3.0 liter 4-cylinder = 40mpg?

[JapDane2]

Here's an idea. Make a 3 liter 4 cylinder that's very undersquare and makes peak tq at about 3500 rshared_pm. Then gear the trans so you are reving about 1500 rshared_pm at 65 - 70 mph. You wouldn't have to beat the hell out of it on on ramps and you wouldn't have to down shift going up hills. I think a 3000 pound car would get 40ish mpg with an engine like this.
Any thoughts?

[Loren]

If that were so, surely the Chevy Colorado pickup with a 2.9 liter 4-cylinder would get more than 25 mpg.

[treekiller]

Displacement is displacement, regardless of number of cylinders. for every 14.7 parts of air 1 part of fuel must be added. this is starting to change with direct injection as they can direct "rich" zones in front of the injector nozzles so they can use less fuel under low demand situations.

The Qr25De engine in the sentra SE-R is an example of what you're saying. I owned one for years and it was fine being lugged along at 1500RPM's on the highway.. 40MPG.. close if I kept my foot out of it. and Loren... 25 for a pickup is awesome, considering they aren't exactly light or aerodynamic. I've said for years that engine should go into a nice RWD car.

[SixCylinders]

I'd believe it, I've gotten 35mpg on the interstate using a 3 liter V6 and a bad O2 sensor.