Gas mileage?

Can anyone especulate why the difference in gas mileage among these three vehicles?

Isuzu rodeo 91-97 3.2 ENGINE SIZE

Curb Weight, lbs. 3545

V6 3.2

5-speed manual: 16/19

4-speed automatic: 15/18

Isuzu trooper 1990 2.6 ENGINGE SIZE

Curb Weight: 3755 lbs

Manual: 16 mpg / 18 mpg

Automatic: : 15 mpg / 18 mpg

Honda CR-V 2002 2.4 / 162 ENGINE SIZE

Curb Weight, lbs. 3318

5-speed manual: 21/25

4-speed automatic: 22/26

THANKS,Gas mileage?
In almost all cases, manual transmissions get better gas mileage.



But between the 3 vehicles you have listed there, I'd say it comes down to engine size and curb weight. Notice that the 02 CR-V has a 2.4L engine and is the lightest, and it gets better mileage. The smaller an engine is, the better the gas mileage.Gas mileage?
Why?