wintersun wrote:
More cylinders means more pollution and more pumping losses and so poorer fuel economy for two similar displacement gas engines.
This is incorrect in my experience; of the three RVs I've owned in the past 25 years, my current rig is the biggest and heaviest with the largest engine and the most cylinders (V10 vs V8s.) The V10 gets by far the best mileage of my 3 despite being by far the heaviest and physically biggest rig, and being driven much harder (because it can handle it.)
There is much more to mileage and pollution than displacement or number of cylinders. I'm sure my lawn mower pollutes more than my 2019 V10 RV does.