Yep I get around 400 miles for a full tank before warning light pops on.
Linzi
If £1.40 is cost per litre then;
1 Gall = 4.54 Ltrs
£1.40 x 4.54 = £6.35 per gallon (yes it passed the £6 mark a while ago)
so for 30mpg;
30miles = £6.35 = 1 gallon
30mpg (30/4.54) = 6.61miles per litre
or
635/30 = 21pence per mile
Method of measuring
Fill tank to first 'click off' by pump nozzle (making sure it isnt just sitting wrong in filler tube)
Zero trip meter
Drive till warning light comes on (or until you reach a certain mileage)
Note mileage and fill again to first click off.
Note litres against mileage. (multiply litres by 4.54 to get gallons)
easy peasy