When Hurricane Harvey hit the Tx. coast, 4 or more of the coastal refineries there shutdown premium grade production.

My '91 300-SELs owners manual calls for 91 octane. I have always run 93 octane premium as mid-grade in my area is 89 octane.

I had no choice but to run 87 octane and with each tank I added a bottle of STP octane booster. The car runs as good as it ever has going this route.

It's possible it would run OK with just the 87 octane gas. I have no desire to find out. As soon as the current tank is done, I'll switch back to 93 octane gas as it's once again available.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"