Citroen C4: 7.1 vs 4.7 litres/100km (+$4000) Photo Gallery

So, you're alarmed at the price of fuel, especially the price of diesel which is going to hit $2 a litre long before petrol does.

A check of the NRMA's Petrol Watch website revealed the average price of petrol in Sydney this week was 164.1 cents a litre compared to diesel at 182.1 cents a litre 18c more.

The thing is, even at this price a diesel vehicle is still going to be cheaper to run, at least in terms of the amount of fuel consumed.

But most people only see the price and have difficulty grasping this fact.

We had a look at the 12 fuel savers this week in the booming small car segment, comprising two hybrids and 10 diesels.

We compared the fuel consumption of petrol models to that of the fuel-saving hybrid or diesel alternative, along with the difference in purchase price of the two.

Our comparison shows the average fuel consumption of the petrol model followed by that of the diesel or hybrid, with the extra cost of purchase for the fuel saver shown in brackets.

In the case of the Prius, which has no directly comparable model, we compared it to the most expensive Corolla, the Ultima sedan.

The cheapest of the fuel savers is Hyundai i30 CRDi at $21,490, with the most expensive by far and away Toyota's much-vaunted Prius hybrid at $37,400.

There's more to the story than just fuel economy as the initial cost of the car has to be taken into account as well as its resale value, which in the case of a diesel is going to be higher.

For example, take Hyundai's i30, a car that comes in 2.0-litre petrol and 1.6-litre turbo diesel form, both with a five-speed manual gearbox.

Both have a 53-litre tank but the petrol model uses 7.2 litres/100km compared to the diesel's 4.7 litres/100km.

That makes the cost of filling up the petrol car $86.97 and the diesel, $96.51 $9.54 more.

That's a significant difference and enough to put most people off.

But here's the thing.

Because the two cars consume fuel at a very different rate, the petrol model will, in fact, cost $11.81/100km to run, while the diesel one will set you back $8.55 a saving of $3.26/100km.

Taking this argument a step further, diesel would have to hit 252.1 cents a litre before the two cars would start costing the same to run.

Doubting Thomases will point to the difference in the cost of servicing the cars as well as the higher initial cost of buying a diesel vehicle.

My mechanic reckons there's very little difference in the cost of servicing the two.

But, in most cases, you'll certainly pay a premium of some kind for a hybrid or diesel vehicle at least $2500 more or, in the case of the Prius, $5410.

Using the i30 as an example again, the SX petrol model is priced from $18,990 while the same model with a diesel engine is $21,490 a difference of $2500.

With the cost of fuel at the current prices, that means you'd have to travel 76,000km before you'd recoup your initial outlay and start to reap the benefits of diesel's lower fuel consumption.

Therein lies the rub because, for the majority of people, that's about when they'd begin thinking about getting rid of their car and updating to a new model.

COMPARATIVE CONSUMPTION:

extra cost of purchase in brackets

Citroen C4: 7.1 vs 4.7 litres/100km (+$4000)

Dodge Caliber: 8.0 vs 6.1 litres/100km (+$4000)

Fiat Ritmo: 7.1 vs 5.6 litres/100km (+$3500)

Ford Focus: 7.1 vs 5.6 litres/100m (+$4000)

Holden Astra: 7.8 vs 6.0 litres/100km (+$3000)

Honda Civic: 7.2 vs 4.6 litres/100km (+$4000)

Hyundai i30: 7.2 vs 4.7 litres/100km (+$2500)

Mazda3: 8.6 vs 6.0 litres/100km (+$4000)

Peugeot 308: 6.7 vs 4.9 litres/100km (+$4000)

Renault Megane: 8.2 vs 5.8 litres/100km (+$3000)

Toyota Prius (Corolla): 7.7 vs 4.4 litres/100km (+$5410)

VW Golf: 7.5 vs 5.5 litres/100km (+$2500)