Thats the issue Phil, the veg oil attacks the rubbers in the pump, my thinking/hoping was properly produced Bio would be okay but seems you are witness to it not being so
I am popping 400ml of mineral 2stroke oil in my fuel at the moment to replace the lack of sulphur in modern fuels and this could be the issue with Bio and veg fuels?
midlandgardencare , is your home genny using heating oil? I have read but not sure used hydrolic oil could be used to power some genny's but I would check before use that as gospel.