200 gallon tanks

I just moved into a 2018 Cascadia and sure enough I filled both 150 gallon tanks, drove 45 miles and the gauge went down an eighth of a tank.

 

Heck, full of fuel my truck shows 7/8 tank....

 

They are just an estimate really.

 

Every Freightliner I have ever driven has a 80 gallon diesel on the driver side, a 10 gallon DEF in front of that, and 90 gallon tank on the passenger side. Total capacity 170 gallons diesel, but even though I have been scared of my fuel level a few times, I have never managed to pump more than 145 gallons.

There is an air gap at the top of your tanks that is #### near impossible to fill. That gap across the whole length of both tanks is probably near 20 gallons of air that you will never fill with fuel unless you have fuel fill caps at the back of the tanks, and fill the tanks while the truck is on a significant downgrade slope.

 

Tank gauges are linear distance gauges. Your tanks are almost certainly round in cross section. (There ARE oval and rectangular cross section tanks, but I rarely see them.)

The amount of fuel per inch of height in the tank starts low at the bottom of the tank, and grows until you get to the middle of the tank, then shrinks again.

So, linear fuel guages are really just showing you the height of fuel in your tanks, not the actual percentage of capacity remaining. That percentage gets more accurate the closer to half a tank you are.

On flat ground, my truck gets about 200 miles in the first 1/4 tank according to the guage, and 350 or so for 1/4 to 1/2 tank. Then it gets about 350 again for the third quarter tank, and the bottom quarter tank goes back to around 200 gallons.

 

It varies by truck & installation. My truck activates fuel light when I have 40 of 140 remaining. My last few trucks also only measure fuel qty in one tank, not both.

 

it's only Freightliners that are notoriously inaccurate
Every Paccar (KW/Pete) pretty accurate
Volvo's, scary accurate

Freightliners, joke city

 

Get one of those mirrors on a stick. You can swivel it to look down in your tank and shine a flashlight. I have a swivel mirror in my tool box. It's indispensable for threading nuts on bolts when you can't look directly.

Rather than a stick, tie a bolt on a string and drop the bolt to the bottom. Use a zip lock to stow the diesel covered string.

 

The fuel gauge sending unit was one of the first things I replaced on my truck. Get somewhere below half tanks and the gauge would start going wild, "You're empty! You're full! You're empty! You're full!"

Frequently when I do drive away for oil field companies they have a single 110 gallon tank. Think about THAT! If you are pulling a sand chief, mixer, or fracking pump you can be up to 110,000 lbs gross weight and LUCKY to get over 3 mpg with a gutless 350 hp Cummins or CAT. Then add to that the fact that a good fraction of those beat up trucks don't have a functioning fuel gauge sending unit. Fortunately the tank is under the driver's door, so it's easy to look into the tank IF they don't have a ###### fuel theft cover under the cap. Then all bets are off whether you can make it 20 miles over dirt roads to the first available truck stop.

Running out of fuel isn't fun. Ten gallons is minimum. Then you need to spray starter fluid in the air intake and maybe prime the system if you know where it is on an unknown truck with long gone manuals.

 

Yeah right

Macks are the same as western stars which are the same as the kw I had.