I disagree. An engine is lightly loaded cruising at motorway speeds. It is acceleration, shifting a lump of metal and its contents up to speed that uses fuel. My MT 1.3 engine ran at about 2,500 revs at 60 mph and 3,000 revs at 70 mph. My 1.5 CVT engine runs at about 2,000 revs at 60 mph and 2,500 revs at 70 mph although this varies with gradient.. Cars use less fuel on motorways because there is no acceleration from a standstill and the engine is lightly loaded.