I am trying to figure out why my mpg isnt as good as everyone elses. before my mods i was at 11.5 town and like 13-14 hwy after K&N intake. 3X4 DP 5" exhaust no muffler or cat. 306,450miles runs and starts great idle can be rough sometimes, has plenty of power too. nothing ever changes the mileage though. my variable 10k mod(18k-10k)nothig changes even if i drive like an old lady. I ve tried all combinations i even tried the acetone add to fuel(ran smoother) tried diesel kleen(not any difference in anything. I tried the steve baz EOT mod to change timing and felt a difference but no up or down in mileage. The high pressure regulator o rings were changed and only made it idle better it has 3.55s and e4od reg cab stock 235 75 r16 tires. im usually empty too. So what else should i look into doing any suggestions? I am goin to be driving this truck to NC next fall for school so this winter i would like to get better mpg out of her.
---------------------------Jeremy

 

Well...306K is a bunch of miles, but if a compression test shows good cylinder sealing, and 3.55s with stock tires and usually empty, the only thing I can think to ask you is, do you have the bed covered with a camper shell or tonneau?

That tailgate acts like a parachute, as far as aerodynamics go, if the bed is not covered or you're not using a net instead of the tailgate. You can see in my signature that I have a big version of the F-350. I use a camper shell and my combined city / highway mileage is 16 - 16.5 mpg. I commute daily with the truck by highway and city streets so it's difficult to say what the mpg is for city and highway separately.

The only other thing I can think of is you have your foot in the accelerator more than you realize. If that isn't the case, try covering the bed and see what happens.

 

I have read just the opposite, the tailgate doesnt act as a parachute. Air gets pushed towards that cab and creates a "bubble" effect that allows air to roll over the tailgate. I have tested my mileage a couple times running with no tailgate at all and there was not difference.

jboard pump up those tires and keep those filters clean. I do understand your frustration having 3.55 gears and only getting 13-14 mpg. With my 4.10 gears the best I have seen is 21mpg, but that was going like 55mph for a few hundred miles. I have been told to keep those rpms below 2k, but at 70mph mine will spin 2500rpms.

Also the diesel kleen should have helped mpg, when I use it I notice less smoke and 1-2 mpg better.

 

The bed isnt covered but i will be within the next month...Would injectors cause this prob cause ive only had the truck for 6 months. and im not sure that the old owners ever did anything with them, but as far a compresstion goes i dont think its low cause the truck fires right off even cold and no smoke at all.
------------------------thanks, jeremy

 

When you drive at cruise what is your average speed?

 

Do you know if they are the original injectors?

 

id bet they are. get some new ones. you will probably see drastic improvements.

my case i went from 13 with 140k stockers to 16 with 1's. and that is 70 mph at 2400 rpms with 4.10s and 33's, crew cab and 4x4.

your truck will run much better.
my .02
post#2929

 

ok so where should i get injectors? money is tight so where can i get the best bang for my buck? what are 1's?
----------------thanks, jeremy

 

Beans Diesel Performance dot com. I think they are having a sell now, about $775 for a set of reman Stage 1's. Stage 1 injectors flow 160cc, stock about 95cc. You can get Tranny savers and reman stock for less. They are really good guys and have a good product and good service. Alot of poeple on this and the other site run Beans injectors.

 

if $ is tight just have him rebuild your stockers back to stock specs. dont want your tranny to get toasted. $ is tight for all of us right now. x-mas

 

I might have missed it but other than you 10k flip that you made I don't see you mention a chip or a tuner either one would improve your mpg.Dave

 

ok thanks, i would get them rebuilt but the truck is driven every day my only driver so i cant send the injectors away cause i gotta have my truck. Those 160cc arent gunna hurt anything like tranny or engine? if i go with stockers will they get better mpg than with stage 1 160cc? Im not lookin for any more power than i have just better mpg.
thanks, jeremy

 

Beans will do a swap out. You order the injectors that you want, you pay a core charge, they ship you reman. injectors, you pull your old ones, install your new ones, send them your old ones, and they refund your core charge. The only down time is the time it takes to do the injector removal/install, this is what I did and I was only down one day.

With new injectors you should see an increase in mpg. The largest injector that I would go with when using a stock tranny would be the Tranny Savers. You throw to much power at the stock tranny and they have a habit of dying early deaths.

Call Beans and talk to them, they are good guys and can answer any injector related question that you might have (increase in mpg, what size, price, benefits, etc.). They will answer your question straight up and will not try and push a product on you. Just my .02.

 

An observation that I became aware of today and I thought I might share it with you.

I put fuel in the truck and went to calculate the mileage and was surprised to find that it was 12.1`mpg. What! I thought. That is the worst I have ever had on any 6.9 under any conditions. This is a new engine too.

Well, after a few seconds the shock to wears off and I realized that the speedometer cable was having problems and that was reflecting the readout of the mileage meter.I have been trying to remember to order the damm thing but forget every morning.

At first I thought that the lube was gone and it was sticking, but, when I took it off from the speedometer I noticed that the plastic end of the cable was not square anymore but pointed like a pencil.

Well, that is the observation and I thought you might find it of interest.

P.S. For the last 5 mos. I have noticed that my milage would vary greatly from 13.5 to 17.5 mpg. I guess the cable has been going out all this time.

Wishing the best of the Holidays to all however you celebrate them.

Ed Tavas.

 

1. Start with a compression check on all cylinders, so we know what we are dealing with here. A low compression engine will get poor fuel mileage.

2. What tires are you turning? Are they tall and narrow? Short and wide? What kind of thread pattern? Is it an aggressive offroad style or a good highway tire? Just because you are running 3.55s doesn't mean much if you are running a short tire. A tall narrow tire will change the ratio considerably. Tire pressure is important also.

3. What RPMs are you turning and at how many mph/kph? Does the engine feel like its floating along or is it working a bit?

4. Do you get a lot of headwinds in your area? You might be fighting the wind and not know it. Good aerodynamics come into play at anything over 40 mph. If you have a good tailwind, then let her rip but if you are fighting a headwind, then easy off on the throttle and slow down a bit. The winds are more important than you think when it comes to getting the absolute best fuel mileage. Not many folks think about this but its true. The previous comment about the tailgate is true. It does add a considerable amount of drag.

5. Unlock your front hubs on the 4X4, you don't really need to be pushing around a second axle all the time.

6. Check your brakes when you stop after a long drive. Put your hands on the wheel rims and check for excessive temperature. Use a glove at first, just in case you find a hot one. Brakes dragging can cause mileage problems.

7. There are lots of little tricks. I give it hell going down a hill because it helps keep up the momentum when I reach the uphill part.