This gets a little more interesting. If you recall in post #18 I uploaded a photo of a rock hard stiff Aerotrend clunk line. It was out of a tank that uses an 80:1 Amsoil mix. I just inspected and changed out a clunk line in a tank that uses a 40:1 mix of Mobil 2T racing. Both were changed out last year( around mid Spring) at the same time and flown many times each this past season. The Aerotrend that came out of the 40:1 Mobile 2T tanks is about as soft and flexible as new unused Aerotrend Easy Flex I have on hand. I will say that the plane with the 80:1 Amsoil was flown a bit more than the other but the 40:1 Mobil was flown plenty of times this past season. The only thing I can think of is either the higher content of oil or the differences in additives or lack of between brands is keeping the tubing flexible in the 40:1 tank. What do you think??[sm=confused.gif] Here is a photo of the still supple Aerotrend out of the 40:1 Mobil 2T mix tank.