On/Off switch for two cylinders in van engine?
 

How would I convert the engine in my Father's 3.0 Litre 6 Cylinder Caravan to run on four cylinders instead of six? I had this idea as my Grandfather had a truck which could go from eight to six cylinders though I don't know much else about it.

You've been here a while; search cylinder deactivation.

Basically, it isn't going to happen.

Maybe a 2.5L 4-pot to replace the current 3.0L V6 could be a good option, since it would benefit from lesser internal friction (thus improving efficiency) than deactivating 2 cylinders which would still generate some drag for the other 4 cylinders to overcome.

I could do that (Replace the engine with a 2.4 Litre model) but might wait, And end up with a 2002 2.4 Litre model instead; Those get higher FE than the 2000 models according to Automobile-Catalog.com:

2000 2.4 Litre (Average Range of 407 Miles estimate, 12 miles higher than the 3 Litre estimate - And I've seen 28.56 MPG or so on a 359ish mile tank)

2000 Dodge Caravan 2.4L fuel economy review (model for North America U.S.)

2002 2.4 Litre (Average range of 440 Miles estimate)

http://www.automobile-catalog.com/ec...n_ec_2_4l.html

I'm already capable of managing 24 MPG in the 2000 3-Litre; 26 is easy in a 2002 2.4 Litre with the ways and places I drive with what mods I have (Mostly without city/town miles lately.) Plus some mods and? I'm already sitting on 30.

That would be better. BTW have you never considered a Diesel engine swap for the van? I have once seen a Caravan with Argentinian plates and the Euro-spec 2.5L VM Motori turbodiesel...

Wow, No I had not but now I'm thinking of it! That would up the MPGs considerably high, Particularly keeping Diesel Dave's White Whale in mind. I'd actually like to do that.

Oh and BTW, The fifth generation caravans all get lower MPGs than the 2002 model (I didn't even see a 2.4 litre fifth-generation model, is there one?) despite being more aerodynamic, According to Automobile-Catalog.

Some year models came with a manual, that would let you shut off all six cylinders. ;)

But it might be harder to find one in America than in Europe.

If I'm not mistaken, the 5 spd caravan was only available with the 4cyl and only in early models, around '93-'95 maybe?

Not sure if exclusive to European versions assembled at Magna Steyr, but after that there were still some with manual transmission.