I would try it on my full size v8 truck. My last two tanks have been 17mpg, pretty decent all things considered.
I actually got the idea because I was thinking of installing a homemade intake that I've seen on similar models. It costs nearly nothing and works great, one person who did it for more power reported FE gain. However, it was done on a model a few years newer than mine and mine doesn't have space. The difference is the fan...if I install the e-fan I'll have the space I need for the intake.
If the combination of both will pay off pretty quickly, I might do it. I don't put a lot of miles on the truck, I currently do most of my driving in the little VW. Money is tight for a mod that won't pay for itself quickly...
It depends on the condition of your existing fan clutch.
If the existing fan clutch is in good condition I imagine you would see noticeable increases, if the fan clutch you have now is worn, not so much.
The increases come mostly from the greatly reduced air flow. A typical mechanical fan in good condition will move 12,000-15,000 cfm peak while an electric fan will typically move around 5000-8000 at the most. With electric fans the same 5000-8000 cfm of air flow comes at a greater loss but you can turn it off and rid of all losses instead of a clutch just getting loose. A company used to make an electromagnetic mechanical fan clutch but I can't find them at the moment.
Something to look at might be the new Silverado. It comes with electric fans.
I just converted from mechanical to electical on my 67 Mustang. 14" fan was 66$ and adjustable thermostatic regulator was about 56$ (rip off!). May put a second one on the reverse side, but I need to take some measurments..
You can pick up a few ponies too by reducing your mechanical drag..
It frees up a little power but time and time again people are seeing the faster a car gets to operating temps the better mpg's and the emissions go way down. Electric fans help. You are going to be greener for both reasons. A 3.8 ford taurus fan moves a lot of air and is cheap at the local yards. Its the same one used on mustang and other late 90s v8 fords so im sure its fine for your application. A bonus is even tho a vehicle came with a mechanical fan the ecu might have a lead for the fan, so you can swipe a switch from the same brand of engine and make it very oem reliable. I would wire in a toggle as additional peace of mind.
Where are you guys getting those electric fan setups? I am considering one for a restoration project I have in the works. JC Whitney has them but they seem expensive. So you need the fan, the relay, and a temp. switch (Thermostat)?
BTW: My resto project is a 1963 IHC Metro Mite, which is a small step van. It is super cool but light years from being road ready. It has a 2.5L 4 cyl and a 3spd manual. Not sure what I'll get for mileage. It's as areodynamic as a couch but not super heavy. The old advertisements brag about great fuel economy but that was 1963, when most (american) cars were, what, 8mpg??
When it's finally ready for the road it won't see much use. Just the occasional hauling of band equipment to local places or drives to nearby truck shows.
Check it out on flickr. http://www.flickr.com/photos/47792194@N00/260971412/
Also, there is a link to my project page on flickr, but that site hasnt been updated. I've since replaced the clutch hydraulics and rebuilt the carb. Now it runs and moves on its own power, but has no brakes at all so you gotta be careful!
step one, go to a junkyard and pick up an electric fan out of a car that has the same engine as yours (4 banger-4 banger v6-v6 v8-v8) It doesn't have to be liter specific or even same brand, just get a fan and the plug that plugs into it (cut the wires about a foot long, longer the better)
step 2; go to any auto parts store and ask for a universal electric fan kit, should have an adjustable t stat with a probe coming off it. i got that and a few other stuff for it for like $17...
then you just need a simple 30A 12V relay (if your lucky you can find after market ones on stock cars (typically power fog lamps, alarm systems, etc)
don't need new fancy flex-a-crap fans or $60 fan controllers...