My friend gave me his used set of 31.5x10.5 R15's Good year Wrangler RT/S load range C tires.
He drives a toyota tacoma, since he gave me his old tires and replaced them with yokohama A/T's and also has a set of yohohama mud tires. He got 25mpg with the good years and has not been able to match...
Saab did make a variable compression ratio engine back in the early 1990's. As you can see it never went any where.
The GM LS2's with displacement on demand use solenoids on the hydraulic lifters' oil supply to collapse the lifter shuting the valves, this helps with pumping losses and of course...