Mk4 GT TDI 115 - loosing economy, ideas needed!!!

[Rob Crutch]

I'm hoping someone might be able to shed a little light on my troublesome car! I bought my Golf last September, it's my 17th VW and by far the worst (most problematic) I've ever had. I bought it with 116k and at the time it would give a good 60+ mpg on my 80 mile commute to work (160 mile round trip), I even managed an indicated 67mpg one day Anyhoo, the car is now showing 125,500 miles and over the last 3k or so I've noticed a steady decline in the mpg I'm getting, more so the car takes ages to reach 40mpg, and seemingly an eternity to get to 50mpg.

Does anyone know what would see such a reduction in MPG? The car was meant to have been serviced prior to me picking it up (the oil was clean), but I have no record of whether the diesel filter would have been cleaned - would that have any effect?

Thanks in advance,

Rob

[theboss]

I've noticed something fairly similar with a TDI 115 we have in the household... 55mpg used to be routine and expected and I even specifically recall getting >50mpg on several sustained 90mph long distance runs which is phenomenal. By comparison it now seems hard to get above 45mpg on a long run even when driving it gently. My brother has a 130 and regularly gets the 60-67mpg figures you quoted. This is despite a very good standard of maintainence, even a new turbo recently, and fitment of Michelin energy savers (which made a big difference on my brothers golf).

Believe it not one thing I have done which makes a difference is to switch the mpg display off, I find I often surprise myself by reading better consumption at the end of the journey if I'm not paying attention to it, than if I'm continuously striving for maximum economy.

Also the season makes a difference, if you've only had the car since September, its routine (for me at least) for consumption to increase during the winter months due to longer warm-up times, often wet roads, etc.

[tescor]

Check your tyre pressures maybe? Mine dropped 5 mpg when they were lowish.

[Schtum]

I ran a GT TDI 115 for 8 years and 120K miles. The trip computer rarely moved from an average of 47 mpg and that was with the car remapped to a genuine 150 bhp for second 5 years and 60K miles of its life.

However, in cold weather, the fuel consumption increases quite significantly; so much so that on my usual 20 mile commute, I could arrive at the office with only 42 - 43 mpg showing on the display. I think the best figures I ever recorded were in the region of 53 mpg on long motorway trips. Interestingly, I think the car was more economical cruising at 80 mph rather than 70.

The other consideration would be if the performance has dropped off or it's erratic through the rev range, then it would be worth investigating the condition of the MAF sensor.

[Tame Technician]

We've have a few customers complaints about MPG in the last month.

Cold weather can rob you of 4 or 5 even more if you do a short trip and the engine doesnt full warm up.

Tyres pressures 2 or 3 but not a lot more than that I'd say.

Binding brakes can cause issues too.

Air filter and MAF sensor are favorites if it really droped off like 10-15 or so.

[Rob Crutch]

Tame Technician said:

We've have a few customers complaints about MPG in the last month.

Cold weather can rob you of 4 or 5 even more if you do a short trip and the engine doesnt full warm up.

Tyres pressures 2 or 3 but not a lot more than that I'd say.

Binding brakes can cause issues too.

Air filter and MAF sensor are favorites if it really droped off like 10-15 or so.

Cheers for the suggestions. The car itself feels very healthy, it's fairly recently had a head gasket done and came back feeling good, it was suggested to me by a local VW specialist that my MAF had gone which suprised me as I'd had a few go and it didn't feel like it had, but in an effort to make the car run better I've put one on to no real benefit. Tyre pressures will be double checked in the morning (snow permitting!), my handbrake seemed to stick a little this morning (maybe the because of the cold?) but was fine when I came home tonight so I'll put on that on the things to check list as well!

Thanks all!

Rob