Ah. Tony knew well enough what that particular choice meant - it meant there wasn't any choice, Clark was bored and the usual fare probably wouldn't satisfy it, so he had to come up with something better. Luckily, he had something in mind.

"Well, I have been working on... let's call it jet fuel," he rifled through his papers before pulling out one covered in equations and chemical symbols "A few easily-obtainable ingredients, the right car, the right stretch of highway... I could nearly hit the land speed record with this stuff." Well, that or melt the rubber off the tires and burn out the engine, but that was science for you.