Got a 316i, 186k miles, and ticking like a bitch.....
Have calculated it twice and I've got just over 45mpg out of the last Ԛ£20 I put in
And to think, I was impressed with averaging 40!
Trick is sticking it in 5th and keeping the speedo at about 32mph in town, as long as you only give the throttle a very light squeeze when you want to accelerate or go up slight hills (steeper hills will need a shift down to 4th or maybe 3rd, well in my car anyway

) - you don't want to be using anywhere near full throttle under about 1500rpm......