Exactly. Known as Brake Specific Fuel Consumption (BSFC) derives that it takes X amount of fuel to support X amount of HP regardless of the engine type. Volumetric Efficiency (VE) comes to play when dealing with NA versus Force Induction applications but differences are legible for this conversation.

So end the end doesn't matter if it's a I4 or large V8, either will use the same amount of fuel supporting the same amount of HP.

Now comparing part throttle conditions IE (Fuel Mileage) is a different ball of wax. If we're really all that interested in one sedan gets one or two mpg better than other, the conversation from a monetary standpoint isn't worth a hill of beans when you break it out into annualized fuel cost. We're talking $150 bucks a year to drive one $30k vehicle over another $30k vehicle.

I mean....really....