i've had a 1.9tdi 130 comfort since april and am very pleased with it - i do a daily 40 mile each way commute to work and up until dec regularly got mid 50's in mpg when taking it easy - mid dec 3 things happened to car at roughly the same time and since then i've struggled to get mid 40's mpg altho it still runs well

1. dealer oil service and check over

2. 4 new tyres fitted - previously on well worn michelin primacy sport but changed to goodyear eagle as much better deal

3. ran through deepish water on road and damaged plastic pan under engine etc which was hanging off - tyre dealer couldnt reattach when on ramp so removed most of it altho the rear section is still there

would any or all of these things cause drop in mpg of 20%?

worth taking it to tuning specialist for look over?

thanks

I kept a record of mine from new: same engine 1.9TDi PD 130. Tyres rotated ever 6000 miles.

each 3333 miles :

0-30K 38.7mpg 40.7 45.6 50.2 51.8 54.2 54.5 48.7 ( France ) 55.0

30K -53.3K 53.6 55.5 57.3 59.2 59.6 59.7 61.7

( tyres bold, Michelin Primacy all 4 down to 1.6mm, changed to Avon ZV3 at 54000 miles)

56.6K - 80K 55.9 53.2 52.8 53.2 51.7 52.2 51.3 54.1

So best mpg was running on just legal Michelin Primacys. Not quite as clear cut as a new tyre goes further per rotation and different tyre although marked as 225/45/17 or 205/55/16 will be slightly bigger or smaller. So the lower mpg is partly due to higher rolling resistance, partly due to actually driving further per mile your odometer reads !

One other thing to watch is the tyre fitters tend to think everything should be 26psi ( too lazy I think to look it up or ask how you drive ). I keep mine at 34psi (all 4 ) due to mainly motorway driving. Look in the filler cap it will give a table of pressures versus speeds and loads ( people or luggage ). An extra 2 psi can make 3-4 mpg difference on the motorway if taking it steady ( 70-75 mph )

As for the engine pan. From what you describe it must be acting as a giant scoop for the air that goes under the front bumper. This will not help. If it is the same as the Passat ( Anyone know ????? ) I would have thought 5-10 quid should get one from a scrappy. ( Have you dared to ask the Stealer what they want for a new one ? )

A service should not effect the mpg ( after all they will have cleaned out the air filter housing, checked the emissions are still in tune, checked the injectors are not overinjecting as they wear with age etc !!!! )

Was that a main dealer service ? Yes ! then forget what just written they just changed the oil and shone a torch at the brake pads

Just a thought. Have they overfilled the oil ? If so the engine will not run as well due to taking oil into the engine breather system. This will correct itself once you've 'burnt' the excess oil ( or you could drain some off - and you do not even need to remove the engine pan ! )

My car has consistently returned the same consumption - around 48mpg - on Continental SportsContact 2 tyres. One word of caution - the trip computer is very inaccurate. I measure the mpg by recoding the mileage and the amount to fill the tank when I refuel - this is the accurate way and gives me consistently 48mpgish.

The trip computer consistently claims 52-53mpg. Anyone else see this degree of error???

I'm afraid dealer servicing on these cars is a usually a joke and many important jobs are not done. In your case, I would without question check that a new air filter element has been fitted. The service book is a model of confusion in this respect, but if you look on page 14 there is a specific reference to changing this on Superb models only, at 2 years (if driven < 60k km). Needless to say, the dealer who supplied my car at 2 years old had not done this, and the air cleaner was choked.

The undertray on these cars is a lousy detail - they always seem to end up broken or missing (have a look at a few old Passats) due to very poor ground clearance and cowboy dealers who damage them. I had the same problem. Apart from noise reduction, the undertray is needed to maintain the correct engine operating temperature - economy will suffer if this is missing because the oil will be too cool. If you drive fast, there will be further aerodynamic losses if the undertray is missing and fuel consumption will be higher as a result.

As dear old VAG didn't put a hatch in the undertray to drain the engine oil (it's always sucked out via the dipstic tube in German garages) the trays always end up damaged by the "lads" at the dealers.

Fit a new tray, drive carefully and find a competent independent garage to do servicing work - or do it yourself.

rotodiesel.

Hi - I thought I would share the results of 3200 miles of mixed driving, comparing the indicated MPG over this period with calculations from diesel added and elapsed mileage. This is a 1.9 TDI 130 which is now coming up to 30K miles .

Over whole period I averaged a true 48.5 mpg with the trip computer telling me the average was 49.9 over same period . This is about a 3% over-read and I found the more local runaround mileage I was doing, the greater the difference between real and indicated average. I was not always filling up so could not do calcs on every addition of diesel.

I usually average low 40's. Got 52mpg once on a longer trip as I was stuck behind traffic. I have to really try to get in the high 40's - no idea how you lot seem to manage it! (PD130 manual).

I usually average low 40's. Got 52mpg once on a longer trip as I was stuck behind traffic. I have to really try to get in the high 40's - no idea how you lot seem to manage it! (PD130 manual).

Don't know if this is why but I use the cruise control whenever it is safe and practical to do so, especially on Motorways and A-roads. On the steeper inclines I don't try but wherever its possible/practical, I use the cruise. If all my driving was stop/start/local then I guess 44-45 ish would be the norm but I have frequent 600 mile round trips (every 2-3 weeks) to boost the average.