You've gotta love the concept behind XCar: build and race the fastest prototype vehicle you can, period. Forget about all the rules for engine specs and other speed-draining dreamed up by racing organizations like NASCAR. In XCar, you can pretty much put whatever engine you like in your car and set it up however you want, and the only thing that matters is where you finish at the end of the race.
It sounds appealing, but the truth is that XCar is a very mixed bag - and how much you get out of it depends mainly on what you're looking for in a racing game. If you're deadly serious about car setup, XCar will have you drooling. The array of customizing options is, well, mind-boggling: Settings for engines, gear ratios, suspension, fuel type and quantity, brakes, wings, and tires can all be fine-tuned to suit the type of course you'll be driving on, and unlike some games that offer such options you actually can feel the difference after making changes to, say, tire pressure or camber.
An especially nice touch is the inclusion of three test tracks - a skid pad to test traction, a handling course, and an oval to check out what sort of top end you can expect. For the seriously hard-core racing fan, there's also telemetry data you can consult to find out stuff such as how many lateral G's you pulled in a curve - a bit overwhelming for the average race fan, but its inclusion is admirable just the same.
The eleven tracks included in XCar provide a nice variety of challenges and locales, from the flat-out speed of ovals (Red Rock Speedway) to the numerous 90-degree turns of city driving (Seattle). There are 16 cars to choose from, but to be honest almost all of them look and drive the same; the only one that "felt" different was the Yokohama. Finally, a paint shop and tire editor (available at the XCar web site) round out the package.