huh. I wonder if lowering your rpm will make the motor use less gas?

 

Going to a bigger tire or lower gear will indeed lower your RPM and allow you to use less gas, but then you have to think about the situations when low-end torque is needed. As you know, bigger wheels and tires will undoubtedly add weight, so lowering the gear ratio is the best way for you to get what you want.

On my Viper, I went with a larger diameter tire/wheel combination, but I paid $6K for a set of 19" Aluminum Billet Wheels which are 5 lbs lighter than the factory 18's. The lighter unsprung weight was enough for me to tell a difference when taking off from a stop. Since the RPMs were lower in all six gears, I changed the rear end from the factory 3:07 to a cryogenic 3:55 to give the car an even bigger kick in the pants boost from the line. The larger diameter tire changed the effective ratio to 3:33, which still allows a high end speed above 170 MPH.



Of course, I am not too concerned about gas mileage when driving my car.

KR-Texas (BlackVenom)

 

So KR,

Have you read the lit on Gear Vendors Overdrive/Underdrive? I seems your contribution to this thread proves that most of the mods you did, have little effect on mileage compared to dollars spent.

 

I know this is off topic a bit but..

Superslab, what wheels have you been looking at.. I have the same 7 lug crap (WHY DIDNT THEY JUST USE 8?) slim pickins out there.. centerline wheels said they could make some for $295 a rim..

 

I'd say take your 5k and but a DD that gets 20-30 mpg

 

Centerline is not that creative with their rims. Alba has a few models that are actually good looking. They also have good chrome, which make cleaning brake dust off easier.

 

I have not read the lit on overdrive/underdrive. I agree that my mods will not pay for themselves with better gas mileage. The truck runs better and sounds better, but the extra 2 MPG when driving on the highway will take a lot of miles before I will be seeing any real savings.

I wanted to post the information on what I had tried because a lot of folks read about different gas saving tips and think the effect is additive. I think you can only do so much with these trucks before the overall weight becomes too much to overcome. I did not lower my gear size because I have a boat and I did not want the truck to struggle when towing. The overdrive/underdrive idea might have been interesting, had I known about it.

Now, I am looking at a new FX4 with a 3:73 gear, so I am going to wait to see how it tows my boat.



KR-Texas

 

hahahh i live in Hampshire IL, and I'm pay in 2.95 for 87, you are lucky

 

You can gain at least 3 MPG using the following techinique:

1. Reduce overall vehicle height. Lower the front by at least 2" and rear by 4"
2. Lower your rear end gear ratio to 3:55 or less.
3. Fold your rear view mirrors in.
4. Wax your vehicle (including chrome and tires) once a month.
5. Overinflate your tires by at least 3 psi. Also switch to summer/high performance treads during warm temps.
6. Reduce your overall wheel weight. Larger rims that weigh less and handle lighter tires are ideal. Remember, the tire is the heaviest item, not the rims.
7. Drive slower than 70 MPH.
8. Place the trannie in neutral during deceleration.
9. Use power adders, like superchargers and turbochargers. These will increase engine efficiency, even when the engine uses power to run them.

I did this and yield 22-23 MPG on the highway if I stay between 66 and 70 MPH.

 

Talk about obsessive...great that it works.

 

I used to tow a boat (4000lb SeaRay) with my old F150 3.73, with no issue. I'm actually interested in the Over/Under because:

1. I'm building a house in the next two years.
2. After that I'm having a twin diesel center console boat built, which I will haul with my truck.

Thats-where I dont think a 3.73 will go. Now that I have a 4.10, I like it except for the mileage.

 

Correction: Prices are 2.70 per gallon on Halloween.

 

RoushF150,

That is very good indeed. I have seen mine go as high as 19 MPH for long stretches on the highway. I have tried most of the items on our list, except for the power adders and the folding mirror trick. I think the OP does not want to spend that much money, plus his truck is a lot taller, so he may never be able to acheive the same mileage.

KR-Texas

 

If you reference the earliest posts, I presented a list of mods, in order of importance, and the forum members responded with their experience regarding one mod or another.

It has been my goal to add mods that effect economy THE MOST, because it has the biggest payoff, sooner.

All mods are on the table for me, as I intend to keep my truck well past most, to use as a tow vehicle.

Ironically, FORD chose to limit value-added options, because the average truck buyer can't afford them. That logic seems moot if you look at this core group of owners on F150online.

 

The target here is a gain of 2 mpg.
If I gain an extra 54 miles per tank, based upon the cost of $0.26 per mile, that translates to $14.04 savings.

For me to travel 405 miles before mods: $105.28.
For me to travel 405 miles after mods: $93.15.
Real savings per 405 miles: $12.13

Average travel of 12,000 per year:
@ $0.26 per mile | no mods = $3120
@ $0.23 per mile | mods = $2760

Yearly Savings: $360
3 Year Savings: $1080


Over time, with gas prices steadily increasing, those savings amounts actually grow. There is a lot of debate as to whether it is cost effective even to get mods. Without premium synthetic fluids & tuning, those mods never reach their full potential. However, if you tune, it would only make sense to get the most out of your truck, and that is with a high octane tune. Higher octane gas could be as much as $0.35 higher per gallon. The true benefit to the mods, and tuning, and using premium synthetic fluids; you are driving a nicer truck. Do it all and your truck runs better and will possibly last longer.