There are following problems associated with free piston engines (generators). Do you know if there exist some ways to overcome it? 1)Free piston engine burns oil.What could be done to reuse oil similar to four-stroke engine? 2)Free piston engine produces very short explosions which are claimed very difficult to muffle. How noisy it really is?As I know ``muffler`` works good even with pistol though pistol produces even shorter explosions. 3)Two stroke free piston engines are claimed to be less efficient than four stroke engines because they are two stroke.Due to short cycle fuel burns incompletely etc. Is it really so?And how much do they loose in efficiency?