Inline 4s

Hey guys,
I just have been wondering how you all were doing with the inline 4 engines. My strongest one is about 230 horsepower, so I could do better much with a V. Also a quick question, how do I know the miles per gallon (mpg) or do I need to make a model of a car for that which the demo doesn't seem to want to let me do. Thanks
I just have been wondering how you all were doing with the inline 4 engines. My strongest one is about 230 horsepower, so I could do better much with a V. Also a quick question, how do I know the miles per gallon (mpg) or do I need to make a model of a car for that which the demo doesn't seem to want to let me do. Thanks