Quote:
Originally Posted by Ringo64
The way I'm seeing it is that I can stay in the lower revs with a 6 cyl or 8 cyl which in theory I'm not over exerting the engine thus using more gas. The 4 cyl to get any power you're in the higher revs and over exerting the engine and using more gasoline.
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That's really not the way it works. Staying in the low rpms and not "lugging" the engine is how you get the best mileage, no doubt, but you are forgetting the smaller displacement, lesser amount of oxygen and fuel that go into those smaller cylinders, and so on. They will have that same range, but at a different RPM, more like 1800 for my boxxer vs 1000-1200 for my V8, but since the cylinders are much smaller, there's far less fuel and air going in than if the bigger engine was at the same RPM. There seems to also be some sort of misconception that the engine is being "overexerted", they have pretty good protections against that these days. All of what you said changes anyway if you turbo the 4, then it makes a lot more torque down lower at 2500-3000rpm and can accelerate like it got kicked in the rear at those RPMs (then drop off at the high ones).
Where you're killed in mileage is that the bigger engine has more power and can accelerate just a bit faster, which takes quite a bit more power. It's not a linear relationship where if you go twice as much power you accelerate twice as fast, nowhere near that. And of course you're turning bigger cylinders all the time and causing more drag on the system (lubrication for more and bigger cylinders, fuel pump supplying fuel to bigger and more cylinders, air being compressed, water pump circulating more coolant through engine, etc), not to mention the fuel going in there that powers all those parasitic losses. And then there's everything that comes with the bigger engine/more power, bigger drivetrain components, bigger brakes, the heavier engine, and so on.