How long does it take for diesel to go bad in a parked truck?

I would say at least a year unless there is crap in the tank like water.

My beater truck sat for three years with a half tank of fuel before I bought it. Put a new battery in it then I drove it home, changed the filters a week later and haven’t had an issue with it, 1998 12 valve 465,600 miles on it as of this afternoon.

 

It depends honestly on a lot of factors. Conventional wisdom says a year. However, that is based on ideal conditions and is for the fuel to be as good as it will get. Diesel stored in such a way it has limited/no contact with oxygen, no algee contamination and in moderate conditions (70F or so) can last much longer then a year far more if stabilized before storage. The reverse is also true however. Diesel kept in poor conditions degrades much faster.

Also keep in mind just because the fuel burns doesnt mean its not having a negitive effect on your rig. How much and what that effect IS is hard to tell however and will vary from engine to engine based on factors like condition, age, build, maintaince and so on as well as the fuel itself.

 

Earlier this year, we pulled a ‘95 KW with a 3406 out of the fence row, had 1/2 tank from 2015. New batteries, quick shot of ether and she fired right up. Did a full PM, fixed the few things that were wrong, topped off with fresh fuel, tossed in 5 gallons of motor oil in the fuel tanks for good measure. No problems so far.

 

I've seen Fuel that Looked Like Muddy Water because it sat many years ...The Truck Ran without a Miss ...

 

This truck sat for almost 7 years. When I picked it up in Tacoma it still had fuel in it from nearly 8 years ago that the guy bought in Kansas on his way home with the truck. I drove it back with no issues and it’s hauling fuel in NE now with the same fuel filters. I imagine these days with bio fuel that the results may be different.

 

The fuel will last a very long time. The variable here us what type of fuel was in it. Because if it was a bio mix.....which ot of newer fuel is......it will attract water and grow algae. The algae thing is a big problem. It takes out your filters, clogs lines and grows in your tanks. It's also kinda hard to get rid of.

 

Algae and water always been a problem.

 

Well if it's Houston it takes 3 weeks for algea to grow. Unless you out cetane boost or Howes in it 50 miles before you park. I have changed out fuel filters a couple of time due to that. Anywhere else never had a problem parking for a month.

 

I bought a old White on time that had been abandoned out in the woods for 20+ years. Added some fresh batteries and the truck drove out on the fuel that was left in the tanks. So it will last a very long time.

 

Ive run 4 year old diesel in my old yacht.