Regular RP vs. Long Rider?

[gradylaw]

Does anybody know the difference between Royal Purple Long Rider and the regular 15W40 other than the API ratings? I understand that you can't get a particular rating unless you apply for it. The stats on the respective web sites seem pretty similar. Are they the same stuff? Why isn't Long Rider on the RP website? I emailed RP a while back and the response was that Long Rider was just for diesels and RP 15W40 was for gas or diesels. Nothing more. Is that a marketing thing or are there material differences?

Just curious.

Thanks for reading.

 

[Jeff Knight]

I'm also interested to know if there is a difference. Hopefully someone will know. Jeff

 

[gradylaw]

Anyone? ... Anyone?