I brought the truck from Texas back to Pa. this week (finally)!
I filled fuel at Loves in Dallas and added 4 gal. later that day. Drove a total of 578 mi. at an avg. 70 mph (interstate) , overhead said17.48 mpg, hand calculated 18.38 mpg

Filled up at Flying J in Missouri and added a treatment of power service. Drove 468 mi. at avg. of 74 mph and hand calculated 16.89 mpg ?

Filled up at Flying J, Drove home, 273 mi at avg. of 76 mph (up and down hills) hand calculated, 18.21 mpg.

Is it possible that the power service actually lowered my mpg? Being new to this deisel stuff has me wondering what I'm missing.

The Domie

 

I would assume it has more to do with driving variables. Your pedal input, headwind, tailwind hills, traffic, temperature etc. You may have also gotten some winter fuel as you headed north.

 

I wouldn't get too concerned yet. You sometimes get more foam from different stations and end up with a different liquid level which will throw off the calculated economy. I would run a few more tanks and keep your eye on the foam when toping off the tank. The differences you reported are similar to what I get when I don't pay attention to the foaming while topping the tank.

 

I'd figure that you got a bad batch of fuel, make sure to check your water drain off every other tank.

I've had the same thing happen in Bakersfield, best fuel I've had so far! Never had the mileage since!! $1.88 per gal must have been premium???.

All I know I got the best mpg yet!

 

Ok I'm new to this diesel way of life , tell me about this foam thing.

 

The foam just comes out of the fuel hose while it pumps in the tank. When the nozzle shuts off, you have to wait a bit and put the fuel in slowly til it comes to the top of the neck. Different stations have different pumps and nozzles and all flow fuel a little different. Now that you are aware of it you will see when you fill up your truck next.

 

Diesel will hold more air (foam) than gas. Therefore to accurately gauge a fillup is a pain in the ****. Dribble the fuel like a old prostrate soft dong. So far your patience is awarded with the average 17-19 mpg of winter fuel. Here's the kicker..........run a diesel tank say below half and it will start to foam by itself on the designed recirculating 3rd gen dodge. Air mixes in with the fuel flow below a half a tank and ruins the pressure/volume. Always keep your tank above half! Easier on the lift pump and cp3 and less chance of water vapour condensing in a half tank? Tell me again why yuppies drive a diesel truck?

 

power service helps keep the fuel from jelling in freezing weather,has no impact on fuel mileage.

 

N. Johnson, Thank god! I have no idea as to what you are talking about!!

Dribble like what.....?????

Sorry just could'nt help it!

P.S. I'snt foaming fuel detrimental to diesel performance?

 

Ok, let me try to understand this - - under 1/2 tank and the sloshing fuel starts to hold air and that is bad for the pumps and the mileage? Don't these tanks have baffles to cut down on this? What does how much foam you have as you fill up have to do with anything? You calculate by gallons used, not how much the tank holds, right?

Almost all of my driving was with the cruise on. The last tankfull was as described, in hilly areas.
I'm new to this deisel stuff and I want to try to figure this Cummins out before I start to tow the 5er all the time.

I can't figure why any yuppie would drive one of these things, they're a real pain in the ***, but that pain is really COOL!
Good thing they put windshields in these cummins, cause this smile could become a real problem going down the I-state!

The Domie

 

Don't Have Any Of These Problems.....

 

Fuel sloshing under 1/2 tank is not enough to cause foaming. The fuel tanks do not have baffels. The foam I am talking about occurs when you pump the fuel in the tank. The foam will bubble up the neck and shut the pump off early but when the foam settels out the actual fuel level in the tank is not really full. This will give you inaccurate calculations in MPG's. Different fuel stations will give more foam than others so you have to watch for this when filling and calculating MPG's. If the MPG's are up one tank then down the next and up again, it's probably due to foam while filling. Best way to correct for this is run 3 or 4 tanks and average them. That will be the most accurate. Hope this helps the confusion.