Like I mentioned in one of the recent threads, you could open up your flash implementation and call it Unigine Flash Player. Flash is in need of a good alternative interpreter, and if one were to appear, it would produce quite a stir, in my opinion; this would raise the Unigine brand awareness. If the flash player turns out to be better than the original (not a very tall order, honestly), it might even start to replace it on many PCs. Since flash is installed on like 95% of computers, that's a lot of eyeballs being exposed to the Unigine brand. People might start wondering what is this Unigine is, google it, and voila! find out about OilRush.
Yeah... Or, once the initial interest in OilRush fades, you could contact Humble Indie Bundle and become part of their next pay what you want giveaway. These have proven to be quite profitable and, at the same time, popular. Who doesn't like the idea халява?
As I understand, OilRush is not just a game for Unigine; it's a game that advertises the Unigine engine at the same time. The more popular the game is, the more likely customers are to buy licenses for the engine, so popularity gimmicks are something Unigine should focus on (IMHO).