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?
Not For Street Use means it has enough "stuff" in it that it cannot pass the EPA testing or carry the "starburst" medallion. Think of it like race fuel with lead vs pump high test. I use Not For Street Use VR-1 in applications where the spring pressures and cam lobes need the extra protection. It's like the Gibbs and Brad Penn oil. I dont believe any of those carry the sunburst SAE medallion.