Not street legal oil? what the hell do they do? pull your dipstick and put the oil on litmus paper? I've never heard of a kind of motor oil you weren't allowed to run on the street. what's it got in it? Phosgene?
He probably means it doesn't conform to industry specs for on-road/highway vehicles, it probably has the extra zinc and other stuff that puts out a bit more pollution and is only legal for use in 'off-road' vehicles. But with a classic 340 I'm sure it doesn't make much of a difference lol...