mpg for 1999 A6 Quattro 2.5tdi tiptronic

[Rob Morgan]

Hi

I have recently bought a new (to me, anyway) A6
I used to own a 2.8 A4 quattro, which did around 20mpg. My new A6, which i know is a lot heavier, has managed 22mpg over 2 weeks. This is based on the trip computer. In approx 2 weeks, when the tank shoud be almost empty i will work out an actual mpg.
In the mean time, what are you all getting?
I drive around 10 mies to work, 5 days a week, and then a bit of running around the other times.
1 journey to work, displayed 24mpg.

I must(not) confess, that i am used to driving cars with induction kits & sports exhausts, so i usually drive to the sound of the engine. However, the A6 tdi, is so quiet! i reguarly find my speed accidently creeping up, which cant be helping too much.

As far as i am aware, the car has not been remapped. This is something i fancy doing though. Can someone tell me roughly how much the mpg woud raise by? Ideally, i was expecting it to return 30mpg. Can this be done with y usual comute?

Thanks
Rob

[kid-jensen]

Does sound a bit low, but only the old-fashioned method of MPG checking can be relied on, so you will soon have the correct figure.

My diesel Allroad used to get about 28mpg on similar journeys, not driven partuicularly hard. I would really struggle to get it much above 32mpg though, even driving like a pregnant vicar on a long journey.

Yes, I know the Allroad is heavier... I'm assuming you have a tiptronic?

[adamss24]

Does the water temp. gauge needle stays bang on in the middle ? The 2.5 suffer from duff thermostats, viscous fans and worn camshafts, when they fail the engine overfuels to get the engine warm. Also could be worn nozzles, i swapped nozzles in my allroad tdi with larger Bosio power plus 683 nozzles and fuel economy went up by over 1.5L per 100Km, i can do 35Mpg nicely in my manual allroad fitted with 20" rims ! Also my 300Bhp 2.5 tdi a6 quattro does still return 32Mpg average regardless of how i drive it !

[Rob Morgan]

Hi, thanks for the info. yes, mine is a tiptronic.
i have noticed that my temp gauge takes AGES to get up to temperature. My old 2.8 A4 did too, this time of year though. My solution in my old audi, was to block off the radiator a bit. but with my tdi, the intercooler gets blocked as well, so i thought that was a bad idea? i have very little official service history with the car.
the cams runs quietly, and they do not look warn when looking through the oil filler cap.
what has the viscous fan got to do with mpg?
is the thermostat an easy/cheap fix? i usually buy a haynes manual for every car i own, but it turns out that they do not do one for the 2.5tdi A6!!!!

adamss - did you mean 1.5L per 100km? i've never heard of that before, but google tell me that 1.5Gallon per 100km = 41mpg

i wanted to get my car running 100% (or close as i could to it, lol) before getting it remapped

[kid-jensen]

Think you might have pointed to the problem(s)..

If it's taking ages to warm up the most likely couse is a stuck-open thermostat. Because it's so expensive/PITA to replace, it's worth eliminating the viscous fan. If it's siezed (it happens) you will be blowing the cooling systwem cold all the time. This shouldnt affect warmup time too badly IF THE THERMOSTAT IS WORKING, but will make things much worse if it's not. It will also take it's toll on the MPG, and make a bloody row....

Do the famous "carrot test" to establish if it's siezed.

If you have the viscous unit freewheeling (also happens), it wouldn't explain your problem, but needs to be fixed anyway, certainly before the warm weather comes back (no urgency, then)

[Rob Morgan]

carrot test???
a thermostst is £10 at eurocarprts so it not expensive. or am i missing something here???

[adamss24]

If you do the work yourself then by all means- you can use a cheap thermostat- i have used them and with good results, however i would always use a genuine stat if you pay someone to change it !

[kid-jensen]

Second the view about genuine thermostats. It's such a lot of work to get to, you wouldn't want to do it too often, unless you need an excuuse to get away from the wife for long periods of time. Somewhere on the forum, there must be a DIY for Thermostat replacememnt, worth a search anyway. Because so much has to be taken off to get to it, it's definately worth replacing the other bits in the area that are prone to failure, certainly the Timing belt (unless you have guaranteed evidence that it's been replaced in the last year or so) and even the water pump as they're not too expensive (well, not to expensive in Audi terms). The carot test is all about establishing if the viscous coupling varies its viscosity when it should. When cold, you should be able to stop the fan with a carrot, when hot, it will get a good slicing. That's how they work, the engine only needs cooling when it's hot (doh!) so spinning the fan when cold just wastes fuel (3-5%), so may becontributing to your problems. If the carrot can stop the fan when it's hot, the fluid has leaked-out so the fan is doing nothing but using-up precious space unbder the bonnet.. Another big bill soon follows, though I've salways taken the opportunity to convert to an electric fan at this point.

[NickPicks]

carrot test???

While the engine is running, but cold, use a carrot to stop the cooling fan. If the viscous coupling is siezed, the fan will chop the end off of the carrot.

Some say real men use their fingers, but they learn better the first time they get a siezed one. Some people use a screwdriver, but then if it's siezed, it'll break the fan blades.

[Rob Morgan]

my fan was going quite quick earlier. however, my kitchen does not currently contain a carrot!
after my 12 mile journey to work this morning, the temp gauge had hardly moved!!!! how do i fix the fan, if it is that?