Compressed air has great power density, but awful energy density. I.e., you can unload power very quickly from it but can't store much at all.

Looking at this http://www.popularmechanics.com/automotive/new_cars/4217016.... popular mechanics article, this engine uses 340 Liters of air (under STP) compressed at 4350 PSI.

If my math is right, that only provides a theoretical maximum of about 55 MJ of energy, which is about the same as about 1.5 liters of gasoline.

A combustion engine runs at about 20% efficiency and, if memory serves, compressed air engines at around 30%. But let's give MDI the benefit of the doubt and assume their engines are 50% efficient.

That means this car claims to be able to go 200-300KM (125-185 miles) on the equivalent of about 4 Liters (or 1 gallon) of gasoline.

Now, getting 150 miles/gallon isn't physically impossible, but it seems pretty difficuly and does raise some red flags to me. And that's assuming they have a 50% efficient engine, which is extraordinarily unlikely. Assuming a 30% efficient engine, this car is doing the equivalent of 250 miles/gallon.