Last fall our Department of Tax and Revenue Criminal Investigation Division guys went out to Ohio to learn about a sniffer that samples the exhaust to detect off road fuel, WVO and biodiesel. No more dipping the tanks. I am also expecting a crackdown on WVO and home made biodiesel this year or next if you don't pay the road tax on it.
Why else would you spend all the money for the sniffer if you can dip tanks with a 50 cent tube and catch off road diesel or WVO.

I don't know this to be in the works, but I have a gut feeling it is.

I have not been stopped by them this year yet, so I don't know if we are doing it by dipping tanks or the sniffer this year yet. I have confidence I will know in the next month or so though since it is getting warmer outside.