technically the bigger the engine the more fuel used to run. the golf would use less fuel, but then it depends on driving conditions, if the person driving golf accelerated as fast as possible and kept driving like that, then one can assume his fuel usage would be higher than just normal driving.

In general big engines use more gas than small engines.

But that is the general case. You will find that Corvette is very good on gas on the HWY. That’s because the car is so aerodynamic (and light).

So for specific, you would have to look up the detail.

But in general bigger = more gas.

Good Luck…

Depends, partially, on how fast you’re going; which engine is spending most time near it’s sweet spot (and how much the car weighs, engine age, etc,). All other things being equal, averaging 70mph my money would be on the Golf returning better mpg.