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.
For that size vehicle, your doing pretty well on mileage. When you say you did not see any effect by a grill block, I am pretty surprised. Further down you talk about a lower grill block. When I think grill block, I am thinking both upper and lower.
As far as a alternative vehicle, how many people are you typically having to transport. I agree with your assesement, from the standpoint of making payments, but I'm wondering if you still couldn't get something which would assist your transportation needs, at a lower expense. However, 18 with a full size truck is pretty respectable, in any case and maybe it will be the most cost effective.
Thanks for the encouragement. I dont have room for another car. Already a VAN in the garage for the family. My truck, moms car, and large boat in the drive. I thought about it, but decided to stick with a single vehicle. Thanks for thinkin about it though.
As far as the grille block goes, you can see in the pictures that just the upper grille is blocked for now. I have not yet figured out a way to block the lower grille. Upon inspection of it, the seam between the bumper and body is quite large and captures lots of air...so I need to block that too. Im going to tape it up with some heavy plastic sheeting for a test run. If it makes a difference, I will most likely buy a roll of auto-sign magnet 18" x 10'. My bumper is metal, and the magnet will stick to it, covering the lower grille and seam. I may just have to tape the magnets top edge to the plastic portion above the seam (since it obviously wont magneticlly stick to plastic). At least foil tape looks like chrome? lol....
The grille block was made by removing the honeycomb portion of the grille, the solid black piece remains in place. I taped the front of the honeycomb, and the filled in the backside with silicon caulk. Filled it enough that the back is a solid piece for each honeycomb portion. Looks good, adn if it heats up here in NC, I can quickly remove it without destroying anything. I am also still ascetically minded.
The tonneau cover was mad out of 2 sheets of tongue / groove insulation board, aluminum channels along the edges, angle irons for cross supports - all foil taped together. I then took it to the rhino liner shop and had them spray it on both sides, so it is waterproof and durable. It is held in place on the bed with aluminum angle riveted to the bed rails. bungee cords hold in down from the inside. total cost $300. Better than half the cost of the most inexpensive new hard cover I could find.
I also plan to use a fencing tension bar to allow for clearance around the lower rear body and rear tire. Then just slap a very large auto-sign magnet to the bod and that bar. This will create an easily removed wheel skirt, for accessing the rear tire when needed. The stuff isnt too expensive and seems to me a good solution to functionality, easy removal.
Looking forward to more ideas from reading all the posts. Have fun out there!
Look in to swithching over your engine, transmission and rearend to Amsoil. Amsoil increased my fuel mileage by 2 MPG when I switched to their 10W-30 Synthetic Motor oil in my 2001 Chevy Impala with 201,000 miles on the odometer!