I have a similar story. When I bought my place there were two 55 gallon drums of diesel in the barn. The guy who I got the place from had been ill for a long time, so the fuel had been there a few years when I moved here.

After a couple more years went by I decided, what the heck. I pumped some in my tractor. It looked good, smelled okay and after running a few tanks through the tractor, I burned most of the rest of it in my 240D.

I also would just run with it and keep an eye on the prefilter.

Good luck,