Indeed, mpg gains have been astonishing. Much of that has to do with engine efficiency, and alot also to do with aerodynamics. Cool to see actual science/engieering make life demonstrably better. My old MGB used to get a predictable 21-22 mpg. Now my Dodge pickup with a 400 hp V8 does better than that. Amazing. Same with my new ride, the Vette. Like the truck, it’ll shift to a 4 cylinder mode when load conditions permit. In it, the computer claims I’m getting 30 (!!!) mpg out on the highway, and around 17 in town. And that’s with me romping on it with impunity. Very cool.
Actually, these gains are mainly due to more gears in the transmissions.
Yes, Variable Cylinder Management helps on the highway for sure, but the majority of fuel economy gains have been due to the fact transmissions have been given more gears.
Not all that long ago a typical car might have 4 gears, today most have 6 or 8, with more 8 quickly becoming the norm.
Hell, the first truck I ever was in, was a 70s ford as a kid, that had 3 on the tree. Only 3 gears. My 1969 250 I bough as a toy, had 4 on the floor counting the creeper gear... (So effectively a 3 speed as well, though that creaper gear was a lot of fun truck was jacked up, had 33” mudders on it and loved to take it offroading, but I digress)...
CVT’s also aid in this, (Fuel economy) though personally I would never buy a car with a CVT transmission, ever. They just don’t last... Honda as an entire brand has taken it on the chin across their lineup in terms of reliability in the last few years and its all because they went CVT transmissions across most of their lineup.
Yes there have been some engine improvements too, but the majority of fuel economy improvements in the last decade or two have been mainly due to increasing gears in transmissions over engine improvements.