Best minivan for MPG
Dodge Caravan
It was the first minivan introduced in 1984 it was rated for 26 mpg hwy with a 2.2 L and 5 speed manual. Later the 2.5 L engine with a 87.5 mm bore and a long 104mm stroke was available until 1995. The newer 2.4L is an over under design. The 2.5 and 2.4 can be bolted up to a Neon 5 speed transmission with a 3.55 final and a .72 fifth gear. This would give 2000 RPM at 65 mph with 205/75R15 tires.
http://www.allpar.com/model/m/specs-2005.html
Toyota Previa
Longitudinal and rear wheel drive, the engine sits on its side under the driver's seat. The 2.4L 4 cylinder is an over square engine with 95 mm bore and 86 mm stroke. The 5 speed has a .8 fifth and a 3.91 final which gives 2500 RPM at 65 mph. Rating is only 16/20 - 18 combined mpg. If one with a broken rear end is found, it can be change to a chevy 3.07:1 then it would run at 1980 rpm at 65 mph.
Honda Odyssey
The 2.2 L engine was available from 1995 to 1997. The 2.3L vtech was only available in the last half of 1998, so it's rare. After 1998 only the v6 was available. It was common for the 3rd gear clutch to burn out in the v6 models. An Accord 5 speed can be bolted up to the 4 cylinders with a .685 fifth gear and 4.065 final this would give 2300 RPM at 65 mph. Prices for used Hondas are higher than domestic brands..
Chevy Astro
Bigger and heavier than the other minivans,and rear wheel drive its rated for 15 city, 20 highway. The 90 degree 4L V6 is a chevy small block v8 with 2 cylinders lopped off. A popular mod it to install a camaro 5 speed transmission. With a 2.95 rear end, the engine would turn 1800 RPM at 65 mph.
Chevy Ventura
Rated for 24 hwy/17 city, 20 mpg overall, the minivan only comes with a cast iron 3.4 L OHV V6 with an over square design, 92 mm bore and 84 mm stroke. The 4 speed automatic transmission has a .705 overdrive. 12 final drive ratios are available. A 2.84 final gear and it's 37/33 sprockets can be interchanged for 25% higher gearing. This would give a overall ratio of 1.59! The engine would run at 1280 RPM at 65 MPH with 205/75R15 tires! The cam shaft can be changed to an Olds to lower the HP peak from 5200 to 4700 RPM, peak torque would then be around 1900 rpm and best bsfc around 1800 RPM.
Quest:
Quest is simular to ford windstar with an oversquare v6 and automatic.
First generation Oldsmobile Silhouette 1990 through 1996:
It has a plastic body with and galvanized frame with futureized " dustbuster" styling. CD was .30. They dont show any rust, even after 23 years in the salt belt. The engine is a pushrod 60 degree 3.1 L v6 with cast iron block and heads, throttle body injection. 120 HP at 4200 RPM and 175 ft lbs at 2200 rpm, 8.8: 1 compression ratio. Transmission is a 3 speed automatic. Optional was the Buick 3.8 L 90 degree v6 with a 4 speed automatic with locking converter. A 4 speed non electronic 4T60 can be swaped in with the 3.1. The Ponticac Trans Sport has the 3.8 as standard after 1992. Both the Trans Sport and Lumina APV had a restyled 3 inch shorter nose after 1993, Silhouette kept it through 1996. The 1996 models all had a 3.4L 60 degree v6. Rating is 18 city, 22 hwy and 17 city, 23 hwy.