Commercial bio has almost no methanol content. Since this is the most expensive part of making the stuff they have ways to get all of the left over methanol out of the end product. I figure it just gives the home made stuff I make a little more kick so I don't wash my fuel to remove it. I replaced all the rubber when I started making it and have never had a problem with them getting soft. I used the "real" Mercedes fuel line with the stars because it is suppose to be tougher than regular fuel line but I wonder.