Is it against the law to drive with a full Jerry can (the new approved steel ones) mounted to a tire carrier etc.? A couple of guys at work told me that it was illegal.

 

Depends on the state you live in. I don't think it is illegal here in MI, but where you live it might be. It would be a pretty stupid law noticing the only reason you'd even have a jerry can is to carry extra gas in case you run out.

I have a steel euro jerry can that seals air tight. I'm gonna mount it to my roof rack next to my spare and see if the cops give me any trouble, odds are they won't be able to see it.