I have an Excel spread sheet that started with my 2005 when I bought it. I always do a fill up, never a partial purchase and buy from the same pump unless I am on a trip. I keep beginning and ending miles from the ode meter to calculate miles drivers. I divide miles driven by gallons purchased. With each truck, I keep accumulation columns. So, with each fill up entry, I have mpg for what was used since last fill up and I have mpg since the truck was new. I check this with the computer in the truck and it is always extremely close. I also show where I purchased the gas. It has shown me twice that I do not want to uses a particular station again.

On the truck computer, I have never reset the efficiency reading so it displays my mpg since purchasing the truck. I use one of the trip meters to show average for each fill up. I record this on my spread sheet as well.

I don't drive for mpg as I like to get to my destination quickly but I do try to drive smoothly and I coast to stop signs and red lights as much as possible. I'm not **** about trying to get the most mpg, just curious about what is going on. My spreadsheet also will tell me if I am having a maintenance issue using more fuel. It was interesting to me that with my 2005 5.4, it never used more fuel as my spark plugs built up miles. Even with 65,000 on one set and 75,000 on the second set, there was no increase in fuel used.

 

im at 17.6 lifetime mpg with almost 50k on the truck.. That includes several ( atleast 6) 500 mile trips towing 7000lbs and a couple of evenings running down the race track.

With the stock size tires i popped off 20 to 21mpg every fill up and a few at 22mpg's on highway runs.. Around town was 18 to 19mpg..

Now with the bigger tires i'm around 19 highway and 16 to 17 city. There has been a few tanks recently where my foot was nice and heavy and i got 13 to 14mpg but that was pushing the truck hard day after day

 

LMMFELHSAO!!!

Late supper (Philly cheese steaks), and unjuns 'n mushrooms is a-shootin' outta me snoot!

 

And those were calculated by hand or based on what the dash readout says?

 

Every time I have manually checked my mileage, the actual mpg has been slightly better than the computer readout.

 

I drive moderately mpg oriented. Not ridiculously so. Rear end ratios matter, warmup in cold weather will gobble up fuel economy. Gas blends from one part of country to the other will vary. I do have oil changed at dealer, using Motorcraft oil, BG in oil and fuel about every 5,000 miles.

Calculate miles driven divided by gallons used. The computer has been conservative every time nearly. I don't think that an extremely slow takeoff is best for mpg. Moderate is best. Driving between stop signs every mile, moderately accelerate up to about 5 mph over speed limit, then coast down to stop sign. Set cruise on turnpike or highway when possible. Our morning commute is so early that traffic is light. That helps.

 

I have the 3:31 gears. I need to look into which ones get the best mileage and change them I guess. lol

 

If you drive more highway miles than town, the 3.31s should give you the best mpg. That is if you don't tow a lot. I have 3.55s and had 3.55s in my 2011.

It will take years in fuel savings to recover the cost of a gear change.

 

^^^ Ol' Jed's right.

Go to 3.73's, or better yet 4.10's, fer the fun-factor and towing proficiency, not any mileage benefits. Remember - ~$2K for a fer-by-fer. That's a lotta gayss, lol.

 

Unless you do like Bluejay does and keep a long running list my money is on the computer being right.

Look at the inputs for each and see which one has more chances for error.

Both use the odometer so that is a wash.

The computer uses the amount of fuel it tells the injectors to squirt into your engine vs the miles traveled. As long as all the systems are working properly this is a pretty accurate way to measure the mileage. Especially with the newer vehicle engine control systems that very accurately measure the air to fuel ratio.

The hand calculated way uses fuel put back in vs miles traveled. This too can be an accurate way but there are a lot more variables. If the fuel tank was a precise measuring tool such as a graduated pipette it would be easy, however, it's not. The shut off is dictated by air pressure inside of the tank. If your vent hose is not perfect, the shut off point will change. If the barometric pressure is not always the same, the shut off point will change. If you use a different gas pump, the shut off point will change. If the filter inside the pump is dirty, the shut off point will change. If you keep adding fuel past the first click you will skew your numbers. The only way to make this method accurate is to fill the tank to the exact same point every time and that's nearly impossible. Therefore, a hand calculation on one tank is a swag at best. If you keep a running total these small changes will even out over time and accuracy will improve.

 

Agree, my point is that the computer is as accurate as you could reasonably expect. Our miles are probably a 50% highway, 25% urban, 25% city split. I don't even know what my rear end gear ratio is, but the engine turns about 1,500 at 55. When you exceed 70, economy drops. Above 75, it drops more drastically. My observation is that the modern F150 has more towing capability, and as much payload capacity as an early 90's F250. Meanwhile, it averages at least 4 mpg better, and rides better. It literally has a much more massive frame that's stronger, particularly that section up under the cab. These are the good old days of power, efficiency, and capability.

Another thought: my truck is a 2 wheel drive, and if you have a 4x4, you can expect less mpg. Also, mine came with Michelin tires. I wonder if there is some variation depending on tire brand. Certainly wider tires hurt mpg.

 

This is by the readout, only reason i dont do every fillup hand calculated is because the computer is dead on to .2 off..

Just like this morning i filled up just from about half a tank. Computer read 12.1 gallons used and i filled it up with 12.2 gallons.

Here was one of my better highway runs where it shows the computer being very close to actual gallons used..

 

Tires make a huge difference. Yes, the OEM tires give you the better mileage unless you replace them with some higher efficiency compound tires. I replaced my tires on my 2011 with same size Toyo HTs and lost about 1.2 mpg. Never expected that. They were slightly wider and weighed 9 lbs more each. They were softer and handled much better but at a fuel cost.

Speed and headwind eats mpg as much as anything.

Get your axel code off the drivers door tag. That will tell what gears you have and if it's open or LS.

 

FWIW on the fuel mileage. I track everything.... I mean everything. I have tracked fuel mileage on every vehicle I have owned since summer of 2008 (11 vehicles spreadsheet method). I drive using common sense with an understanding of physics and the laws.

2010 5.4 4x4 3.55 SCAB 145" Wheelbase - Traded at 31k miles- Service MPG - 16.826
2012 Eco-Tooter 4x4 3.55 Screw 157" Wheelbase - Traded at 29k miles - Service MPG - 18.846
2013 5.Slow 4x4 3.55 Screw 145" Wheelbase - Traded at 21k miles - Service MPG -17.314

I think I might not track the fuel mileage on the new truck....

 

I'm betting your 6.2 F250 will average in the 12 to 15 range.