and if they know what they are testing for, so do the ones supplying it to the ones applying it on the tires. they can develop a "blocker" and hides the substance being tested for. the "pro" fuel mixers do it all the time. they can mix a batch of highly illegal fuel and it will test negative for any additives.....ps....its not just about softening. there are potions out there that can do anything you want....harder, softer, more grip, less grip, stiff sidewalls, floppy sidewalls and the whole time, the durometer reads what it is suppose to. kart racing tried for years to stop it and basically gave up. any time they came up with an "unbeatable" test, one person beat it then everyone followed.