v10 torque vrs diesel

Ok guys. We had a 2011 38ft. Georgetown with the 362 hp Ford V10 and town a Chevy Equinox. The Ford performed admirably and I never had a problem going up steep grades, but if I tried to maintain 60 mph on these grades when the tranny downshifted to second gear, which it almost always did, the rpms would go up to about 5000 and the engine sounded as if it was going to explode. The highest mpg I ever got with the V10 was 8.2 and most the time if I maintained 60 mph I'd get 6.8 to 7. So, don't even try and tell me about 9-9.5 mpg with a 38ft. motorhome towing a car. We now have a diesel pusher with a 330 hp Mercedes engine. I constantly get above 8 mpg and have gotten as high as 10 with a tailwind, and this is on a 42ft. motorhome towing the same chevy equinox. I have never found it to be lacking power. When I set the cruise control, usually at 62 mph, it seldom downshifts out of 6th gear and of course there is absolutely no engine noise up front with the pusher. While I never went over mountains with either, being a fulltimer, I have been over the exact same routes with both units, and in my opinion the diesel pusher is the way to go. I will say though, the Ford V10 handled my Georgetown very well, it was just to noisy for me. Oh, and as far as my mileage comparisons I used a scan gauge on both units.