With the virus going around, I am finding plenty of time to work in my shop, and ran across this test I started on 18 March 2018. This is a final update of my Fernco diesel soak test. These parts have been submerged in diesel for almost 25 month. The final results are the same as in my last update . The plastic has hardened to the same hardness of PVC pipe, but has not become brittle. I could bend the parts with pliers, but they did not break.
For those that are curious about Silicone hoses, I also tested those. All references I could find state, Silicone is not compatible with Diesel. That is an automatic challenge for me, so I dropped some 3/8" reinforced Silicone hose into the jar about 2 month ago. Interesting result - the hose swelled up to 1/2" in size, but still had the same texture and feel as before. Definitely a no-go for Diesel.
Now if I could just find a substitute for the 802 radiator hoses!