you cannot beat the economy of a diesel engine, I have driven many diesels, still drive one.. and their mileage cannot be beat.
Nissan Sunny 1.7 avg 20-22 km/lit
Nissan Sunny 2.0 avg 15-18 km/lit
Corolla 2.0 avg 14-17 km/lit
VW 1.6 avg 22-24 km/lit
mercedes benz 3.0 12-15 km/lit
All are not light foot driving and they can haul heavy load too.
Maintenance of the fuel filter is done very 15000 kms (meaning every 3rd oil change) - costs cheap as chips. I hate it when people compare their little silly kei cars with medium sized sedans, How about you load your kei car with luggage and 5 passengers, run it full A/C and climb nathia gali - It wont do it - it might once, but then you would have to pay mechanic for repairs.
What I believe everyone wants is a CD70 engine in a car..