I dont know why I forgot to post this in this thread back when it was a question. Color sensitive paint. It comes in allot of different ranges. I picked up a powder that goes from white to black at 80f. Light blue went black at 80 when mixed with blue paint. The idea was tire temps but in 100 degree weather the purpose was not served. If I do it again I would get a pigment closer to 160 and see if that was the right temp range for watching the motor temp. I think the window on tires is too tight.