I don't know if this has ever been mention before but I was in need of a funnel to put some oil in my Lycoming 390. The only thing I had was a 20oz plastic coke bottle. So I cut the bottle about in half and realized the threads on the bottle match perfectly with the threads on the dip stick tube. So I screwed it in nice and tight and had a great funnel that didn't run the risk of tipping or leaking. I now use it as my primary funnel. An added benefit is you can screw the coke bottle cap back on and the residual oil won't drip out.