You are fueling up with diesel, how full do you go?

Discussion in 'Questions From New Drivers' started by Labrador, Apr 15, 2024.

  1. tscottme

    tscottme Road Train Member

    So say the common sense to the OP so he then has the sense common to others.

    I'll say that when I filled my tanks I generally filled the tank to the bottom of the collar or neck wher the fuel cap screws on/off.
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  3. snicrep

    snicrep Medium Load Member

    May 13, 2009
    mcallen, tx
    I wait til morning just because I want to grab a spot.
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  4. gentleroger

    gentleroger Road Train Member

    Jun 1, 2010
    It is a valid inquiry.

    First off, on any car made after 2003, when the pump kicks off, that's it. Topping off isn't going to add a significant amount of fuel, and is likely just going to spill out. With the cars and pumps of the 80s and 90s, it's a different story. So from a modern perspective, it's "common sense" to not top off.

    Secondly, most fuel tanks (every cascadia) have "fill to 95% capacity " stamped next to the fill tube. It's a 100 gallon tank, so max of 95 gallons. How do you know where 95 gallons is? Is it the bottom of the anti siphon? The top? Somewhere inbetween? Give me a TI-81 graphing calculator and some scratch paper and I can do the math to figure it out, but that's going to take some time and I'll need a couple three Old Fashioneds afterwards.

    Finally, we should take into account all the half bits of stories new drivers pick up from their cdl school instructors. How many guys in this thread have mentioned over filling and spilling on the ground? As a new driver it can be hard putting all the stories into context and coming up with the correct moral.

    A couple months ago I made a run out west with another driver. Newer guy, 18 months or so. Not the brightest bulb but not a moron either. As we climbed towards Denver, his fuel gauge went wonky and showed him as empty even though we had fueled that morning outside of Omaha. It was just a pressure issue, but he was freaked out about it and was on the phone with maintenence. I just had him run his truck over to the fuel island and top off and we'd see what the gauge said. As soon as the auto cutoff happened, dude hung up the pumps. We then had a conversation about topping off and why it's a good idea. Then another conversation about winter blend fuel. Then another one about fuel compliance and maximizing rewards. Then the next day we had a conversation about fuel economy. Over the week we ran together, we had several conversations about things you or I would consider "Common sense", but common sense is dependent on a common understanding of the facts and realities of the situation. What was missing was "critical thinking". The guy I was running with had common sense, just not critical thinking skills. The OP here may have asked a silly question, but silly questions are usually some of the most important ones to ask.
    Last edited: Apr 17, 2024
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  5. Labrador

    Labrador Medium Load Member

    May 31, 2018
    I have been doing some googling and I think the volume of diesel fuel increases by about 4% from 0F to 100F. I guess it is not insignificant. 4% of 150 gallon tank is 6 gallons. The expansion is quite a bit more than I thought.
    Magoo1968, dosgatos and gentleroger Thank this.
  6. Labrador

    Labrador Medium Load Member

    May 31, 2018
    My truck recently had a fuel tank heater installed, the kind that brings heated coolant from the engine and it circulates through a heat exchanger. At the top of the tank there is a square 6"x6" piece of metal they have screwed to the tank and in the middle of that the coolant hoses is where the coolant hoses enter the diesel tank to go to the heat exchanger. The gasket between the plate and the fuel tank developed a leak about a week or two ago. I usually fill up in the mornings and start driving, so I would think there would not be enough temperature increase in the fuel ....ahhhhh ok it makes sense now. The air was not heating up the fuel the fuel is being heated by the tank heater. So I top off the tank, start driving, the temperature inside the tank rises from say 20F to 30F in perhaps 10 or 15 minutes of driving. It may heat up enough so that the expansion of the fuel occurs faster than the fuel is being used in the tank, drives up the pressure in the tank and blows the gasket. But isnt there supposed to be a breather or some kind of pressure relief in the fuel cap?
  7. tscottme

    tscottme Road Train Member

    I spent maybe 5 years trying to get maximum fuel points while I worked nights, I drove the EXACT same trip every night. I shared the truck with one other driver going to the same customer when I wasnt driving. As long as he reset the fuel counter & the trip mile odometer or I did both of those I could drive our truck down to the last 15 gallons in a 125 capacity AND I filled the truck in the same way every time it was refuled, by me. It was never sometimes fueled just until the pump clicked off and sometimes stuffed with every drop it could hold. I nightly compared the fuel added to the amount the truck fuel counter said was consumed and compared Avg MPG calculated by truck with the trip odometer & fuel ticket amount.

    I learned several things. The Volvo computer was nearly accurate for average MPG displayed on dash. The Volvo was very very accurate in its Fuel Burned total. It was ALWAYS within 5 gallons of the certified amount on the fuel ticket.

    If you want to check your truck you just need to be the only driver of it. Always reset your trip odometer & fuel burn counter when you fill-up, only fill-up in the same way every time, and compare what your truck says you will need to fill tanks and what your fuel tickets shows you added. Some trucks have a fuel burn totalizer and some don't. Many drivers never spend 1 minute in a year investigating the dash displays or the truck manual and just repeat stories they heard from drivers that last drove in the 1950s to 1970s and conclude "guessing" how many gallons you will need to fill up is too hard to calculate.

    In my last Freightliner, not my last truck, the low fuel warning came on when the Empty-Full gauge was showing about 1/4 fuel remaining. At that point it still had about 1/2 fuel remaining. Nothing above was using the Empty-Full needle gauge. Everything was referencing a digital number display buried a level or two in the Volvo display menu.You should learn your machine, but not assume NOTHING can be known. You can learn as much as you want to know, if you put in the effort.

    If I didn't explain my process properly, please ask questions.
    Last edited: Apr 16, 2024
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  8. High Stepper

    High Stepper Light Load Member

    Jun 8, 2022
    Square One
    When running high value pharmaceutical loads, you don't even have time to stop or people may die. So the only option is to fuel on the highway. You can't even have down time due to emissions.

    Fortunately I worked with the engineers at cummins to make a compatible fuel that could not only burn efficiently but also be injected into the 7th injector and heat up the DOC and keep the DPF filter clean. It was a combination of Red Diamond Sweet tea and naphtha, I can't disclose the formula because the patent is still pending.

    Enter @HoundDog7. He was not yet hazmat certified so we had to fuel surreptitiously. He spent hours training to fuel by playing Top Gun on nintendo.

    He would get in a vacuum truck and meet me on the interstate late at night and fill both tanks as we cruised side by side . It worked flawlessly. No placards necessary on this truck:thumbup:

    Screenshot_20240416-205724_Cut Paste Photos.jpg
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  9. Crude Truckin'

    Crude Truckin' Alien Spacecraft

    Oct 22, 2016
    North Dakota, Eh?
    to empty out that tank, would he just slip the clutch a little to spool the turbo, then dump it to get the front wheels off the ground? That must have been a sight to see!!
  10. Lav-25

    Lav-25 Medium Load Member

    Mar 31, 2018
    Thats what the fuel guage is for .
    200 gallons - half tank = 100 left .
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  11. Magoo1968

    Magoo1968 Road Train Member

    Mar 18, 2021
    St Malo mb
    On a related note back when I had my 2015 t680 I kept getting def quality codes and occasionally temporary derate.. I tended to top up def as high as I could because in Canada many stations are frozen in winter.. KW mechanic told me to try stopping when it clicked and my problems went away . Tank is heated and needs room to expand or it affected the def draw apparently. He also advised topping up every fill up to keep the crystals down in the tank. Once all our drivers started doing the same most issues went away.
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