hello all,
i have a 1995 a6, i have been trying to figure out why i am getting bad gas mileage, ive checked all the obvious things like air filter, and so on... all the stats say it should get somewhere around 18 to 25 mpg yet i only get 15, 17 at best. a friend said something about running a hotter thermostat can improve mpg from the hotter engine burning gas more efficiently, when i drive the temp guage never gets above 1/4, i was wondering if this could be a cause, also does anyone know more about this or if its true. i'd love to hear about this or other suggestions

 

Do you have the 2.8 motor? On my '95 90 2.8L, the temp guage goes up to " 90 " which is where it's supposed to be. I believe the t/s is rated at 89 deg. Celius, standard on most Audis. If yours isn't getting hot enough (do you get hot air from the heater? ) replace the t/s, you don't need it any hotter than the standard 89 C.

My Audi 90 weighs a little less than your A6, I have the 5 sp. manual with over 175K miles and still get 25mpg in city and 30-31 hwy.

Have you checked the plugs/ wires, emmisons system, is your Check Engine light on .. ? Your mileage sound quite low, unless you are hard on the gas pedal, do you drive at 75mph ?
I have my other Audi, 2001 A6, 2.8Q, 5sp Tip, in the city it gets 17-18 and get 25-26+ on the hwy.

 

yes it has the 2.8, from what you've said it sounds like the temp is right, i havent checked all the plugs, but i did take one out to look at it, seems to be running rich, my check engine light does come on after i drive for a little while, i suspected that is was o2 sensors so i changed them but the light keeps coming on, i think im gonna go to the mechanic and have him scan it because im outta ideas. i do drive 70 sometimes, i thought of this already but i drove pretty conservative on a tank of gas to test this and it only improved about 1.5 miles that was the 17 mpg i talked about, do you know what else the engine light could mean in '95 they are pretty basic, not as many sensors

 

have you checked tire inflation? under inflated tires will reduce milage. try some fuel injector cleaner, gumout regain. do you use synthetic oil? that may help a little. replace air & fuel filters.
what octane gas do you use?

 

All of the above suggestions by ' beefski ' are valid points... you said " seems to be running rich, my check engine light does come on after i drive for a little while, i suspected that is was o2 sensors " , IF it runs rich, you WILL burn lots of gas, and 17mpg at hwy speeds is Not good mileage for that engine. I think it's still running rich.

 

yea, fuel mixture is the best guess at this poing thanks for your help. i think im gonna go and get it scanned, ill post another reply to when i actually find out what is wrong

 

keep in mind also gas mileage is an estimate. they don't pay people to drive all day till they run out of gas and then average the miles out.

but if you have a CEL then you do probably have a legitimately problem.

its probably an O2 sensor code or a CAT efficiency code

 

i got my car back from the mechanic and it turns out that there were several thing the matter. for one a vacume hose to the throttle was broken in two, also there was an air leak in the throttle which they sealed, the gas problem was most likely the EGR valve he said it was all plugged with carbon which was one of the main codes on the CEL there were others including the o2 sensors because i didnt clear them. but now the problems fixed and its alot better my throttle response it way better.