[Pontiac]

Don’t you need a little friction to get some compression?

No

If it were possible you could get compression with zero friction.

All that is necessary for compression of gases is to reduce the volume of the container.

In an engine this is a mechanical process and so friction is unavoidable.

[smokingfrog]

get a patent for your frictionless piston rings

you’ll make millions!

[TexasGator]

“In an engine this is a mechanical process and so friction is unavoidable. “

But reducing the friction leads to efficiency gains.