One of the factors that seems to allow small displacement engines to use low rpm at constant highway speeds, is the advent of many gear transmissions. The newer 6 to 8 speed transmissions and in the Jeep Cherokee's case....a 9 speed are quite a jump from the 4 speed automatics of not all that long ago.
I think both the increased number of gears , the ability to have a greater number of closer ratios and improved automatic selection of the gear ratios in modern, current transmissions has been a boon to keep smaller engines within their power band.
Also engines...of all displacements/forced induction/non forced induction have benefited from variable valve timing and/or forced induction systems particularly those where there are two turbos...one for low speed 'launch' and the other turbo for punch, higher in the power band.
Amazing what technology has and can do. But to me the caveat is...that's a lot of expensive equipment to gain wide powerbands and multi speed transmissions to take advantage of it.
What happens when it needs to be fixed ?
