Funny you mention that. We received an old Cat D8 that had about 100 gallons of 18-year old diesel in it. I removed about 50 gallons and noticed that the diesel was about the color of iced tea. I burned about 25 gallons of it in the 802a that I had during the ice storm and the generator didn't miss a beat.I've bought a couple of deuces that sat in a field for 12 years. I drained, filtered the fuel with a t-shirt and reused it in the truck. They ran without any problems. The problem is the build up of algae in the containers diesel is stored in. I believe diesel will last a lifetime if store correctly, just my opinion.