So I decided to just ride it out. One tank of 89 octane. Overall mileage (combined highway/city) on my '06 MCSa: 29.8. Usual Mileage on 93 octane: 31.6. Difference in performance: none that I could perceive. Pichup and accelaration: the same.

I won't do it again intentionally, but I am pretty impressed with the ECU. If it did anything at all, it probably lowered the torque curve, but then I am not a racer, so it was transparent to me.

For the extra $2.50 a tankful, I will continue using 93. But I will not be at all nervous if that is unavailable and I know that Rocinante is perfectly capable of using the cheaper stuff.

Now if I could just figure out how to keep the rear window clean!

 

I will be sticking with premium as well and as far as the rear window...well good luck on that one. I have learned to live with it so far! happy motoring!

 

Uh, window cleaner and elbow grease?

If you're talking about a leaking rear washer nozzle, it should get replaced by the dealer. There is a one way check valve that's supposed to be installed. someone around here said it was a manufacturer's notice that went to the dealers.

Had ours done as warranty work about two weeks after taking delivery.