Just a point of discussion....
I was driving to work in my Hybrid today (but this relates to the i30 in the same way) and I was calculating how much I save in a year by driving carefully.. By my calculations not that much!
I think the difference in economy between driving normally, compared with driving carefully in my Hybrid (or say a 1.6 CRDi i30) is only about .5 LPH.
This equates to 5 litres per 1000 KMs or 100 litres for 20,000kms (12 months driving for me at the moment) That equates to about A$140 P.A. at current fuel prices or less than $3 per week

Not saying I will (or could) stop being an economical driver but an interesting exercise all the same...
I think it would probably be a bigger difference the less economical your car was..
