Today we stopped by the Mercedes Benz dealership. Last time we were at the Mercedes dealership, we sat inside the GLK and were not impressed. The M class was six feet away, but for some reason, it was locked on the showroom floor. Carson was getting grouchy, and so we were out the door without looking at it any closer.

With prodding from Rus, we decided we needed to take a closer look at the M class, particularly the ML-350 BlueTec diesel. I've been a fan of diesel engines for some time (post about diesels from 2005, and another post about diesels from 2007), and the latest ones from the collective efforts of Audi, BMW, Mercedes-Benz and Volkswagen are clean, fuel-efficient and possess none of the hassles (glow plugs, dirty exhaust) of the diesels of yesteryear.

These "clean-diesels" accomplish the task with urea-injection, which means approximately every 15,000 miles or so, you need to have the urea topped off. A hassle? Not much more than the hassle of having your spark plugs replaced in a non-diesel engine, I'd say.

Anyway, we got into the M class and while it was substantially better than the cheap interior of the GLK, the interior room wasn't impressive considering what we'd gotten used to with the other marquees we'd sat in. It wouldn't have been so bad except the configuration we're looking to get, with rear-seat DVD entertainment, places the DVD screen right behind the shoulder level of the front seat. Or, right at the touch point for where a rear-facing baby seat would go, cutting available seating room by at least 2-3 inches.

Disappointed, we began to depart, but the salesperson (I've grown to appreciate the difference in the salespeople at Audi, BMW, Mercedes and Volvo dealerships compared to Toyota, Lexus, and Acura) suggested we take a look at the R-class.

If you're not familiar with the R-class, it's a cross between an SUV, a minivan, and a sport wagon. We didn't have time to drive it, but it's based on a car body, has interior seating and room like a minivan, and four doors (no sliding doors) like a regular car.

Its seating room is comparable to the Honda Odyssey, but it doesn't look boxy and boring like a minivan. The used one they had on the lot (they were sold out) was a 2007 with captain's chairs, and that meant that with Christine in one seat, me in the other, with 4-5 inches of knee room from the front seats which were also moved far back, Carson was walking around between us on the floor. There is probably some apartment in Tokyo that has less room than the back of the R-Class.

Unlike the Tribeca, the 3rd row seats have plenty of knee room when the second row seats are copiously adjusted. Headroom is a different story, but the 3rd row seats are not ornamental in any way on the R-class.

If you drive by an R-class, take a glance at the length of the rear door. It is gargantuan in size, which means you need to be careful swinging it open in a parking lot, but also means placing a baby into a car seat is not an issue. And as a car-based platform, it's easy for younger kids to step up onto the car (no running boards required).

In short, the R-Class has climbed to the top of our list of what we like, followed by the Toyota Highlander, the Lexus RX 350, the Acura MDX and the Subaru Tribeca. Our original favorite, the Volvo XC90 now trails in fifth place.

That is to say, this is the rank of the cars as we sat in them, as we explored their features, fit, and finish, on the dealer's lot.

Two other rankings need to be taken into account. First, how do these cars drive? And second, what are they going to cost to own? I don't have a specific budget of how much to spend. A car is an expense, not an investment, so the critical factor in the financial dimension is not "invoice price", but the expense to own/drive it. The cost spreadsheet basically looks at "at given point X, how much did I spend on car Y, and how much more is that than the value of the car?"

Of course, the price you pay for a car is only one part of the total cost of ownership. MPG, service intervals/costs (outside of included service), insurance, warranty duration and coverage all come into play. My spreadsheet, which looks at the picture two years out, takes most of these into account, but will need updating as I negotiate the final prices on these cars (after the test drives, should that eliminate any cars based on driving them).

The preliminary numbers I've gathered for five of the cars (all well-equipped) puts the Highlander Hybrid in first place. After two years of ownership, including all of the above expenses taken into account, the expense of owning the car is about three pizzas short of $6K. The Toyota Highlander (non-hybrid) is $1670 behind the Hybrid, followed by the Lexus RX 350 ($3593), the Mercedes R350 ($4640), and finally the Acura ($9299).

I couldn't include the Volvo or the Subaru since they didn't offer finance calculators online that would have made a fair comparison possible, but assuming their finance incentives are as good as the competition, they are essentially a couple hundred dollars behind the Highlander Hybrid. (The Subaru is cheapest to insure; the Volvo is the cheapest to maintain with free service intervals for maintenance, but the Highlander Hybrid squeaks ahead on fuel costs)

Finally, Rus commented about residual values. The X5 xDrive35d does have excellent residual values (58% after two years), but Christine and I found the X5 to be a bit too small (note the scalloped front seatbacks that eat into the room for a rear-facing carseat's headrest here). Since residual values are dependent on the trim, news articles about residual value often don't contain enough detail. Of the cars in my spreadsheet, the Lexus RX 350 has the best (66%), followed by a three way tie with the Highlander Hybrid, the Acura MDX, and the Mercedes Benz R-class (52%). Fifth is a two way tie with the Toyota Highlander (50%) and XC90. Seventh place falls to the Tribeca (46%).