I am wanting to put some Lucas Fuel Injector Cleaner in my car, but the filler neck won't open up when I insert a funnel. Do they not want us putting anything but gasoline in there? I can't figure out if the filler trap door is magnetic or what this seems odd to me, I just believe in putting in an additive to keep things clean from the start. Also it would be nice to pour in some Octane Boost since all we have here in Oklahoma is 91 octane. If anybody has some tips I'd appreciate it!