same materials make a poor bearing surface, but that is usually in the context of galling/wear, can't see it being a big factor in creating drag. use a very light oil, like instrument oil; haven't used 3in1 in ages but iirc its heavy. after that is matter of design, construction (everything square, no binding etc) and how tight or loose it is (clearance between mating parts). These little wobbler engines are not very efficient though, ie no matter how precisely you build it, there's a lot of friction between the cylinder and stand, held together by the spring, still you'd' think 10-15 psi would be more than enough. How freely does the engine turn over?