Sharpend
"Moreover, I love flying, so why fly at 150 kts when 120 kts is more economical and it takes longer to get to your destination (that is a good thing!!) ?
I have flown at 800 kts low level and believe me, 120 kts is more fun! For me anyway."
The reason I like flying at 150 kts in my RV-6A is because it allows me to still make 120 knots over the ground in a thirty knot headwind!
As others have said the throttle works in both directions and if I want to poodle around at 120 kts I can return a fuel burn comparable to any Rotax engined aircraft.
Also to enlarge on my previous comment to "Rod1", Lycoming have recently published a list of engines that can be run on MOGAS and many of these are fitted to various Vans aircraft.