I wish I could keep a log for my mileage. But I do to much city and highway on each tank it would never indicate correctly. Also my diesels tend to high idle a lot since its winter here. I also am towing and not towing a lot on the same tank of fuel. Mileage varies so widly you could never tell squat. I can get from 20 down to 8 mpg depeding on what I do.

 

i have to speak my expirence with this stuff. I have a 99f350 dually and was pulling a trailer cross country. I noticed that the truck started smoking a bit more then usual after downshifting (and on acceleration) after about 1500 miles of my trip (16,000+ weight) I decided to get a bottle of the Diesel Klean at a truck stop and but a bit in. The smoking went away but so did my mileage. I was getting about 300 miles per tank prior and then next tank i got horriable mileage, about 200 per tank with little change in terrain i was driving on. Can anyone come up with an explanation for that?

 

Possibly,
I'd like to toss an idea out here and see what kind of comments I get:

I'm beginning to think that temperature plays a role here. We all know that the flow rate of diesel fuel is greatly affected by temperature, correct? I wonder if the foaming rate is also affected by changes in temperature? Does anyone know if diesel fuel foams more during pumping when it's cold out?

I ask because I just finished my last tank load of fuel (city driving) and refueled yesterday afternoon. Mileage was only 15.1 mpg. I was expecting a higher number, especially since I got 443 miles on this tank of fuel but it took over 29 gallons to fill it up. (which seems weird because my tank is only supposed to hold 29 gallons and my fuel guage still showed I had 1/4 tank left).

I filled up at the same fuel station (even the same pump) that I used when I got back from El Paso this last trip (when I got 21 mpg). However, that evening it was fairly late and fairly cold when I refueled. Throughout this mileage test that I've been doing, I've always refueled by setting the pump handle to pump diesel at it's slowest setting to minimize the foaming as the tank is filled. That night, the pump handle "popped" at around 12 gallons...I continued filling manually and got about 3 more gallons in before I deemed the tank to be full. Yesterday, the pump handle "popped" at around 22 gallons, I manually filled a little more than 7 gallons more! Yesterday was quite a warm day here.

Perhaps my tank wasn't completely full that evening I returned from El Paso? Maybe the cold caused the fuel to foam and I really should have been able to get an extra 2 gallons in the tank. That would have been about 18.5 mpg instead of 21 mpg. Throughout these trips to El Paso and back, all the fueling was done around mid day, except that one cold evening. I could be way out in left field here....but if diesel fuel does foam more or less as the temperature changes, then this would account for all the variety in fuel mileage reports from diesel owners. It would explain why my final trip appeared to net 21.0 mpg and why my last tank of city driving wasn't anything special (15.1 mpg compared to an average of 15.0 over the last 2 months).

I'm going to Phoenix tomorrow. Of course I'll continue checking my mileage (no DFA in this tank). I'll be returning late in the evening, I have a Conoco about 1/4 mile from my house. I'm going to fill up, drive home and park. Then drive straight back to the station around noon on Saturday and see how much more fuel it takes. Should be interesting.

I'm crazy huh?

 

There are two things to consider: the tendency for the pump to "click" and shut itself off is dependent to a degree on the other people pumping fuel at the time. If other people are topping off their tanks, and their flow of fuel into their rigs is a short staccato of bursts, I've found that can trip my pump into shutting off before it's time. When alone at the pumps, I get a much more consistent line pressure, which allows me to get a smoother flow.
The other thing, since diesel fuel foams so much, is that for the purpose of mileage checks, I always take the time to trickle fuel into the tank to get as much fuel in as possible. I will fill up until the fuel is actually within 4-6" of the top of the filler neck. Often, once you've reached this point, the fuel will drain down into the tank enough to add a little more. Though it's tedious, you can be absolutely sure you're getting the maximum amount of fuel in. The amount of additional fuel that can be put in is quite amazing. Depending on the conditions outlined above, it's not uncommon for me to get an additional 4-5 gallons into the tank once the pump shuts off. Couple that with the inaccuracy of the fuel gauge on the truck, and I've found that my 19 gallon front tank will actually hold 22 gallons, and my 18.7 gallon rear tank will hold 21.
I would think, for absolute accuracy and consistency, you'd need to be sure you're starting with the same amount of fuel in the tank for every test, and to me, the only way would be to top it off as described above.

 

Yeah so much depends on fuel...I went on a 600 mile trip to lincoln NE last weekend with 10,ooo# behind me, stopped at same stations each time for fuel, and there was 2 mpg difference between phillips 66 diesel #2 and Total diesel #2, total being the better fuel of the two mileage and power wise. I added Diesel Kleen to the first two tanks and left the last 2 without it and actually had WORSE mileage with DK in the tank but that could be contributed to the fact that there was a slight headwind going out and no wind coming back and also it was colder going out than coming back--mileage was worse on my way out on both tanks.

So many variables, trying to track mileage differences between tanks is like picking gnat***** out of pepper...

 

(Digging out college text book)
The colder a liquid is, the more dissolved air (or any gas) it can hold.

Like a warm coke or beer goes flat, the fizz goes away.

And diesel fuel would tend to hold more air bubbles when it's cold and release the dissolved air when warm.

 

Thanks Paarrothead, this confirms my suspicion. I filled up my tank Friday evening as full as possible. Since my filler neck has one of those pump baffle pieces in it, I can't see when it's full until the fuel nearly pours out the filler neck. But I filled it all the way up anyway....like Quadzilla mentioned, it takes a while. But eventually I got there, completely full, no visible foam, actual diesel fuel all the way up to the filler cap. I drove .3 miles home and parked it for the night. The next day my family and I prepared for our drive to Phoenix I drove .3 miles back to that same station and was able to get 1.1 gallons in the tank so it was at the same level as the evening before. So, some "settling" must have occured.

338 miles round trip, with a small trailer and 700 lb motorcycle on the return trip @ 75 mph yielded 15.7 mpg. Sunday morning, I fueled up the same way and made the same trip to return the motorcycle and bring back the empty trailer. Two identical trips at 75 mph. Saturday was straight diesel with no DFA. Sunday I ran DK again. My mileage on Sunday was 16.9 mpg. I think this is a better guage of the DK effect because I made SURE my tank was ful when I started and when I returned. Plus I filled up at the same time each day in case that matters any. I normally wouldn't fill it up all the way to the cap, but I new I was going to be on the road to start burning fuel, so I figured it would be ok.

Does anybody know how accurate the fuel pumps are? I've always expected them to be very accurate because it's how the sale is measured. I see inspection stickers on them all over town, but what do they inspect exactly? If diesel fuel foams so much, how do we know we are getting a whole gallon when it pumps a gallon?

 

I still have my suspisions about the orignal thread and think maybe, if the boosters used were in a different order, you'd get the same results. This would be due to the fact that the product had cleaned the fuel injectors and that "benefit" continues till they start to gum up again.

I use DK every other tank full and like the smoothness of the diesel engine and can see and hear a significant difference in the engine when the tank has the DK in it verses when I am running w/o the DK. I have just over 13K on my 7.3 now and I suppose due to engine break in and DK, my mileage has climbed to 17.3 from 15 in town. In town is my normal mode of driving. I believe this is significant increase especially since it is now winter and the increase in mpg is higher. I think I can expect better mpg when the weather finally warms up.

Except for the quieter and smoother running engine, I'd probably skip the DK additives as I see no real advantage cost wise adding verses not adding any. But as long as my engine keeps humming and sounding great, I'll keep using it every other tank. I have never tried any other additive and will have to check out them soon.

Thanks for sticking the thread.

Doug;}

 

Agreed. Running the DK first and the Rotella second may have performed just as well.

On a different note....I was talking to our fleet manager about various DFAs. The diesel drivers all have their favorite additives which they use from time to time. It's either feast for famine for the DK users....about half report increase in mileage, power and general drivability. The other half claim a reduction in mileage.

 

Those that report a reduction in mileage might be feeling the improved performance, and driving more aggressively. That's probably why I haven't seen an improvement in my mpg since I added the chip and propane.

 

Thank you for the info...

I'm a new Power stroke owner, 8 weeks

Some thing to remember when fuel gets cold it shrinks. That's why when the fuel is cold you can hold more in the tank.

I'm going to go out and buy some tomorrow and try it. I installed a bulldog chip and a APE air filter and a 4" exhaust. The salesman said that I should get 2 to 4 miles better milage. My milage went up 2mpg and it runs a whole lot better....

The funny thing is my computer says that I'm getting 18.5 and doing the trip/gallons used 15.1...

GChavas is your truck a 2x4 or a 4x4??? Mine is a 4x4 and is this avg for a 4x4???

Thanks DR JOE

 

Welcome to FTE DR Joe and I hope you enjoy your PSD as much as the rest of us. Sounds like you are off to a good head start. My truck is 4x4. I went through two tanks of fuel during the past 9 or 10 days, all city driving 35 to 45 mph speed limits. I didn't run any DFA, and I made sure I topped the tank off each fill up. I got 16.2 mpg and 15.2 mpg on last two tanks. I had lots of "Turbo Time" on the last tank...so I was glad to see that my mileage didn't suffer too much. I've kept fairly good fuel logs since I bought my truck and I'm getting better mileage now in the winter than I was getting in the summer (before I tried any DFA). I was averaging 14.4 mpg city driving (mild foot) before I started this test. I think my engine was full of deposits in the fuel system and using the DFA has helped clean things up and allow the engine to perform better. I'm sure there is value to using some type of DFA, I like the DK product because I noticed immediate results, plus it smells something awful....so it must have some pretty powerful chemicals in there.

I think your onboard computer is reading fuel mileage incorrectly because of your aftermarket chip. I've heard similiar comments on other posting in this forum.

 

im running 01 350 with 90000 on it now. bought truck used and started using diesel kleen grey bottle and got very close mpg as you have. driving 75mph 16 to 17mpg slow down to 65mph i get
21to22 really love this truck.

 

Good info, now I want to see a comparison of the Stanadyne (Performance blend) vs. the diesel clean.

 

Me too. I'm going to try and set up another couple of runs to El Paso so I can test out the two different brands. May not happen until next month though.