• I was worried about my wallet as I headed out on a 1500-mile weekend road trip in the Mercedes-Benz R500, what with gasoline hovering around $3 a gallon and with this R-Class powered by not by some fuel-sipping four-banger but by a big V8 engine. But I had miles to go and a brother to see, and the R500 turned out to be a pretty terrific road trip vehicle. And then there was that very pleasant surprise when I did the math and discovered mileage numbers much better than anyone might have anticipated.

Don't believe everything you read on a Monroney sheet.

I recently did a three-day, 1,436-mile drive in a 2006 Mercedes-Benz R500, and one aspect of the trip had us quite apprehensive. Well, it wasn't so much an aspect of the trip as it was the fact that just days before I was to depart Phoenix for Breckenridge, Colorado, the price of gasoline started hovering right around $3 a gallon, so the prospect of nearly 1500 miles had me wishing our test car of the week had about half as many thirsty cylinders as the R500 had under its hood.

The 5.0-liter, 306-horsepower V8 in what Mercedes calls a sport tourer is a wonderful engine, but if you look at the Monroney sticker, you discover that the Environmental Protection Agency says that even sending its power through a seven-speed automatic transmission, that engine returns only13 miles per gallon in the city and just 18 mpg on the highway.

Fortunately, I'd be doing my driving on highways. Unfortunately, most of those highways would involve some serious altitude, not to mention some pretty serious climbs - just going from the Valley of the Sun to Flagstaff involves several thousand feet in elevation gain, and in Colorado we'd have to tackle one mountain pass more than 10,800 feet above sea level and another that took us above 11,500 feet.

You want wonderful gas mileage, do you driving at sea level, not up in the stratosphere where the thinner air robs an engine of its power and makes it work harder (burn more fuel) as it tries to compensate for the lack of oxygen.

Worried about my wallet, I headed north on Interstate 17 to "Flag."

Tangent alert! Before the trip, I went to Mapquest to see just how far it was from Phoenix to Breckenridge. Way too far, the website reported.

When I looked at the route details, I realized the website's mapping service defaults to major highways and was directing me from Phoenix to Flag and then to Albuquerque, New Mexico on I-40 and then to Santa Fe on I-25 before heading north on US 285.

I think Interstates should be avoided whenever possible on such drives, and fortunately noticed the "Advanced Options" link so I clicked it and then the "Shortest Distance" button and cut like 200 miles from the trip and thus confirmed the route I'd planned to take in the first place: Phoenix to Flag to Tuba City to Four Corners to Cortez, Durango and Pagosa Springs, where we figured to spend the night.

Not only was it shorter, but even Mapquest said it would cut more than an hour from the drive.

Tangent alert 2! I got an uncharacteristically late start and it was getting dark by the time I reached Pagosa Springs. Tired and hungry, I - again uncharacteristically -- actually stopped at a chain motel. Fortunately, they had no more singles for the night, and the young woman working the desk suggested I drive six more miles to the other side of town, where her aunt worked, and where there was a steakhouse right across the parking lot.

It was wonderful advice, because the High Country Lodge is a wonderful facility with friendly hosts and the price of a room or cabin includes breakfast, and the Ol' Miners Steakhouse is quaint, intimate and serves wonderful food. I liked the Lodge and restaurant so much I stayed both nights I was in Colorado.

After a night's sleep and a hot breakfast, I headed up over Wolf Creek Pass and on toward Breckenridge, stopping briefly for a chat with a Colorado state trooper who gave me a warning for being 5-over the posted speed limit.

Tangent alert 3! I'm not sure what the deal was, but I've never seen speed limit enforcement like I did that Saturday in Colorado. Whether local police, marshals, sheriffs or state troopers, the roads were lined with red and blue light topped vehicles. In fact, one town that couldn't have been home to more than a couple hundred people had three cars clocking speeds on its main drag!

Anyway, I got to Breckenridge - not to ski but to pick up my brother, who had flown out from his home in Virginia with co-workers for a convention in Denver. While some of the party went skiing, my brother and I would drive down to Hartsel, to check out some land we'd inherited.

In many ways, the Mercedes R-Class is a terrific road trip vehicle. With its V8 engine, it's fast, but also surefooted with its full-time four-wheel drive. It's also roomy, whether you have people or cargo to carry.

After nearly 1500 miles, however, I also have some nits to pick.

First of all, you can't read the navigation screen or trip computer when wearing polarized sunglasses. And it's not just Mercedes. I find this in way too many vehicles.

Second nit: The door detents aren't detented enough. Again, this is a problem not just with this Mercedes, but with too many of the cars I drive. When I push the driver's door open, I expect it to stay open, not bounce back or have even a gentle breeze blow it back in my face.

Third nit: I found the headlamps barely adequate for driving after dark. This was a real surprise, especially from a German automaker that designs vehicles for driving on the autobahn at considerable rates of speed day or night.

On the other hand, my trip showed me one very positively surprising thing about the R-Class. I filled its fuel tank four times on the trip. While the trip computer indicated that I was averaging between 19 and 21 miles per gallon, when I did the math with actual mileage and fuel used figures, I actually averaged 22.6, 21.1, 23.9 and 23.1 miles per gallon, or basically four to five miles per gallon more than the Monroney sticker said to expect, and yet, as that Colorado state trooper can attest, I wasn't exactly babying the gas pedal.