The QUESTION was if driving slower saved the machine, or just gas.
Without regard to what I feel about your speed being sufficient or not and the ramifications thereof, there is no benefit to the machine, so the only benefit is to the gas. And, the savings here is minimal.
When the speed limit was lowered to 55, it was hoped that the fuel consumption would be about 2.2% less than the then-current consumption. Studies by the Department of Transportation found the fuel savings to be closer to 1%, and an independent study found the reduction to be only about
0.5%. Contributing factors to the new consumption rates staying as high after the new speed limits as before the limits was that the 55 limit was widely ignored. (I have to assume that a return to a mandated lower speed limit would also be also be widely ignored. One can save fuel on a personal level, maybe, but on a national scale it has been found that lowering speed limits does not work to save fuel.)It turns out there is ample discussion on whether the lower speed limit was safer, and some studies show that the lower speed limits actually raised accident rates. (Without reading the studies, my guess is that the vast majority of the population that ignored the rule ran over the minority that observed it...)
None of your feelings on your comfort, or mine, have anything to do with the topic that was raised. And to answer the question presented, while there is no mechanical advantage (in terms of saving wear and tear) there appears to be little advantage to the fuel consumption either.