Aj06bolt12r

First of all 3.5 ecoboost does not get 23mpg highway. Maybe if you have the cruise set at 50 mph and there is no wind. Seriously that is the only way that's happening. Its really more like 20.5 if running around 65-70mph. And worse if faster than that.

Also the mpg rating the dash gives us all is not accurate. You have to hand calculate to know what MPG you are really getting.

Also the reason a lot of people think they are getting better MPG after a tune is because the tune modifies the factory fuel tables, and makes the MPG rating the dash shows you even less accurate. I bet most of them are actually getting close to the same MPG if they are driving exactly the same way.

DallasTXF150

Aj06bolt12r

Way to be specific

vulnox

I would argue hand calculating isn't accurate either. I never understood why people thought it was.

Let's say you have a half tank in your F-150 so you stop at a Mobil gas station and pump until it stops automatically. You do nothing more, you don't hit the nozzle a couple times (which you shouldn't do anyway) or anything like that. It takes 14.4 gallons.

You write it down in your little book, reset your trip, and drive for a couple weeks and are back to a half tank.

You now stop at a Speedway gas station and pump until it stops, and it takes 12 gallons until it stops.

So you take your 300 miles on the trip, divide by 12, and think you are getting 25 MPG.

Here's the thing, it took 12 gallons until the PUMP stopped. A completely different pump, at a different station, with different weather variables which contribute to differences in liquid volume, etc.

Maybe you could have that truck immediately put on a flat bed, taken to the Mobil you filled up at a couple weeks ago, and get another 2 gallons in until the pump stops.

You are basically assuming that the pump stops at the same point every time, that liquid doesn't change density at all based on weather, and that no other factors (pressure in the gas tank, etc) are causing it to kick off prematurely.

Sure, at worst with a well calibrated fuel pump and everything, you may only have 1-2 gallon variance, but that adds up. 300/12 = 25MPG, 300/14 = 21MPG.

Int he truck world, those two numbers are hugely different.

So that's why I just do not get why people are so Hell bent on believing the hand calculation over modern dash displays, which are usually based off actual information the engine is getting on fuel consumption.

Edit:
Also, if I am totally missing something above, let me know. This is something that has always bugged me. I have a hard time trusting the auto shut off on fuel pumps always hitting the same mark when I get gas because as probably all of us have seen, you start fueling a tank that is down to 1/4 and after 3-4 gallons it auto shuts off. You hit it again and it goes the remaining 10+ gallons to fill up. The shut offs just seem as unpredictable as the computers.

Now if you have a way to measure the tank down to the tenth of a gallon, that's the only real way to be accurate.

bigtome

I am that guy...

2015 F-150 XLT 4x4 SCREW 5.0L
installed cold air intake
installed cat back exhaust with resonator delete kit
installed tuner
I also have a backflip tonneau

ran 87 octane first tank - as that was the gas I had when installing the tuner
switched to 91 octane on the next two tanks (currently burning through 2nd tank) - switched to 91 octane tune

I commute city daily and am the errand junky on the weekend - not much freeway time - lots of stop and go

I am impatient and like the sound of my truck howling

True numbers... 15MPG average
when I get the chance for some freeway time at 65-75 mph - I am in the number range that is talked about above

i did not buy the truck to be a tree hugger and I knew what I was getting into LOL

I plan on taking it out for the vacation trip of about 300 miles and will hope to see the MPG crawl back to a reasonable level.

Spiky

Easier calculation:
Assume 15000m/yr, $3/gallon cost.

At 15mpg, you used 1000 gallons to go 15000m
At 17mpg, you used 882.35 gallons
Difference of 117.65, times $3, saved $352.94 per year.

Roughly 3 year ROI on $1000 upgrade cost.

This is what I do for a living. (find efficient ways of calculating things)

News in

If the pump automatically shuts off early when you're pumping, you would record that you used less fuel. Which would raise your MPG's if you're hand calculating. Yet every time I've hand calculated and compared it to the computer's average, I always show lower MPG's than the computer. This is true on any make or model that I've checked. I've never hand calculated a higher MPG than the computer shows. I doubt anyone has, would be interesting to know. For some reason, the computer MPG estimate always seems to be optimistic. Although over recent years the computer seems to have gotten a lot closer to what I hand calculate, within 1/2 mpg or so, so close enough. Older vehicles, the computer was off by 3-4 mpg. I don't really think the space 20 to 30 gallons of fuel occupies is going to change that much with the weather either...

vulnox

You are focusing on one event, if the fuel shuts off early, as if that is all that is involved in hand calculation.

The amount of fuel you put in the previous fill up is also relevant.

I will try this a different way.

Let's say you have a 36 gallon tank, and the pump auto shuts off at 35 gallons in the tank.

You drive two weeks, 300 miles, and the tank is down to 20 gallons. That means you used 15 gallons in 300 miles. You would only know this if you physically checked the tank though.

300/15 = 20 MPG

You go to another station and fill it up. This pump click off at 33 gallons. Again, you would only know that if you were able to actually measure what was in the tank.

But you write down that the pump shut off after 13 gallons, right?
300/13 is 23.07 MPG.

23.07 is NOT your MPG though! 20MPG is.

Now, I am not saying this happens every time, but the fuel shutoff by the pump isn't some magical device that always stops your fill up when your tank is 35 out of 36 gallons full.

So no, it still doesn't add up. Also, the temperature variation was just one part of the things I listed, I never said it would account for the entire value difference.

mechanicboy

Tune is your best bet. You know about gaps, so file up the ones you're comfortable with. Carry as little weight as possible, cheap you don't need, subs, spare tire etc. Read up on eco-kidding(for fuel economy), it will tell you things like keep your tire pressure high, drive slower, don't use your hvac, use electronics as little as possible, don't use highbeams, etc. A bed cover would probably help. Change your tires to the lightest, narrowest, lowest rolling resistance you can. Lowering can help, just go to where your comfortable. Run 100% gas.

News in

I understand what you're saying. But, like I said, I've never hand calculated higher MPG than the computer says. It's always lower, every time. I generally fill up at the same station and run the tank down to 1/8th. It seems like if hand calculating was prone to a wide margin of error, I'd wind up calculating higher mpg than the computer shows at some point, but that's never happened in my lifetime. The only way I can explain that is the computer readout must be optimistic. I figure marketing has something to do with that... I agree, the computer should be able to be 100% accurate, but that doesn't seem to be the case. They seem to be closer on the newer vehicles, but a few years ago, my hand calculations were 2,3,4 mpg off from what the computer said (on a vehicle getting 22 mpg hand calculated, computer would show 25.x for example). I'm not 100% sure exactly what the computer uses to calculate mpg either, so there may be some margin of error in how it's calculated. I should google it lol. Pretty far off topic here, but interesting.