NEW YORK — The 2008 BMW M6 convertible invites a swift departure from reality. It is an expensive escape pod bereft of practical value, generally lacking in common sense.

It can be enjoyed only through a willing suspension of disbelief, most often achievable with the assistance of wealth. Consider the price.

Without options, the M6 convertible starts at $106,100. (The phrase “without options” assumes knowledge that the M6 itself is an option.) Add-ons such as a heated steering wheel, black Merino leather seats, and an onboard navigation system can boost the price $4,000 or more. Standard equipment includes an additional $3,000 in federal gas-guzzler taxes.

That’s because the M6 gets considerably less than 22.5 miles per gallon on the highway, below which the government begins taxing cars for excess fuel consumption. It’s a simple formula — the poorer the fuel economy, the higher the tax.

The rear-wheel-drive M6 convertible, with its 5-liter, 500-horsepower, V-10 engine, sucks premium fuel at a rate that translates to 11 mpg in the city and 17 mpg on the highway, and it does that going at legally posted speeds.

At extra-legal speeds, the driver might as well knock a hole in the fuel tank, it drains so fast.

Anyone who knows anything about BMW should not be upset about any of this. BMW is a legendary performance car company, maker of the world’s “ultimate driving machines.” People don’t buy BMW for economy or fuel efficiency. They buy for power, speed and prestige. They want to make a statement.

I get it. But what bugs me about the M6 and other exotic cars is that the statement they make often amounts to a rolling contradiction. They are fast cars in a world slowly running out of the petroleum to propel them. The faster they go, the less they make sense.

The designers of the M6 are aware of this irony. The car can leap from 0 to 60 miles per hour in 4.5 seconds — even faster, according to some test-drive accounts. But it flashes a warning, dramatically displayed on the windshield via an optional head-up system, and sounds an alarm the moment the speedometer detects movement above 65 miles per hour.

“Speed Limit Exceeded,” the red warning message says. It is accompanied by a gold circle with the similarly colored word “LIMIT” written inside in all caps.

It’s a lawyer’s gimmick, implemented to give BMW plausible deniability in anticipation of someone somewhere having the gumption to accuse the company of encouraging reckless driving. It is the moral equivalent of the “drink responsibly” tag line usually found at the end of beer commercials.

You can always drink more, although you shouldn’t, especially if you are driving. In the M6, you certainly can go faster — putting its seven-speed transmission in either automatic or manual mode.

Manual mode is best. It has a higher fun factor. The car launches itself with giddy joy.

But it’s an expensive treat. Filling the M6’s 18.5-gallon tank for the 300-mile drive here from Virginia cost $93.

It was a fun romp, enjoyed without the unpleasantness of another speeding ticket. But I found my thrill and had my fill. With apologies to musician Fats Domino, a fellow New Orleans native, I’m ready to abandon the fantasy of this particular Blueberry Hill and journey back home at a more moderate pace.

The M6 is a wild car. But in the future, if BMW or any other car company wants to impress me, show me one that goes from 0 to 60 miles per hour in four seconds and gets 60 miles per gallon. I’d take it without leather seats.

The bottom line

Complaint: The BMW M6 convertible and its sibling hardtop M6 coupe represent grand motorized excess.

Ride, handling, acceleration: The M6 offers indisputably superior performance in all three categories. But your gas money evaporates in tandem with the car’s speed.

Head-turning quotient: I drove the M6 on Wall Street post-bailout. The car drew longing glances. One gray-suited man looked at the car. I swear he was crying.

Capacities: There is comfortable seating for two people up front in the M6, which is available as a power-operated softtop or hardtop coupe. The two rear seats are for tiny people on short trips. Cargo capacity is 12 cubic feet. The fuel tank holds 18.5 gallons of required premium unleaded gasoline.

Mileage: This one makes some sport utility vehicles look good. It gets 17 miles per gallon on the highway — barely.

Safety: Standard equipment includes four-wheel disc brakes with antilock protection, electronic stability and traction control, side air bags, and active head restraints designed to reduce neck injuries in rear-end collisions.

Purse-strings note: The M6 is a wonderful toy. But it should be sold with an oil well.

2008 BMW M6

Base price: $106,100 (at this writing — the caveat is that the base price has been rising)

As tested: $117,420

Type: Front-engine, rear-wheel-drive luxury performance convertible

Engine: 5-liter, 40-valve V-10, mated to seven-speed transmission

Mileage: 11 mpg city, 17 mpg highway