When I bought my 2006 AWD S80 in July, the average mpg reading was 21. Today I reset the odometer and after 30 miles the reading is 15 and going down during town driving.

Is anything wrong with the car??

 

Probably not. Before it had hundreds of miles of data to take in account for the average. Now that you reset it, it's only got those 30 miles of stop and go driving.

 

x2. Mine is amazing just after I reset it, but it slowly goes down after a few warmup periods.

 

Yep, the computer defaults to factory maps and the average MPG set at the factory It needs some driving to re learn.

Regards, Andrew.

 

star**

 

Over the weekend, I drove highway only and got 31.6 mpg by dividing mileage by gallons used. The result was a mileage of 31.6 mpg. The mileage odometer average mpg read 21.5.

Why the difference? I reset the odometer at the start.

 

Because it counts all of your driving, not just highway and city. The car isn't going to know when your driving what. So now you have highway miles and city miles, that's why it's up from 15 when you were in the city.