I’ve owned my 2005 VW Jetta TDI (Turbo Direct-Injected) diesel for nearly four years. I bought it because I wanted a car that was economical to operate (I drive a lot) and I wanted a car that would last (I don’t buy new cars on a whim). On both counts, I couldn’t be happier.

Here is a summary of my costs for these past 45 months (95,000 miles):

Fuel: 5.8 cents per mile (average mile per gallon: 42.1; assumed price of diesel-today’s prices: $2.50/gal). On average, diesel fuel costs 10 to 15 percent more than regular unleaded gasoline.

Maintenance: 6.0 cents per mile.

Ownership: 9.7 cents per mile (based on the difference between what I paid and what the car is worth now, divided by miles driven).

Total cost: 21.5 cents per mile.

I paid $27,000 for my car in July 2005, including every option available; it’s a compact lux-mobile. A basic Jetta TDI with automatic would have cost $24,000. An identical 2009 Jetta TDI automatic sells for the same $24,000, with a new cleaner diesel that generates 50 percent more horsepower and produces better fuel economy. At the moment, you can get a $1,300 federal tax credit for 2009 for buying a Jetta diesel. The credit will expire after 60,000 Jetta TDIs are sold (a threshold already reached by the Toyota Prius, so no federal tax credit is currently available for Priuses).

According to the Kelley Blue Book, my car is now worth $17,815. With a gas engine, it would be worth $5,150 less. So the $1,200 premium for the diesel engine was a sound investment. With a gas engine, my ownership cost would be 13.8 cents per mile, instead of 9.7 cents.

With a gas engine, my fuel costs would be 8 cents per mile instead of 6 cents, assuming I averaged 28 mpg with the gas engine. Maintenance costs would be comparable. But over the long run, my diesel engine will cost much less to maintain, because diesel engines are much more durable than gasoline engines.

But there are quirks to owning a diesel. They don’t start instantly when the engine is cold, except on warm days. “Glow plugs,” rather than spark plugs, are used to ignite fuel in the cylinders; once the engine is running, heat generated by fuel compression ignites the fuel. During our winters, glow plugs need 3 to 5 seconds to heat up.

To avoid a puff of black smoke, you can’t make jackrabbit starts. Acceleration tends to be slower than with a gas engine, but passing power at highway speeds is comparable, because diesels have a higher torque-to-horsepower ratio. Diesel engines are low-revving; at 60 mph, my RPMs read 1,600 (would be about 2,000 with a gas engine) – a principal reason why diesel engines last longer, another being the inherent lubricating characteristics of diesel fuel (which is, after all, an oil).

For many people, using biodiesel is the best reason to drive a diesel. Some day I’ll make the few fuel-handling changes that may be needed to use biodiesel exclusively: different fuel lines, perhaps a heater to pre-warm the biodiesel (which tends to gel in very cold weather).

For now, I’m content with the occasional tank of 5 percent to 20 percent biodiesel, which is entirely non-Middle-East-grown and more free of pollutants than hydrocarbon diesel; biodiesel also is less polluting than gasoline, except for nitrogen oxides – which can be condensed into on-board canisters for later safe disposal.

Biodiesel fuel is still rather expensive, in part because its production costs are not as highly subsidized as those of other fuels, especially ethanol. As our economy becomes “greener” and more biodiesel is demanded and produced, its comparative cost will fall.

So do I like my diesel? Isn’t that obvious? Would I buy another Jetta TDI? Certainly, but for now, mine has too many miles left in it. Talk to me in another four years. Maybe eight. Or 12.