You will gain power and fuel economy - and of course the possible higher level of detergents. In my experience the mpg gain does not quite amount to the price difference, but as said there are power and detergent benefits.
This is not true. Higher compression engines yes but itd be specified in the user manual. If it states 87, its 99% likely to be a waste. Ive never noticed any difference on any of my vehicles. Same mpg and power.
I dont know if i buy intothe detergent benefits..regular having the minimum standards, ive never had any fuel system issues, as most others, so hard to prove those detergents change anything.