Gary
Here is your example played out in black and white
2003
i) Assuming 0.62p per litre and 52 litres to fill up = cost of £32.24 per tank
ii) 50 miles per gallon would give you 11miles per litre so a full tank approx 572 miles
iii) Assuming a 2003 rate of 62p per mile and only half your miles paid
(A to B only) then you'd have been grossing £177.32 for every tank of fuel
less the cost of filling up (£32) would've given you
iv) £145 per tank
2013
i) 1.47 per litre and 52 litres to fill up = £76.44
ii) same
iii) @70pplm you would gross £200.20
iv) £123.76 per tank
That's £20 less per tank 2013 v 2003
or to put it another way using Gary's example
2003 £6000 in fuel = 9677 litres
@ 11 miles per litre=106,447 miles divide by 2 = 53,223.50 paid miles @ 0.62p = turnover of £32,998 minus fuel = £26,998
2013 53,223.50 paid miles @ 0.70p =£37,256 minus fuel (9677 x £1.47= £14,225) = £23,031
I'm not saying its good, i'm just showing what it means in black and white for those who want to see it