Still have a long way to go....

[jeffreymccoy]

2004 F150 4.6L Auto

Some history. I have an 04 F150 that is paid for with low mileage (38K). I have a large family, and an acre lot. It is nice to have the truck for hauling things that I need. I do most jobs myself. I dont need this for everyday driving though, so I decided that I could give up the truck and either have materials delivered or rent a truck when the occasion presents itself. To that end I began my search for a new car that would get the best mileage possible. I looked at the civic hybrid, prius, yaris, and fit.

After making some assumptions on annual driving and gas cost for comparison purposes between my truck and a new vehicle, it was decided that I could only finance $5K for a new car and immediately start saving money. Any more than that and I'd be breaking even or spending MORE for 5 years (loan term) before saving any money on fuel. Basically, cost of truck fuel for one year had to be less than new car payment + new car fuel cost. Keep in mind that these numbers were based on EPA estimates for all vehicles. I had to make some assumptions for the math to be consistent between vehicles. The numbers just didnt work out, and I am keeping the truck. It doesnt make sense to me to spend more money for 5 years before I start saving. Most people dont even keep a car for more than 5 years - and I cant say that Im one of them. OK now what do I do, I say - and then I find this site and all the wonderful information you all have to share! Hoorah, Im on my way I think...

I've been reading a bit and decided to work on aero mods first, trying to keep cost down and return on investment high - which I calculate in miles to drive before cost of improvement is covered.

I have baselined 2 tanks and purchased a SGII for the 3rd baseline.
1st tank = 16 mpg
2nd tank = 17 mpg
3rd tank (SG) = 19 mpg

I built my own tonneau cover and grille block and began with the A-B-A testing today with those and the additional steps of removing passenger wiper and increasing the tire pressure from 35 to 50. All tests below measured with SG.
A = 18.3, 19.3, 20.5
B = 19, 19.1, 20
A = 20, 19.2, 20

I saw a negligible difference between grille block and no grille block, as expected. I also spent 1.5 hours on this A-B-A test - just to confirm little difference. I am an impatient person - so I decided to make all changes at once and see what happened. After all, I realize that aero mods work together and that individual changes dont make a big difference, but cumulatively - they can. I added the tonneau cover, grille block, 50 PSI, and removed the passenger wiper. Off to the course for the test...

A = 19, 19.2, 20
B = 20.4, 22, 20.6
No final A (didnt undo everything and retest, ran out of time today).

The first number in each case is a 10 mile stretch with stoplights, rolling hills and some traffic, tried to keep a speed of 60.
The second number in each case is a 12 mile stretch of highway, small low grade hills, kept speed at 70.
The third number in each case is the same 10 mile stretch as the first number, just opposite direction.

So on my highway run, it looks like the mods gave me an increase of ~2.8mpg, or roughly 15%. Im not sure which is right, the 16/17 mpg baseline, or the SG 18/19/20 baseline. To be sure, I will manually calculate this next tank of gas and use that number as a final increase value as compared to the 16/17 baseline values. This will be my best comparison, cause I just got the SGII and still need to calibrate it (pumped gallons vs what SG thought it received). Based on 16/17 baseline, and if I really get 22 on the next tank calculation, then I only need to drive 12,900 miles to recover my costs...LOL.

Next on my list is a full under body tray, lower grille/bumber seam block, rear wheel skirts, possibly a boat-tail from the rear of the cab to beyond the tailgate (truck may be perfect for this). I dont know what else I could do aero wise to get any improvements (I need my mirrors - sorry).

I dont get how some of you guys get such huge mileage gains.... Im hoping to just double my EPA and get 32 when its all done. I know that my driving style will have the most impact on that. Im hoping the SG can re-educate me!

Thanks for all the great info here, and for everyones contributions. Anyway - Ive rambled on enough now. Cheers.

-Jeff