2005 Subaru Outback XT MT / 2012 Subaru Outback 2.5i Premium
Next time I drive it 80 mph, I'll get you the numbers for a hill and a flat.Demonstrably not true. Hyperbole, maybe?
In top "gear" ratio, the H4 Outback runs 32.2-32.5 mph per 1000 rpm (depending on OE wheels/tires), while the H6 runs 37.0 mph per 1000 rpm ... about a 12% difference. (Source: 2015 Legacy/Outback FSM, OEM tire "revs per mile" data) Thus, cruising at 80 mph, an H4 Outback would be turning ~2470 rpm, while an H6 would be turning ~2160 rpm ... hardly "half the RPM."