I use my 2001 A4 as my daily/work/raining outside car, x5 pulls out of the garage when its sunny and afterwork/weekends ride. I dont like putting miles on my 4.8is but i wish i could drive it all the time without racking up miles lol. Am also 19.

Audi local doesnt get great mileage at all.. 19ish, summer with a/c on even worse, hwy i pull out 26- almost 29 depending if always driving/any traffic/speed.

Edit: also dont make the mistake of thinking a smaller engined car or smal engine with turbo will net you better mileage, depending on driving if local/hwy,
The bigger engined v6 may be alot better option even if lets say split of 50/50 driving..

The v6 esp with ac running will end up netting you most likely better mileage local then a smaller 4 or turbo 4 because you need to rev it out more, yeah on hwy you will get a little less with v6 then 4, but it will even out cause of better local, and hwy 4 will get lets say 28mpg vs 6 26mpg.

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2006 X5 4.8is Fully Loaded