I've been looking for a coating that might extend the life of the rubber bushings, I guess motor mounts are just big bushings.

Pricey, but probably enough for several years:

https://www.gracosupply.com/3m-scotch-weld-ec-776-fuel-resistant-coating-quart-with-specs

data sheets:

https://multimedia.3m.com/mws/media/241258O/3mtm-fuel-resistant-coatings-ec776-and-ec776-sr.pdf

After reading the safety data sheet, I might not use it. But it is most likely an excellent product.

https://multimedia.3m.com/mws/mediawebserver?mwsId=SSSSSuUn_zu8l00x4xtvN82Smv70k17zHvu9lxtD7SSSSSS--


also this product might work quite well:

Liquid Electrical Tape

Liquid Electrical Tape - LET

I've contacted them to see if it would work to help protect the rubber against ozone & fuels. They think it will but they said they would check & send an email. If it does provide good protection to rubber bushings then they could probably sell a lot more if it was advertised that way.