Since my wife is an art historian and museum curator, our typical holiday, even if we decide to spend it relaxing on the beach, invariably entails a series of hectic drives to some remote monastery or an esoteric art museum.

While driving in Spain, we used a total of 22 gallons to drive 1,000 miles, which comes to around 45 miles per gallon.

Meanwhile, the beach part of the vacation ends up shrinking to an hour or two here and there, mostly when museums tend to be taking a siesta.

A few years ago, we were in Puerto Rico on a weekend package trip — and even then, we rented a car in San Juan and crossed the island to visit an art museum in the city of Ponce (a very decent one, by the way, well worth a special visit).

With that in mind, I knew our two weeks in Spain were not going to be all fun and games and roasting in the sun. In fact, our long-suffering 14 year-old son Sam and I were both warned that we would have to range fairly widely from our base on Costa Brava just north of Barcelona, going as far north as Perpignan, France, and as far south as Valencia.

Determined to combine work and pleasure, I reserved an Alfa Romeo 159 from Avis. I love driving those nifty, stylish, sporty Italian automobiles.

They used to be available in the United States as recently as 1995, yet Alfa Romeo’s parent, Fiat, perennially postpones bringing them back. Now the date of its return to the U.S. market has been pushed back to 2011, even though Fiat's purchase of Chrysler may now make the new deadline stick.

A pedestrian Passat

Alas, as everyone knows, it is not so easy nowadays to get a vehicle you want from a rental agency. They give it to you only if they have it available, which is not often, and otherwise you have to settle on something less desirable in the same vehicle class.

In our case, instead of a sexy Alfa Romeo, we were offered a Volkswagen Passat, a good German car to be sure, but nothing to write home about. Ultimately, it is a staid, pedestrian everyman’s mode of transportation — especially when compared to something Italian.

Oil accounts for around half of the U.S. trade deficit — and, consequently, for half of all the new foreign debt that Washington keeps piling up.

Back in the States, very good friends of ours living in our suburban town drive a Passat. They mostly use it to go to the supermarket and to the train station, and they are very happy with it.

What distinguished the Passat we rented in Spain from theirs was a diesel engine. I had driven diesels before on my previous trips to Europe, and I knew that they offered a considerable advantage in terms of fuel economy compared to the conventional gasoline engine. But nothing had prepared me for what I got.

Before I go on, I need to mention the issue of fuel prices. In Europe, prices at the pump are brutal. Still, it always shocks Americans to see how expensive gasoline and diesel really are on the other side of the Atlantic. Americans moaned and couldn’t believe their eyes last year when gas sold for $4 per gallon. Since then, gas prices have tumbled to around $2.50 per gallon as crude prices slipped from $140 per barrel to around $70 per barrel.

But not so in Spain. Gasoline still costs around €1.15-1.20 per liter, which translates to a cool $7 per gallon in terms of a sagging U.S. dollar. Diesel is cheaper, but not by much. A liter costs around €1, still a considerable chunk of change.

Eye-popping mileage

When I got behind the wheel of my new Passat, I noticed a digital display on the dashboard which showed kilometers per liter, liters per 100 kilometers, or some such thing to which I initially paid no attention.

But as we kept putting serious mileage on the car and the fuel gauge barely stirred, I decided to investigate. I got out a calculator and spent some time translating various figures into miles per gallon.

I did it repeatedly, each time coming up with something like 45 or even 50 miles per gallon. This seemed far too good to be true. I decided I must have made a mistake and gave up.

In the United States, we would have spent less on fuel, only around $90, but we would have used 37 gallons of gas versus 22 gallons of diesel — or fully two-thirds more fuel.

But the fuel gauge continued to crawl toward zero at an excruciatingly slow pace. Filling stations kept popping up on the side of the road, and we kept ignoring them — there simply was no need to fill up.

In the end, we drove 1,600 kilometers on highways and in towns, an equivalent to exactly 1,000 miles. We refilled our 18.5 gallon tank once when it finally got to empty, and then topped it up a quarter of a tank just before returning the car to the rental agency.

We used a total of 22 gallons to drive 1,000 miles, which comes to around 45 miles per gallon.

All in all, we spent roughly $130 on fuel. In the United States, where both regulators and motorists for some inexplicable reason resist the introduction of modern diesel engines, the same Passat gets 19 miles per gallon in city driving and 29 miles on the highway.

Our driving in Spain was mainly highway, so let’s take 27 miles per gallon as a reasonable average. In the United States, we would have spent less on fuel, only around $90, but we would have used 37 gallons of gas versus 22 gallons of diesel — or fully two-thirds more fuel.

In Europe, the overall fleet of cars on the road achieves around 40 miles per gallon. This compares to a feeble 27.5 miles per gallon in the United States, based on the corporate average fleet efficiencies (CAFE). President Obama has called for an increase to 42 miles per gallon by 2016.

Note that the new Passat BlueMotion gets well over 60 miles per gallon on the highway. Not too shabby. At 60 miles per gallon, we would have used just 16 gallons — i.e., refueled only once, with room to spare in the tank — and spent about as much as we did on cheap U.S. gasoline.

It always shocks Americans to see how expensive gasoline and diesel really are on the other side of the Atlantic.

The question is whether it is really worth it for the United States to import two-thirds more oil from places like the Middle East, Russia and Venezuela for the dubious pleasure of driving gasoline engines.

Oil imports to the United States average $20 billion per month, or $240 billion annually. Oil accounts for around half of the U.S. trade deficit — and, consequently, for half of all the new foreign debt that Washington keeps piling up.