Inaccurate trip computer?

[SteadyFreddy]

I've a new 200hbp petrol Passat and after about 3,000 miles brought it into the garage to check the mpg. At around 35-37mpg showing on the trip display and never getting above 39mpg I thought I'd never get to the magical 44mpg claimed in the brochure! It also seemed worse than my old 1.8T which regularly showed 40-42mpg - I didn't think that 6 gears and fancy FSI technology had bought me anything (OK, so I do get another 200cc and 50 bhp, but the brochure shows the 200bhp FSI to be slightly better mpg than the old 1.8T petrol - I was expecting it to be the same, if not slightly better!)

Sir, they said, we've upgraded the engine s/w and that included a fix to improve the mpg. I was impressed to see it now display 40-42mpg regularly and up to 43 on rare occasions..........................the BAD news is that my average mpg based on measuring tankfuls before the upgrade was 35mpg, and after the upgrade, yep, still 35mpg!!! The upgrade to my software has increased the trip display by about 5mpg, but done nothing for the actual mpg (although I accept my measurements are not scientific!).

So, as a matter of fact, does anyone know how accurate these trip computers are? I'd assumed they were capable of very accurate measurement, not least because they show one decimal place.

And, more importantly, does any one know as a matter of fact, by how much VW engineers can 'modify' the display?

Gee, I should never have trusted anything to do with computers :Blush2:

[james_tiger_woo]

I think there's about a 8-10% discrepency in this - when I go from full tank to full tank (which is all the time), the trip computer may say that it's been 50/51mpg, but in reality it might be 46/48.

I use an excel spreadsheet to track my mpg so as to get more realistic mpg figures - the trip computer is used more as a guide.

[SteadyFreddy]

Thanks, that's useful to know you too get a similar margin of error. I guess I've learnt (and I'm old enough to know better!) that trip computers are only a 'vague' guide as to the actual mpg. Measuring tankfuls yourself is probably a lot more accurate..............

I think the issue is worse because the garage led me to believe the actual mpg had improved whereas they/VW had only improved the trip display, lulling me into a false sense of security! I was told by a VW engineer that there was a lot of adjustment in the trip display and that they could set them to what ever the customer wanted. I was also told that there was no definitive and absolute measurement against which the trip computer could be benchmarked.

Have I, no, are we being conned here?

[Stuart W]

I usually work mine out at intervals of 2-3,000 miles, and the trip computer has always been optimistic by 1-2 mpg, but never outside these figures, so it's certainly consistent, and clearly a bit more accurate than Steady's and James's.

However, I'm usually returning a real figure of around 40 mpg, thus I don't know if it would be less accurate if I was getting better consumption like James.

[Mav2006]

I also have the 200 BHP passat. I tend to use the onboard computer for guidance only, wouldn't rely on it.

[mluton]

You can change the setting via a VAG COM. Some one on here did it last week.

If you know how much its out by, say 15%, then you can change the value from 100 to 115.

[james_tiger_woo]

I haven given up relying on anything computerised TBH** - I use my trip computer as a guide and I try to keep the MPG as high as possible which is as good a guide as any.

**Bizarrely enough, I'm a Microsoft :firedevil: IT consultant :D:D

[Quatrelle]

I haven given up relying on anything computerised TBH** - I use my trip computer as a guide and I try to keep the MPG as high as possible which is as good a guide as any.

**Bizarrely enough, I'm a Microsoft :firedevil: IT consultant :D:D
Now that is bizarre :p;)

[mluton]

Here you go:
17 - Instruments - Adaption-10 - Ch No. 3 - Origininal val 100 (this is a %) my new value is 110. Use TEST and see Average MPG drop in DIS!

From this thread:
http://www.vwaudiforum.co.uk/forum/showthread.php?t=15119

[SteadyFreddy]

I also have the 200 BHP passat. I tend to use the onboard computer for guidance only, wouldn't rely on it.

Mav2006, hi I'm real interested to know what your actual mpg is (measured by the tankful and not the trip ;)) and how you'd describe your driving style & type of driving terrain (mainly town, country,motorway)? Nothing personal, it just gives me an idea when comparing to my rate of 35mpg on average. For comparision I'm a light driver, driving mainly for smoothness and good mpg (only use the 200 horses when I need to:Blush:) and cover mainly low speed motorway driving during rush hour.

Also, do you have any type of clutch judder when moving off in 1st gear? Another one of my bug bears:( I know others have had problems with this (in Golf's too), but I just want to find one person with the same car as I have that does NOT have this problem - then I can confidently go to VW and say, you can make at least one car work how it's supposed to, please make mine the same ;)


Thanks,

SteadyFreddy

[Mav2006]

Mav2006, hi I'm real interested to know what your actual mpg is (measured by the tankful and not the trip ;)) and how you'd describe your driving style & type of driving terrain (mainly town, country,motorway)? Nothing personal, it just gives me an idea when comparing to my rate of 35mpg on average. For comparision I'm a light driver, driving mainly for smoothness and good mpg (only use the 200 horses when I need to:Blush:) and cover mainly low speed motorway driving during rush hour.

Also, do you have any type of clutch judder when moving off in 1st gear? Another one of my bug bears:( I know others have had problems with this (in Golf's too), but I just want to find one person with the same car as I have that does NOT have this problem - then I can confidently go to VW and say, you can make at least one car work how it's supposed to, please make mine the same ;)


Thanks,

SteadyFreddy

Hi SteadyFreddy

I have to confess I don't always calculate it manually, but when I do its a few MPG lower.
Commute of 40 miles a day - a fair bit stuck in traffic. Tend to drive it quite hard on the weekends, like to make use of the 200 horses. I think some people are surprised to see a Passat disappear in front of them. Overall I would guess the MPG is low 30s rising to mid to high on a decent run.

Maybe I'll pm you when I next get fuel...

With regard to the clutch, yes I do. It was quite bad until 5000 miles, I have put it down to the auto hand brake. Nice gadget but I'm not convinced about the benefits. Also have a query about wear on clutch? Also I have noticed in traffic that the clutch seems to squeal.

My wife has a Mk5 Golf and has no issues with the clutch on that.

Overall I'm happy with the Passat and Golf. I think good car for the money. Did consider a 3 series but found them a little small.

Feel free to ask anything else

Enjoy the driving!

[Mav2006]

Steady - -just re read your first post. I also had a 1.8t previously, use to get mid to high 30s according to computer.

[SteadyFreddy]

..............With regard to the clutch, yes I do. It was quite bad until 5000 miles, I have put it down to the auto hand brake. Nice gadget but I'm not convinced about the benefits. Also have a query about wear on clutch? Also I have noticed in traffic that the clutch seems to squeal....................

Mav2006, do you mean the clutch judder disappeared at 5,000 miles, or just improved to the point that it was still noticeable, but acceptable? It seems that mine is getting better (much to my relief) but how on earth can that be??? I was told by VW that my auto handbrake is fine so that was not the issue, nor would it have been loose engine mountings, as I had thought because that tends to give you a jolt whilst taking off and then another jolt as you ease off the gas. They were pretty convinced it was the flywheel/clutch and could not really be anything else.

Don't know about the expected clutch wear, but if your clutch was 'quite bad' and 'squealed' I'd be having it replaced under warranty at that mileage before they could claim it was down to normal 'wear and tear' and therefore not covered ;)

[Mav2006]

Mav2006, do you mean the clutch judder disappeared at 5,000 miles, or just improved to the point that it was still noticeable, but acceptable? It seems that mine is getting better (much to my relief) but how on earth can that be??? I was told by VW that my auto handbrake is fine so that was not the issue, nor would it have been loose engine mountings, as I had thought because that tends to give you a jolt whilst taking off and then another jolt as you ease off the gas. They were pretty convinced it was the flywheel/clutch and could not really be anything else.

Don't know about the expected clutch wear, but if your clutch was 'quite bad' and 'squealed' I'd be having it replaced under warranty at that mileage before they could claim it was down to normal 'wear and tear' and therefore not covered ;)

Steady - it improved greatly after 5k, have now done 12K I can live with it now.

Only squeals when doing start stop in traffic

[alogbe]

You can change the setting via a VAG COM.I don't have VAG COM. Is this something it would be reasonable to ask a dealer to do?

The consumption shown by my A6 is consistently understated by about 15% and I noticed the same thing on my previous car, an A4. I was beginning to think it was an Audi feature, programmed in to make you feel better.