So the abstemious Mini cost more to cover the distance than the petrol winner, the bigger Honda Insight drinking 4.635l/100km for a cost of $147.83, with the road user charge included in the per litre cost of the petrol.
The 2008 rally was won by a diesel, VW's Polo Bluemotion geared for cruising and drinking 3.64l/100km for a total cost, including RUC, of $130.83.
The first four cars were diesels, the fifth a Honda Civic hybrid averaging 4.765l/100km at $156.92 in total; not much more than the diesel's cost despite the fact it used over 18 litres more go-juice.
Clearly, small diesels use less fuel, which you'd think should be encouraged, not penalised.
Which brings us neatly to this week's drive - Suzuki's Swift diesel, at $25,990.
It fields a 1.3 litre engine in place of the petrol's 1.4, and with a modest 55kW at 4000rpm the 70kW petrol trounces it in power terms.
But the diesel's 190Nm at 1750rpm blasts the petrol's 130Nm at 4000rpm into the weeds, and gives this tiny car a mighty punch at round-town revs, a punch you can make the most of given the five-speed manual transmission and Swift's deservedly renowned sweet handling.
Sure, it's a smidgen heavier than the petrol car and that weight sits up front, slightly blunting this Swift's dynamic sparkle. But that's not what puts buyers off.
Suzuki claims 4.2l/100km thirst. I thrashed the throttle and recorded a 5.0l/100km average - still less than the manual petrol's 5.5l/100km claim. But paying $48 tax per 1000km - the levy for any vehicle under 3.5 tons - puts the per kilometre cost close enough that the private buyers and small businesses which would benefit from a more frugal car will only consider the petrol.
Suzuki NZ general manager of marketing, Tom Peck, admits RUC means Swift diesel buyers won't save money, but the car is selling - to fleets and government departments with a diesel-only policy.