How accurate are the gallons in fuel tanks ?

I have 2 125 gallon tanks on my T680, and the most I've ever filled up was 175 gallons. You never know what kind of crud is still at the bottom of the tank.

 

Depending on the truck it might be a service call for losing prime. Most if not all modern trucks are self priming, but still. Not a good idea.

 

You want to be careful about running them low as debris normally sits in the bottom. You don’t want that stuff to get inside your fuel system or else you’ll have bigger problems.

 

I think the shape of the tanks and where the cap is located will determine how much fuel your tanks will take. My tanks are 200 in total, but I have never been able to fuel 170 in them. I remember seeing a chart that said that 6 gallons are “unusable” (stuck in bottom) in a 100 gallon tank. Then the tank says not to fill more than 95% capacity, but I really can’t even if I wanted to. My tanks are round and the cap is not located on the very top. It’s on the side.

Even if you could fill the tanks to 95% capacity, you probably do not want to because it turns out tanks have vents on the top. This vent will look like an airline and will hang on a side of the tank. If you fill the tank to 95% capacity, there is a chance the fuel will spill through the vent airline when driving through an upgrade or downgrade.

 

Fuel gauge=FOOL GAUGE.

 

Your pickup is at bottom. besides, when your tanks are half way full, you can see the bottom of your fuel tank clear as day if you think bottom has crud

 

Isn't the pickup tube always taking the fuel from the bottom or does it change it's level with the fuel level in the tank?

 

I think you’re right. The problem now that I remember is fueling when your tanks are very low in fuel and your engine is running whether it’s on your truck or your reefer fuel tank.

When I was a rookie, I remember my reefer stopped working while fueling my (1/8 full) reefer fuel tank. I tried priming the fuel system as directed by the mega company’s Road Rescue department. I had to take the reefer to a reefer mechanic. He told me there was debris that had gotten sucked into the fuel lines while I was fueling. The moral of the story is to turn off the engine if you’re fueling your low tanks. You can also try fueling on the lowest setting until the fuel gets to about 35%, then fuel at max pressure.

 

I try to keep them topped off as much as possible, , especially if I'll be sitting for a while, and especially if it's cold. Any air space allows condensation, condensation=water