2002 F250 I have been getting 12 - 14 MPG and so addeda can of STP engine and injector cleaner. I went 110 miles befor it came off the full mark and got 21 MPG on that fillup now I'm back to about 16MPG. Did the computer see something different or did that can of STP treatment up my octane??

 

I don't know but Diesel fuel has a Cetane rating not octane. Try it again, but i think what you used is for gas engines.

 

No it was for diesel.

 

Ok try it again and see if MPG go back up. It must be working.

 

Are you using the computer or calculating by hand. Just curious

 

STP - Diesel Fuel Treatment & Injector Cleaner here is a link for what I used.

 

By hand . filled up two clicks of the shut off did the same at fillup took milliage and divided by gallons. The thing that suprised me was that the guage stayed on full for 112 miles. So I know I was getting better than average milliage.

 

Well sounds like I need to try this stuff I havent seen much difference in mileage with diesel kleene

 

I think what you need to try is filling your truck right up to the top before you come to any hardcore conclusions.

It takes 10 minutes or so to top the truck right off after the pump clicks (unless you have the harpoon mod).

The injector cleaner probably helps, but its hard to see that it would help that much.

 

Welcome to FTE, wingerpaul! Stick around and you'll see a great bunch of guys here in our little family that are more than willing to help out and advise you (generally very wisely) in how to take care of and optimize your truck.

Here's another question for you. Did you use the same station AND the same pump each time you filled up? If not, "two clicks" from one pump/nozzle to another is not a valid comparison due to the varying levels of sensitivity from nozzle-to-nozzle.

preppypyro is right (his comments below). If you want dependably accurate mileage results, you need to fill up until you can see liquid fuel in the filler neck... not foamy fuel... pure liquid fuel, and it will take you a while to get that if you have not harpooned the tank yet. HOWEVER, by filling up until you can see the liquid, you will then get absolutely accurate mileage counts as long as you do it that way every time. BTW... most everyone in ehre refers to the truck's mileage computer as the lie-o-meter because it generally overstates your miles per gallon - but there are a few members whose driving habits and conditions allow the computer to be right most of the time, but only a FEW.

Regarding the 110 miles until your gauge needle moved off FULL... well, that's why I question the accuracy of the "two clicks" method you used. You see, I have filled my tank exactly as I described above for EVERY tankful over two years, and 80% of the time at the same pump at the same station. Here's the point... Every time I fill up, whether driving city or highway, it will always take at least 100 miles before my needle moves, generally takes 110-120 miles before it moves, and on a long highway ride when I'm behaving myself, it will take as much as 135 miles before the needle moves.

Just for a little more context on how frequently I fill-up, I average nearly 24,000 miles per year on my truck, which is a whole lotta fillup events on my little 28 gallon tank.



As for fuel additives and injector cleaners, I would recommend any of the following.... Diesel Kleen, Stanadyne, Schaeffer's DieselTreat, Opti-Lube XPD, or biodiesel.... biodiesel will knock your mileage down a tad, but is the best lubricity agent you can find for ULSD fuel.

 

Mine does the same thing as far as the gauge not moving for a long time after a fill. If I stop for a break then all of a sudden its at 1/4 tank.

 

Mine doesn't move for a long time either... but I have a 55 gallon tank on my truck. I like to refer to it as "Exxon Valdez"

 

i get about a 100 miles to a 1/4 of a tank im startin to wonder if something is up

 

i go 150 before my needle starts to move. these guys are right, unless you are filling up completely (you see it in the filler) your calculations are bubcus.

it probably does help, as does DK, but until you get an accurate reading- you are in the dark as to how much.