lately ive been getting really bad gas mileage, about 12.5 mpg in the city. ive even been driving very conservatively, shifting early, keeping my air pressure right, putting in 93 octane, and i only have 2,000 miles since my last oil change (fully synthetic). ive only gotten 116 miles on just a touch more than half a tank. i hear a slight tick tick tick when the car is running, as if it was knocking a little, but its very low. i dont know if that is normal. the only thing i can think of is maybe the spark plugs are going bad.
let m know if you have any ideas. thanks.

btw i have a 99 a6 quattro 2.8

 

i would start checking your plugs, wires, and your air filter. especially if you don't know when all of that was last changed.

i would also hook your car up to a obd2 code reader, and just see if you have any faults. it may not throw a CEL but you still could have some code's stored.

check if there are any and post back

 

if your plugs were bad, you'd be running rich. and your ECU would lean out the car wasting less gas.

TSB
From 01-05-04, June 9, 2005

Long Term Fuel Trim - System Too Rich

You need to check for stored faults

 

sounds more like something is creating drag on the drive train making it work harder