[smokingfrog]

I see what you’re saying, but it’s pretty difficult to have motion without friction unless you have something moving through a vacuum. If you stretch and compress a spring rapidly, it’s going to get hot. The motion gets converted to heat. There’s a lot of heat in an internal combustion engine and all parts are not going to expand and contract at the same rate, so pretty difficult to reduce the friction of all the moving parts by a significant amount. Parts are lubed with oil to reduce friction and remove heat, but the oil itself even creates some friction. Am I missing something?

[Yo-Yo]

No, I think we are mostly in agreement. You first said you need friction to have compression, but your last post says that friction is hard to reduce to zero.

We agree there, friction is not necessary for compression, but friction will be an ever present parasite.