M.P.G fluctuating

[Stu8]

Hi everyone,

On a run to work in pretty much the same weather at the same time of day my cars mpg difference is quite large. One day my car can make 41 mpg on the way to work in the morning and the following day at the same time, with the same traffic on the exact same route and diving pretty much similar (changing gear at about 2000 rpm) the car can hit 49 mpg's? This is with the climate control set at the same temp etc. In the past my temp gauge has stopped working during a journey then started working again. It hasn't done this for sometime though. Could this be anything to do with it? Sorry for long post.

Any help appreciated.

Stu

[Stu8]

I've read up about the coolant temp sender failing? Some of the symptoms include the temp gauge not working and poor fuel economy. Could this really make 8 mpg difference? Car struggles to average 40 mpg and I don't exactly floor it everywhere, alot of my journey to work is along the a40 in oxford with some stop start traffic. Would of thought I would average at least around 44 - 45 mpg on a tank. Used to have a Civic type R which calculated was averaging 34 mpg and that was using vtec a few times. Thought the Passat would be better than this, it's why I wanted it. Any help is grateful.

[Stu8]

Switched off my climate control, car has now gone from averaging 41-42 mpg's to 48 mpg's. On way to work yesterday car hit 55.3 mpg's, it has never done that before. Can the climate control really use that much extra fuel or is there a problem with mine?

Ta,

Stu.

[andy23961]

I drive the same 65 mile to work and 65 miles back home again. Like you, in pretty much the same conditions. I can average anywhere from 48MPG to my highest of 60.8. Strange thing is, my car's economy seems to be best at 75MPH! 90% of my driving is on the the A46 at a steady 65..I mean 60 (The limit!) I too am baffled by the difference. I will keep an eye on your thread to see if I can find out why. Being an Automatic shouldn't make a difference..I don't think.

[Panzerdriver]

The last week or so i have noticed my mpg all over the place, a best of 53 then last week not much more than 42 mpg.

I have posted before about my own mpg and miles per tank and i have had pretty consistant results ie high 40's and 560 plus miles out of a tank with a combination of motorway and A road driving.

I did 136 miles to Gatwick from Peterborough on mon with speeds at the limit and a bit more and got a max of 44 mpg :zx11: which is rubbish.
Drove home this morning after nightshift same distance but from Gatwick to Pboro and averaged 48 mpg which was much better :D and this was with some stop start driving as well so what gives. Temp wise going down on mon 10c and this morning 1c so a small difference there but not drastic.

My old 130 tdi sport Passat with 133k on the clock would easily achieve 50 mpg and a best of 63 mpg.

My current 130 tdi sport with 75k does perform better but the economy is nowhere as good. I think its time it had a visit to VW under warranty to see if anything is amiss. The car is serviced according to schedule all pipe work is sound fluid levels tyre pressures etc all correct, checked the brakes for binding, nothing hanging off the car and no fault codes. I do leave my climate control set to auto but did try it in manual but no difference.

One of the lads i work with has identical car with 25k on the clock and his mileage is in the 50's with a best of 61 mpg and he does not drive like a saint either. (He does 35 miles each way but on A roads most at national speed limit with a final short blast on the M23)

3 different cars with different mileage all 3 driven pretty much the same so nothing really sticks out.

Just as a footnote to the above my fuel warning light came on with 545 miles on a tankful with an indicated 45 miles worth of fuel left in the tank so it would appear things are not bad just some days are bad but why, same speeds same traffic etc. :aargh4:

[Stu8]

This is a strange one, in the early hours of Friday morning picking my girlfriend up from work at 3 AM I averaged 41.7 mpg, this was 3 in the morning remember with no traffic, all dual carrigeway and a steady 40 mph drive along a 2 mile straight road into Oxford....Following day at 7:30 PM in the evening, the exact same journey as mentioned above....with stop start traffic and I managed 48.4 mpg?! Sometimes the car feels very lively like I would expect it to, other times it feels sluggish almost like i'm driving on flat tyre's. If it was AMM failure would it do this or would the AMM fail completely and give me rubbish mpg's all the time? Any help is appreciated.

[Panzerdriver]

Well took my car to my local dealership under warranty regarding fuel consumption and my slightly erratic water temp gauge.

End result changed the water temp sensor read for any fault codes (no findings) as was told the temp sensor would be the cause of my fuel consumption problems. OH REALLY!!! was it hell, its still crap. If i drive like a monk then i can get 51 mpg which most people would be happy with but i dont drive like a monk.

I do expect to get 48+ mpg on a run at legal speed levels not 42 to 43 so not a happy camper. Any ideas to potential faults would be gratefully received.

[Stu8]

Better news regarding the consumption, on a run to worcester car averaged 60.3 mpg's. On the way back to Oxford later that day at one point the car hit 62.7 mpg's. Guess i'll just leave it no point changing anything like AMM with mpg's going so well.

[Panzerdriver]

Must be something in the air as my bomber managed 51.5 on the run back from Heathrow today and that was with some serious right foot action.

[cazyp]

I think somedays you're wearing heavy shoes and somedays light ones!
CC makes a big difference as does windows open/roof bars etc etc.

[Panzerdriver]

I understand where you are coming from but from a personal point of view i monitored my cars mpg over several weeks, different roads driving conditions etc and compared them with my previous car which was the same model and there was a large difference in fuel consumption between the two.

Now maybe as the car is getting a few miles under its belt its improving with age but the proof will be on mon evening when i go back to Gatwick.

My CC is always on (better to be left alone then messed with) no roof bars (unless the other half forces me to go to IKEA :aargh4:) and i always leave the windows up so the car is always in the same configuration. Same shoes as well!!

I personally feel that its going to be one of those cars it may mellow with mileage but if not it will go in 2 years time.