Temperature Sensitive Paste (or other material)

I want to have a fuel dip stick that is mildly flexible to pass a curve in the filler tube. I have tried the metal tape from a typical retractable ruler like most of use, and that works, but I cannot see the fuel level on the metal. I have tried blackening the tape with Pro Seal and a few other things that are fuel resistant, but have not found something readily available to use. I can't see the fuel level with anything I have tried so far. Some sort of thermal paste that changes color would be perfect if commonly available.

An ideas out there?

How about a length of small diameter nylon or ptfe tubing? You stick it into the tank, put your thumb over the end, and pull the tube out.

A small wooden chain should do the trick. Making it would also keep you out of mischief for a while.

Why not make one out of a older car transmission dipstick- those are usually pretty flexible and are usually 2-3 feet long? While your at it, I'd hit it with some "instant blue" or touchup bluing used on guns.

I think his problem is not being able to see the fuel on a metal dipstick - something I can relate to. I use a thin strip of wood for my tractor, the wet part shows up real good.

Oh, I can relate to not being able to see the line - heck sometimes its hard to see with ANY fluid, much less fuel. I've done the cold bluing thing on some dipsticks before- improves the contrast

I got to thinking, if the bend isn't too tight you might be able to shave a 1/16" piece of the side of a 1x4 (or 1xwhatever) that would be flexible enough to slide down the filler neck

Heat shrink over a piece of welding wire. You can bend it into any curve you like and see fuel on the heat shrink, it comes in many colors.