I can only assume a lot of you are trying to improve you current gas milage, am I right? Well, I have 98,000 miles on my 05 5.4L and I have been testing several different product to increase my fuel economy. Here is what I have learned, take it for what it's worth, I am just hoping to shed some light on this struggle.

At 60,000 miles I was getting 15 miles per gallon, I have 3:55's and an Auto Trans. this is pretty close to the milage I had been getting from the start.

At that time I did several things to attempt to increase the fuel aconomy, I am an average driver (not heavy footed at all).
I changed my fuel filter, no difference expected, none gained).
I then changed over to a K&N air filter (50 bucks), this increased performance slightly and I only gained about .4 miles to a gallon over 5 or so tanks of fuel.
I then changed my oil with semi-synthtic and one quart of Mystery oil. (ran alot smoother but no increase to power or fuel economy).
I purchased a Hypertech max performance programmer. This made a noticable change in power and fuel economy (275 bucks, increased to 17 miles to a gallon)
At that time I was at 80,000 miles, I changed my plugs and boots (ran again smoother and increased fuel economy 225 bucks included the lisle tool)
lastly I started using Lucas brothers fuel treatment (probably did the most bang for the buck, increased fuel economy as long as it was being used 9 bucks for 100gal treatment)

So all in all I spent 560 bucks to go from 15 miles to the gallon highway to 18 miles to the gallon. So what does this equate to:

15 miles to the gallon I went through 30 tanks of fuel a year, @ 2.85 a gallon it was 2308 bucks

now at just short of 19 miles to the gallon, I only use 23 tanks of fuel a year, 1769 dollars a year.

I save 539 dollars a year.

Bottom line is if you are looking to put money back in your packet, don't expect it to get there over night, it will take about one year to get your money back.

I am happy with what I have done, the truck runs cooler, it performs better and I believe I am prolonging the life of the motor. If you take care of it, it will pay you back.

Any others out there with better results, I would love to hear them.

 

One thing I've noticed on several of my cars is as the tires wear down towards bald, my mpgs get better. As soon as I put in new tires, mpg drops a bit.

My truck is still bone stock, and I was pushing 16mpg on my stock BFG's before I put in new Michelin AT2-somethings. They were almost down to the wear bars; now I'm lucky to get 14mpg with about the same driving habits. That's about as bad as what I get on my 350. When my wife drives it with a lead foot on the gas and brakes, it drops to the low 13mpg's--hand calculated!

I know a bunch of you will scoff at this, but around town and local trips, I drive without my 100lb+ spare loading down the back. There's a small perceivable difference in acceleration... I honestly don't think there's much mpg gain, but technically speaking, that's 100lbs less mass to accelerate from each stoplight.

 

just a beep about a K&N be very carefull in putting the oil on because I have been seeing a marked amount of issues that when some guys oil them up they are using too much and that oil has been known to land on the hotwire in the MAF sensor causing all kind of issues surrounding driveability. there is a great MAF cleaner in spray form made by CRC and would be a good idea everytime you clean your filter to clean the MAF too.
* about tire inflation most of my customer air there tires for road comfort which relates to more rolling resistance i.e. less mpg. If you have a F-250 or above use the inflation spec on the sticker on the driver door and see if that helps to increase your MPG.
*one other player for MPG is to ensure that your temp gauge gets to normal operating temp quickly (usally the needle stays in the middle of NORMAL) if it looms aroung the 1st notch of the gauge it may be running too cold which changes the fuel mapping for the run condition. Most states use a different type of fuel blend for the winter vs the summer which you can go on line and get info on "blended fuels" or "winter gasoline blend" that too changes your MPG. Good luck