Lets imagine you decide to drive from one end of the country the other. Devon to Yorkshire!
A good 800-1000 mile round trip. Thats what, even in the least economical car on a cruise about £100-£120 tops?
£25 each?
Seriously, is the saving really worth thinking about?! OMG the Corsa might cost you all £20 each! Its not worth it, is it?
Edit: What eidolon said.