Can a good tune-up help my MPG?

[TheRam]

I have a very low milage M40 316i auto and get about 25 MPG on a mixed cycle (half motorway a bit of A road and the rest round town).
It's not long had a major service with all fluids and belts changed.

I think i need to change the hoses as I can smell fuel when using the heater fan from a cold start. Is this the reason for poor fuel performance?

Do you think tuning the car to run a bit leaner could help the MPG? Would that effect anything else adversely?

Sorry if i'm not making sense but I'm sure my car can do better on mpg then it is at the minute.

Thanks

Kit

[Morat]

A smell of fuel is often a sign of a fuel leak, this will definitely affect your MPG!
Check out the fuel lines under the bonnet, and also the check if you get a splash of fuel by the rear wheel when you brim the tank.