 3 quid in the supermarkets) then take it for a proper blast. 70mph in 4th gear (to save your driving licence) for 50 or 60 miles up the motorway then reset your trip and turn rond and head back at a normal speed and see if it appears to have helped.

 

I run an SDI with loads of veg oil and now and again use the v power/diesel cleaner combo to keep the engine clean inside.

The thing is, it's not like it's losing 40 miles which would probably result in driving like a granny all its life.

 

It's losing way wayyyy more! In my opinion it's a duff sensor somewhere, or leaking fuel/dead injector. I doubt a fuel injector cleaner would regain 200 miles back from a full tank.

That's shocking mpg.

Do you have VCDS? If so try logging group 3 and going for a drive. Include in the drive a wide open throttle run from 1500rpm to redline. And post the result here. Not read the full thread but might be a dogy sensor. You can also log group 7 (I think ) this will log temps. Do this on a seperate drive. Also log group 4 while your at it

Jason, what groups would you say for logging injectors? Isn't their one for smoothing the idle across the injectors?

went to york today from huddersfield there and back it did 51.1 mpg.. soon as i get back on normal roads it went to 29. maybe its local driving what the problem is?

1.9 TDIs don't really like cold starts and short journeys. 29 MPG is what I have achieved about 3-5 miles into any journey from a cold morning start. If I'm ultra careful, I can achieve 35 over the same route.

 

What speed was your longer journey and what's the "usual" local journey, MPG plus miles?

My octy 2 1.9pd regularly shows 65+ mpg on the computer on my 35 mile commutes to work. Things that spring to mind that haven't already been mentioned would be an air leak somewhere - will cause massive over fuelling - check for excessive black smoke out the exhaust, then check all the intake air ducting, turbo boost hose, intercooler, and vac pipes. Also, sounds very much like your timing could be slightly out, I believe the cam shaft on these has bolts that allow for fractional adjustment to get the timing Bob on, and this being set correctly (or not) can have a big impact on mpg amongst other things. Has it had the timing belt changed recently?