Is this just because it's a hatch vs a coupe style hatch like the RSX? I can't imagine it's because the Civic has more "accessories" or a stiffer chassis than the RSX. What's the deal?

Civic Si = 26/31mpg
RSX = 27/33 mpg
RSX-S = 24/31 mpg

Civic Si = 2782 lbs
RSX = 2694 lbs
RSX-S = 2767 lbs

 

Aerodynamics would be my guess, I'm sure being a hatch there is more turbulence in the rear draft of air behind the Si than the lower rear hatch on the RSX...not a big difference either. Might be error.

 

The USDM EP3 has the Type R axle ratio.

 

i see difference in the 100lbs or so in extra weight the si has over the rsx

 

the k20 in the rsx is more power, how can it consume les gas? it just doesnt make any sense

 

Tap tap tap.... Ummm.... Hello?

 

it doesnt matter.... the type-r axle ratio is shorter, if anything it should consume MORE gas

 

opps, the ep3 is the civic, i thout it was the rsx, sry, yea that would explain it... why don't they just put the k20 from the rsx into it then with the RSX final drive. if it is faster and more fuel effcient that way, i dont understand why not

 

Fuel mileage is a strange animal. Like mentioned above, gear ratios will make a big difference as does weight and expecially aerodynamics.

However, as for the engine, fuel economy comes from the enignes ability to run lean and still makes good torque/power at throttle positions under 20%. High compression ratios help quite a bit.

Ultimately, teh city numbers are almost the same. THe big difference is in the highway numbers. I suspect that although the RSX does not have a significantly better coeffecient of drag, it does have a slightly smaller frontal area. It's a smaller car than the Civic.

 

We typically average 25-32 mpg in the RSX-s. I don't just cruise around in VTEC because it sounds cool either. Neither my wife or I are slouches on the gas pedal either and the redline is not a stranger. I typically average about 85-90 on the exways, but stay close to the limit in towns.