Was helping a friend look for a suitable car and made up a spreadsheet which will calculate fuel and tax costs for different vehicles. For the Petrol vehicles I looked a fuel cost plus vehicle licensing per year and for the Diesel vehicles I looked at fuel cost, road user charges (a tax), plus vehicle licensing.
In NZ, diesel is currently $1.19/L while 91 petrol is $1.74/L (96, 98 and 105 octane are much higher but not needed in most of todays cars). Vehicle licensing is $421.81 for petrol vehicles and $548.85 for a diesel vehicle around the i30 size. Road user charges for a diesel vehicle up to 2 tonne is weight are currently $39.68 per 1000km (due to go up to $44.31 in October 2010).
Adding it all up, the diesel i30 manual is $4373.25 for 40,000 km per year (up to $4558.45 in October) while the 1.6 petrol manual is $4945.81. The 2.0 petrol is only available in auto and would be $5711.41 per year ( for 40,000km).
So nobody would really buy a diesel for the savings as they are not that great! Not for cars under 2 litres.
Biggest problem is the archaic road user charges where a fuel efficient diesel car pays the same tax as a 2 tonne, soot belching, 35 year old flatdeck which would use diesel at a staggering rate.
In NZ, there are only two models of i30s ... an entry level model which is essentially the Australian "SLX" and the "Elite" model which is the Australian "SR". Petrol manual is the entry level only and diesel manual is the "Elite" level only (2.0 petrol only "Elite" auto).
I am still very happy I chose the 1.6 cRDi manual as it is great to drive and I just like diesels. Have had them for over 20 years although there used to be a significant saving in running one. The current government has altered the tax so that there isn't the same benefit. Lower fuel usage to produce lower CO2 emmisions don't appear to factor in their thinking in promoting these vehicles. In fact, when the cost of petrol went over $2 a litre and the sale of Falcons and Commodores fell right off with an increase in the sale of small cars, the goverment mentioned taxing small vehicles at a higher rate to make up 'lost' taxes!!!!
I would say servicing costs are very similar as I will do all my own basic servicing when out of the warranty period. In fact, the 1.6 petrol may be a little more expensive at the mileage I do as to change a cambelt in NZ is between $600-800! Something I don't have to worry about with the 1.6 diesel.