MPG
The trick is to get the accelleration over with in a reasonable time. You can spend 30 seconds at 15mpg or 90 at twenty. Deceleration is the exact opposite. It's better to let it coast down as far as possible even before applying regenerative braking, much less the old fashioned brakes. Put them on gently.

PAINTING
They can match it to where you can't tell it's been touched. It all depends on the skill of the shop. The one I use can match black to where you have to know it's been hit to find it.