Caprang, something is not right. I know asking you about air/fuel filters is pointless. I also know that your tire pressures are right and your parking brake was not partially engaged.

What about the outside temp? Fuel additive? Winter fuel? Headwinds? Any sounds from your front/rear diff? Possible sticky brake caliper?

You ever see the Mythbusters show regarding fuel mileage in a pickup truck? They proved that the bed w/tailgate in closed position created a vortex of air behind the cab that actually helped the truck slip through the air with less drag than by driving with the tailgate removed or with a tonneau cover. You should check it out on their website.

I usually get anywhere from 12 down to 8 towing on interstate. 12-14 empty driving around town (45mph) and on two occasions driving on the interstates without a trailer I get 16 up to 18. Your 350 SRW should not be that much different than my 250.

Maybe you have a bad vacuum pump or a leak somewhere? You always run the A/C compressor?

I'm sorry man, I hope you find something. Bad 0xy sensor or something?

Try to get your hands on the Edge Insight. It gives way more info than you know what to do with and might raise an eyebrow for you.

 

I think if you guys filled your fuel tank right to the filler neck so you can see it and then go for a trip and then fill it back to that same spot so you can see it and calculate it by hand you will find a number that is quite different from the Lieometer ! It takes a bit of time to get the fuel all the way up to the neck,.... but thats the most accurate way to get milage !!! thats just my opinion !

 

Probably still selling winter fuel right now. Honestly I didnt pay attention to it but I buy from a Pilot truck stop. I added Stanadyne with my last fill up. I use synthetic oil, had the dealer check for codes before I got the reflash, I run 75 psi in tires. Truck only has 6k on it so air and fuel filters arent due yet. I have the auto climate control which I think cycles the A/C as needed and it was 49 degrees according to the outside temp monitor. It was early in the morning and there was no wind. I havent checked the lie-o-meter vs hand calc. since the reflash but I think since I used a 1/4 tank to go 100 miles its still pretty close.

On the way home it was getting windy and the temp was dropping as we drove. Started at 43 and it was 39 when we got home. According to the trees it was a cross wind. I can understand the drop in mpg due to this but I am disappointed that my best was only in the low 13's.

I wasnt thinking about any problems when I posted this. This is my first decent length unloaded hwy trip in a while so I wanted to see what I could do, all hwy, no weight, using the cruise control. I thought I could post a good number. I will have the trailer on it most of the time this summer so not sure when I will be able to run another 100 mile test with no weight. I got about 12 all winter with a mix of driving a little city, lots of country roads and 10-12 mile stretches of hwy. I expected to pick up more than 1 mpg but I will see what it does when it warms up more because I know the fuel and temp are big factors.

 

thatsme:

What ratio rear ends? Do you have a cap? Obviously I would love to get more mpg, it just doesn't happen. I have about 12,000 miles

 

"Truck only has 6k on it " Give it time.We are at 18K now. We saw a improvement at @ 12K then again at @16K. The new flash that we got here in Florida also looks as if it helped,. We are curious to see if we get better towing home. Oh We also added the larger air dam to our Job 1 build. Experiment on a long trip sometime. Start at 55 mph and run for 25 miles or so..then run up to 60 and do the same.. then 65,70,75. You will be amazed at the plunge in MPG as the speed increases. Same with towing.. As I mentioned on the trip down I.77, I 95 plenty of nice grades. Set the mpg o meter when we left and it said 10.8 when we arrived at out RV resort ..12000 miles. Over 22K total weight. We use a additive all the time and it does help..Need to keep that Centane level up.

 

rmosso1,
I have 4.10 gears!! No cap , open bed. I also run synthetic oil (motorcraft 5w40). I really think keeping the RPM'S at 2000 or below helps. However,sometimes I find myself going 70 to 75, not hard to do with these trucks as they ride so nice.

BTW I also use power service in the tank when I fill-up!!! Just over 10,000 miles

 

thasme:

Thanks for the info. Seems like our specs are almost identical. What is "power service" in the tank? Is that an additive? I do not use any cetane improver.

Maybe my foot is heavier than I think. As you know, one almost has to back off from a start to maintain less than 2,000 rpm's.

 

I have the crew cab short bed 250 and get 12 mpg in town and 13 on the highway going 75 mph empty. Since the last reflash it seems to have lost about .5 mpg but that may just be in my head. I only have 12,000 miles so I hope it improves but I wont hold my breath. I also thought I would do better on the Highway, I am sure I could if I slowed down to 65 but the speed limit is 75 and hard enough to keep it at that.

 

rmosso1,

Yes, power service is a fuel additive. I try to use every tank, but sometimes miss a tank. It does seem to help. I get it at Wal-mart, I think it costs around 16.00 for 32 oz.

 

thatsme:

Holy Crap! for $16.00 you can buy 8gallons of fuel! You better get better mileage than me! I would be awful careful in putting that much additive. We only have 38 gallon tanks on long beds, add in 32 ounces you have to be pressing the limit.

Serious comparison. If I put in 8 extra gallons. Say 30 gallons gets me 360 miles plus, the extra 8 gallons @ 12 mpg equals 96 miles, now back divide by 30 gallons as the real amount on hypothetical 456 miles gets me 15.2 miles per gallon.

Money or gallons, no difference. Now come on all you math experts!

 

Usually 32oz of power service is good for about 100 gallons. I'm sure he's not dumping the whole bottle in.

 

I'm guessing he doesn't pour the whole bottle in one tank of fuel

 

Let us all hope he is not using that much additive. thatsme, time to fess up and tell your buds! How much you usin? Damn, this sounds like something from LAW AND ORDER.

 

The additive isnt just about mileage either. Its supposed to help lubricate injectors and raise the cetane level for optimal performance. Ask the 7.3 and 6.0 guys about the ULSD, it has very little lubricant in it so a lot of those guys are adding supplements, 2 stroke oil or trans fluid to their fuel. It quiets the injectors down if that tells you just how little lubricant is in ULSD. Its not a requirement but Ford recommends the use of additive (their brand of course LOL)

 

Everyone also recommends 45 cetane which we cannot buy.