We just purchased this car-2000 A6, 4.2l V8. I've noticed two things that may have a relation to each other.
The oil temperature only reaches 170 degrees and that is after some time.
The gas mileage is horrific. I'm pulling 13-15mpg with some highway and being so ginger with the gas (which is hard to do in this car!).

The guy I bought it from said he changed the oil himself. My mechanic said the oil is good. pure synthetic but I don't know the viscosity. Maybe it is too thick?

We're in the NE, temps are around 30 degrees right now.

Question is: should this car run at the middle line 250 degrees constantly? Is it the colder oil that is messing with the mpg?

 

My car is a 2.7T, but your oil temp seems fine when you consider the ambient air temp is only in the 30 degree range. In town on cold days like that mine rarely get to 190 degrees. As far as the fuel mileage, these AWD Audis suck. This is worse in the winter because of the colder temps, the less economical fuel blend and is even worse if you're running on lower octane gas and doing a lot of city driving.

 

thanks, that helps. I kind of figured but with a 24/17 sticker, I thought i'd at least get in the 17-20 range despite the age of the car. oh, well. I am using 93 octane.

have a check engine light on, so I'll get that read right away and see if it's something that might be contributing. did have all the emissions checked out and it was just fine.

 

i have an '06 4.2. moderate climate I get 22-24 freeway and 15+ or so city. to me it sounds like your oil is too thick.

my '01 4.2 was about the same as my '03.

 

The oil should stay around 212F. It should not pass 250 or even be on 250 on regular driving.

In local driving the oil temp is usually <200F.

From what i read on BITOG thicker oil causes more load on the oil pump, and it creates more friction than thin oil so the oil temps on thicker oil is usually higher.

The oil you should use that is easily available is M1 0w-40 or new castrol 0w40, castrol 0w30. I would not use any 10w.

15 on mixed driving sounds normal. 15 on pure hwy is of concern. My 2.7 averages 17 on mixed driving. So yours having 2 more cylinders sounds about par.