I would not recommend someone blasting a car with aluminum oxide. It can be done, with very good results, considering the person knows what they are doing and uses the correct size (grit size) of material. But, as the others have said, there are other products that are alot better to use and will not run the risk of warping any panels.

Aluminum oxide comes in a wide array of sizes. (as large as 10 grit, and as small as 320 grit) Starblast is a 120 grit material. Assuming blast pressures are equal, 120 grit aluminum oxide will do the same job as Starblast and leave the same finish. However, aluminum oxide is a much more aggresive media that will work alot faster. Starblast also has the natural ability of not creating as much friction heat as most other hard abrasives, this is why it is used on thin metal without the high risk of warpage.

You hear people talk about removing metal when blasting with different types of abrasives. The amount of metal that is removed (even when using aluminum oxide) is very minimal. About the same as when you sand a metal panel. It takes someone who really doesn't know what they are doing (or someone who is intentionally trying) to remove an appreciable amount of metal by blasting.

David