How much fuel do you really have left when that fuel light comes on

Now I realize that the op is asking about a warning light, but on my truck, when it's full it only shows about 5/8, and I can run hundreds of miles after it shows empty. I've fueled at that point before, and could only take 190 gallons on 2 150 gallon tanks, so even those 2 points are only reference.

 

Never trust a ( dummy) light.

 

This is simply not a truth. The pickup tube never moves and sits an inch or two off the floor of the tank, it's always in the same place. If you have enough trash in the tank to be contaminating filters then the tanks need to be drained.
I've removed and drained several tanks (gas and diesel) and have only seen one with any significant amount of trash floating in the fuel.

 

I understand what you’re saying, but there appears to be some truth in that the fuel lines are more likely to absorb dirt or debris when the tanks are low in fuel.

In my first year as a truck driver, I ran my reefer fuel tanks a little under 1/8” and while fueling, the reefer lines got clogged up with debris. I had to take it to the TK shop, and the mechanic said he cleaned out the fuel lines with air.

Now, in my case you can say I moved the debris around when fueling the reefer, but I have a feeling this could also happen on its own by simply driving around in hills or making turns in the streets where dirty fuel can be absorbed.

By the way, eventually I learned that the reefer is not supposed to be fueled while the engine is running, especially if the fuel tank is low. I must admit I still fuel it while it’s running, but I fuel in the lowest pressure setting until it’s about half full. 7 years later, I have not clogged it again.

 

Can't say I ever heard that when running reefer for 3 years. But then again, the companies probably didn't want to risk drivers forgetting to turn them back on.

Aside from disturbance causing an air bubble or stirring up debri, which would get sucked up upon starting the engine anyway if you don't wait an hour for it to settle again, why shouldn't you fuel with the engine running? What would make it any different from fueling with your truck (or car) engine running?

Just the general fear of an engine spark igniting vapors?

 

I’ve heard about not fueling with the reefer running a few times from different drivers, so apparently it’s being taught somewhere. It could be that there are other reasons why the reefer should be turned off while fueling, and it could be the same reason it is for fueling up trucks or cars. As I’ve said before I personally do not turn off the reefer while fueling, and the only few times I’ve actually turned it off was when the reefer fuel was very, very low. Other than that, I’m with you in that I don’t think it’s a good idea to be instructing drivers to turn off the reefer because they might forget to turn it back on.

 

I have 2022 Cascadia, taks are 100*2 . The light was on right after i left the dealer and filled the tanks with 115 gallons, 2 days later 121 gallons …

I was worried if the right side tank valve was closed , so i first filled up the right side got 60 gallons, left side got 62 … I will not drive until the end but , just wanted to know the diesel mileage, i cannot calculate . Because I won’t be sure next time how much I use …

If the tanks are total 200 , when the light comes on at least I need to put 170-180 gallons , right?

any idea?

 

It depends on the truck.
On one truck.... It ran out of fuel when the gauge was at 1/8th tank and no low fuel light.
One I'm in now. Light comes on. Got 60 gallons left.

 

You have to be careful parking on a low shoulder, or an angle when low. I woke from a Longer than planned nap once, and all the fuel went to the right tank. Created a break in siphon. I was able to get going after switching the shut off valve from “both” to “right”, and priming the filter. Freightliners leave s lot of fuel in the Tanks. Doesn’t mean you can acess it though. My twin 140s (which are the exact same size as those marked 150 for some reason) have only taken 220 gallons, that was after running out. So 30+ gallons are in the bottom of each tank. Every Trucks different. Depends on the float adjustment and how the gauge reads it. I’ve replaced them on other Trucks I’ve had. Changed the adjustments also to avoid running out. Gauge can’t be trusted, till you’re familiar with it.