Engine frictional losses are an area of study for engineers for a long time now...
Japanese production motorcycle engines are all good example...
Crazy-high revs, very thin rings, next-to-nothing piston skirts, etc...
I remember reading an article years ago on building a production "stock" race engine...
How they measured and remeasured crank plain bearings to the "upper" tolerance for lower friction, mixed and matched parts to static balanced reciprocating assemblies (rules don't allow for removing material)...
The HP gains, and thus economy, we're substantial....
Have a look at this Ducati piston..
http://www.fastdates.com/PLN.NewBike....58Pistons.jpg
Small skirts where fore and aft load from the angle of the connecting rod push the piston against the cylinder wall...absolutely nothing on the sides where no load exists, save for the ring land area.
200 HP/liter specific output for production 4 stroke engines are practically common place anymore.
Amazing....