I had posted Steps one and two of this letter as a reply to a gentlemen who was contemplating buying a fan setup for mileage purposes. I have since completed work on the truck and have been fortunate to cheaply increase the mileage from 14.2 to a fairly decent number (for pickups, at least). Hopefully, this will help someone else.


After buying it in late January of 2005, I soon discovered my 97 F-150 XL 4.6L SuperCab Short bed was getting 14.2 mpg. This was from a combination of very little city driving and going 70-80 on the highways. It got down to 8.something when towing our Boy Scout trailer - EGADS!!!!

Life is too short to drive 55, so there had to be a way to get some better mileage. Being an Engineer who likes to tinker, I got to thinking . . . . . .

Step one: Took off air filter & MAF plumbing and installed a cheapo $26 air intake/MAF tube from E-bay. Also changed the plugs after 162k miles. Power is up slightly accord to my 'seat-dyno', and mileage jumped to 15.4 - plus there is a lot more room under the hood.

Step two: I took off the fan & clutch and ran it a week with no fan at all. She jumped up to 16.9 w/no cooling problems. However, the AC did not work very well, so I added a salvage yard electric fan. Cost here was $65 including sensors, relay, etc. A huge plus is that there is now even more room under the hood.

Step three: BBK Underdrive pulley kit ($55 used, cheap on e-Bay). The AC still works well, which is pretty important in West Texas, and the truck does not overheat. Mileage is up to 17.5 or so. I thought it would improve even more than this, but was mistaken.

Step four: These trucks are almost as tall as they are wide, which means you a driving a sailboat down the road against the wind. From Engineering, we know that drag is a cubic function. That means if we double our speed from say 45 to 90, it takes 8 times as much horsepower to overcome wind resistance at 90 as it does at 45. That is why hot Mustangs and Camaro's get better mileage than stock pickups at speed above 70. Anyway, I lowered the rear end 4 inches with a kit i bought for $35 on eBay. I later figured out I could have done it for FREE if I had drilled new holes higher up where the rear spring hangers mount. Then I cut 1.5 coils off of the front springs with a torch - to do this properly, take the springs out, cut them, let em cool completely and then re-install. This lowered the whole truck roughly 3 inches and seriously lowered the drag coefficient. Mileage up to 18.4 . . .

Step five: Old tires were worn and getting hard, plus they were two sizes too large and very wide.
-I weighed one and the rim/tire combo were 77.5#. Way too much sprung weight to get any mileage around town.
-They were over 10" wide - rolling resistance and subsequent friction from wide tires will kill mileage.
So I opted for some lighter rims (yep, eBay, $160 with shipping) and four new tires (General Ameritrac SUV in 235-75R16). New tires are 9.25" wide and tire/rim weighs 54#.

Mileage is now up to 19.6 as long as I keep my foot out of it. Total investment was about $350 plus the tires, which I needed anyway. Good luck on yours, and if anyone has other ideas, please let me know.

Thanks, Logger

 

In my mind...thats just $350 I could have used for gas

But seriously...great thinking! You could probably add an exhaust system and improve even more.

 

At 19.6 MPG and driving 12,000 miles per year you use 612 gallons of gas at $3/gallon that is $1836.
At 16.9 MPG (half savings for mods and half for attitude) driving 12K per year using 710 gallons for $2130 is a difference of $294 per year.
This means you will pay for your mods in ~1.2 years depending on variations in gas pricing or the number of miles driven. You probably drive more miles per year in West Egypt Texas since everything is two+ hours away.

Of course you probably should not include the cost of the plugs. You may notice overheating problems in traffic this summer and lower mileage when your alternator has to power that fan. If it overheats you can always turn off the AC, crank down the windows, and crank up the defroster. It may get a little uncomfortable and the defrost fan will draw more power cutting mileage but you will be saving gas. When you hit the highway you can crank the AC again.

A vacuum gage is always a good reminder to keep your foot out of it... Bet you could even rig up a little red economy warning light!

 

Good ideas man! Im actually kind of amazed they made that huge of a difference, wow!

 

Overheating was a concern, but has not been a problem so far. The pulley swap was done prior last summer, and so far 'no heato'. Curiously, I had swapped pulleys on my wife's Tuned Port Firebird and it made about 15 more foot pounds of torque. So when I swapped the pulleys on the F-150, I was expecting either much better mileage or power. Although it helped some, it was not as much as I was expecting.

By the way, as a lifelong Chevy guy who had some terrible experiences with Ford corporate cars & trucks in the 70's & 80's, I am impressed by how smoothe & reliable this new generation of Ford engines are.

 

I didnt realize ford used coils on these trucks, thought they were all torsion bars. Torsions bars would probably be easier to adjust though than cutting. I have been saying quite a long time the main issues with poor milleage and you have hit the mains ones right in the head. The problem is some of us want our 4x4 trucks tall and with the biggest tires that will fit, so we are forced with the poorer milleage. My v6 is getting mid 14's. I havent tried messing with the fan or pullies yet though... keep up the good work.