Just went into to PB today to "look around"...they carried both Formula Shell and Exxon Superflo for about $1.79/qt, but the Shell was SL while the Superflo was SM. I've read these may be pretty good dinos, in case I run into a shortage of TropArtic I'd be looking for one. Besides Havoline, how are these two oils, and should I be concerned with the SL rating for an '02 vehicle? They also had a store brand (ProLine?) for $1.49/qt, and it was SM rated, but the bottles didn't say who made it. Thoughts???