I went in for my 10k service a few weeks ago. Singe then My gas milage went from 25 mpg to 21 mpg. Any ideas why?

No I am still driveing the same. I even tryed to baby it for a tank.

 

did you check your tire pressure?

any update done to the ECU?

air filter replaced?

 

I don't know if they have the "summer blend" fuel down there but in areas of Georgia we have a special fuel blend (oxygenated fuel) when the weather warms up. It's suppose to reduce emissions. The end result (from what I've experienced over the last many years) is reduced gas mileage. It may be as simple as that.

 

Maybe it's hotter than normal, so you've been driving with the A/C?
Maybe you've started driving a lot of surface streets or stop/go traffic?
Maybe you've realized it's fun to jam on the gas because you bought an CAI recently?
Maybe your calculations or computer are wrong?
Maybe you've had more passengers than normal?
Maybe you got a late night visitor/son/daughter/relative taking your MINI out for a spin behind your back?

 

know i'm tapping in this conversation a little late...but I had the second service done and a similar thing happened to me. after 2 tanks all is back to normal. my situation may be a little different in that I also had a busted hose that was fixed, so perhaps it took a little extra time to 'acclimate' to my new/normal setup, but can't see it being that different.