I talked to a friend of mine who owns a company that services pumps and tanks for gas stations and he told me that they frequently have problems with 93 octane because not many people use it ($2.15 a gallon) and water gets in the underground tanks(if not properly sealed when filled). I Never thought about that but since those tanks get filled up less often the chance of water accumulating in the tank is greater. He told me that it could be a reason why my 560 SEL runs rough some of the time. Though I would share the info.

Jerry Atlanta

 

I've always made it a point to buy gas at the busiest station I can find for that very reason. I always burn 93 octane in my SL.

Also, take care not to buy gas the day the storage tank(s) is filled. Otherwise, you're apt to get stirred-up sediment pumped into your tank.