A couple of months ago, I wrote about the 2010 Jaguar XF and praised its combination of luxury and performance.

Now, I just think it's OK. I should have driven the XFR before I started talking about performance.

This car bolts like lightening while keeping the same luxurious demeanor as its sibling that lacks an R at the end of its name.

The power numbers alone are impressive: 5-liter supercharged V-8, 510 horsepower, 461 pound-feet of torque -- more than a 20 percent jump in power over the 4.2-liter supercharged outgoing engine. Those are the kind of numbers that spawn even better figures:

• 4.7 seconds 0-60 mph time

• 63.7 horsepower per cylinder

• 1.9 seconds 50-70 mph time

• 155 mph top speed (electronically limited)

This is the drive-by-the-seat-of-your-pants kind of power that makes you laugh out loud in awe as you push through a big sweeper or mash the accelerator as you enter the highway. It grabs you and squeezes you like a powerful handshake that leaves a good impression. Then you do it again. You do it because the XFR rewards you every time.

Even the braking feels strong and stable despite the XFR weighing more than 5,000 pounds.

It's more than the big engine under that long elegant hood that makes this car so special. It's greater than the sum of all of its sumptuous parts.

The silky six-speed automatic transmission effortlessly pushes through the gears -- though paddle shifters are mounted on the steering column in case you want to play with them. The XFR also features an Adaptive Dynamics and Active Differential Control to level out the road. The systems electronically control the vehicle's dampening and rear differential almost instantaneously to make it an incredibly smooth ride. Drive through a big corner and the car's body remains almost perfectly flat. The only movement you feel is yourself sliding up against the nicely bolstered leather seat.

Even with the impressive power numbers, the XFR still gets 21 miles per gallon on the highway, though I don't imagine people buying this vehicle are terribly worried about stretching out every drop of premium gasoline. Then again, they probably didn't have $85,300 laying around to buy the XFR by wasting money.

For the discerning eye, there are a few changes to the body, such as reworked bumpers and lower front air intakes.

There are also louvers on the hood (for the supercharger) and special 20-inch wheels. The overall look is one of power and sophistication. It can cause people to stop dead in their tracks as they cross a parking lot, just to take a longer look at the XFR.

Its brawn moves all the way from its Bi-Xenon headlights that turn with the car's steering wheel to the four tailpipes.

When you sit behind the wheel, you can feel all of the power surging through the XFR. It's satisfying and confidence instilling. Driving along the road toward Ann Arbor, I could look out among my fellow highway drivers and know, without a doubt, that I am the fastest one out there.

I could pass anyone without thinking twice.

Oh, and I'm traveling in just a touch more style.

The interior does takes care of that. The leather and wood trim feels like it comes from a hand-built chest.

Like the XF, there are loads of interior amenities that make the XFR a luxury car. The JaguarDrive selector slowly pops up after a push of the start button. Jaguar calls the movement part of the car's "welcoming handshake." A sense of calmness overcomes you when you sit down in the soft leather seats, embroidered with a red R.

Luxury trappings can be found throughout the cabin. The touch screen navigation high in the center of the dash is easy to use and nicely lit (and easy to read whether driving at night or day with direct sunlight shining on it). The Jaguar Sense electronically opens the glove box or lights so it no longer requires a heavy hand.

Then there are high tech features, such as the radar-controlled blind spot detection. A small light comes on in the outside mirrors if something is in your blind spot. It takes about 10 minutes of driving to get used to this handy device. After using it once, you'll always want it.

Then there is the 440-watt Bowers & Wilkins stereo with 14 speakers that plays Green Day just as perfectly as Mozart. Take your pick.

The XF and XFR may have more similarities than differences, but it's utterly amazing to experience the difference that adding one letter can make.