When does diesel go bad?

[GaryKowal1]

I own a Marine yacht Service Company. We come up against old diesel all the time. Not Unusual to see a boat with diesel that is 10 years old. In most all cases it still Burns fine. Sometimes we have to polish it (filter) to get the algae out of it that has grown. Sometimes we have to drain the water that has accumulated at the bottom of the tank. But that old diesel still fires up the engine fine. Gasoline last a year or two before trash is your carburetor or some other part.

[MRUSA14]

The most important thing is to always store your rig with the fuel tank(s) full. This eliminates air space in the fuel system that produces condensation and water in the fuel. Water in the fuel leads to algae. Algea is what creates most of the problems in fuel in storage. No air space>no condensation>no algae>no problems!

[geordi]

Originally Posted by Crasher

What you are saying is that the burned ok, but by sitting too long, something developed in the fuel that will plug up the filters. What contaminated it,,,,, algae, bugs, ??

Yup - the fuel burned just fine, but what poured out of the filters looked AWFUL. Rusty brown color and slimy / chunky.

[Ivylog]

In the 80’s fuel shortages I ran 10 year old diesel in my heavy equipment without any problems. I recently cranked up a GM 6-71 engine by only putting a fresh battery in the truck that had not run in probably 10 years. One turn and it cranked and it aired up and I was able to move it out of the way. Some days you luck out... on it airing up, not the starting.

[awol50]

Sometimes depends on outside temps in storage. High heat for extended time is not your friend.
A completely full fuel tank is your friend.

[Roadfrog]

According to all documentation I've read, diesel will hold up for at least a year or more. Use a biocide and you shouldn't have any concerns. I use Biobor. One container will last you years.

[miketo]

Q: When does diesel go bad?
A: When it grows up in a dysfunctional family in a tough neighborhood.


But seriously folks, yep -- keep the tank full to minimize airspace. If you're a boater you're more likely to get bad diesel from a little one-hose place up the Inside Passage than from your on-the-road rig. Otherwise you should be fine. At least you don't have to worry about semi-regular tank cleaning and fuel polishing. Somewhat like GaryKowal1, I maintained a fleet of 30+ charter sailboats in Seattle for four years. Saw lots of bad things, seldom saw bad fuel or dirty tanks. Drain off the water and a quick filter change and things were right as rain.

[Triangle Drifter]

I have been using https://www.amazon.com/Biobor-JF-Die...s%2C184&sr=8-1 for many many years. Typically added to fuel, full tank, and run through the system prior to storage. Most storage periods are well in excess of six months.

[JohnBoyToo]

I've used no additives and just tried to keep a full tank when stored...


Only time I had an issue with diesels in any of the 3 pickups, 3 Ford Excursions, and two motorhomes was when I filled up before loading up for a trip in our Excursion and the station had water in the fuel :(

[tuffr2]

A Google search says diesel will stay good over 1 year.

But I would worry about DEF as that goes bad sooner. It will crystalize in about 6 months I think.

[Cincy Steve]

Originally Posted by tuffr2

A Google search says diesel will stay good over 1 year.
But I would worry about DEF as that goes bad sooner. It will crystalize in about 6 months I think.

You should have continued w/your Google search:

What is the shelf life of DEF?
The shelf life of DEF is a function of ambient storage temperature. DEF will degrade over time depending on temperature and exposure to sun light. Expectations for shelf life as defined by ISO Spec 22241-3 are the minimum expectations for shelf life when stored at constant temperatures. If stored between 10 and 90 deg F, shelf life will easily be one year. If the maximum temperature does not exceed approximately 75 deg F for an extended period of time, the shelf life will be two years.

[F76Marion]

I can promise you that most of the above is true. I am licensed ship's engineer (USCG Chief Steam or Motor Unlimited). The big issue with old diesel fuel it that, while the fuel won't go bad, it will support biological contamination. Virtually all proper diesel fuel systems will prevent this from damaging the fuel systems, but major filter issues should be expected.

In my trade, most vessels have "stripper" line in the fuel tank that draws off the very bottom of the tank. This always yields some nasty stuff. Few if any vehicles are set up with such, but if you are concerned, see if the people that really know your chassis can tell you if this can be done without great expense. Often a probe can be put into the tank by removing the level sender.

The fuel polisher that Gary Kowal mentioned is a pump and a set of filters to collect the bugs and water that have accumulated in the system. If there is any water (there almost always is) that is where the growth will start. When the biological activity gets going, it also makes more water. That can also damage the system with corrosion. Most diesel fuel treatments are largely a biocide.

Frank

[Itchytoe]

Originally Posted by djc290

I fueled my DP last fall - with additive. It sat all winter, had planned some trips by now but with this Wu-Flu crap, its still parked. When do i need to worry about it getting algae or stale?

You filled the tank and put an additive in it. Assuming it's a diesel additive, it's got a biocide in it. Algae, or more accurately microbes are your main concern, but that's dealt with via the full tank and additive. Worry about it again in 2021. Even then, as long as you have fuel filters, which you do, start it up. If it starts, you'll be fine.

[garry1p]

If diesel fuel was to age out a lot of farmers would be out of luck some equipment is only used a few week a year.