93 Octane is just a precaution in the M103 without a knock sensor. I have found that, in most cases 89 octane works fine. As the summer temps here in TX approach 100+ then I will occasionally hear slight pinging under moderate load in high gear on the highway. Then I know it is time to bump up to 93 for the remainder of the summer. As we move into winter with consistently lower temp weather, I switch to 87 octane which I continue to run with NO PINGING until the weather starts to warm up and the cycle starts all over again.

With regard to octane boosters, they do in fact work, but read the bottle carefully. One bottle is only good for a few gallons and you will find that you need 2 to 3 bottles to treat a full tank. After adding in the cost of the bottles, I'm sure you will easily surpass the cost of just going with premium fuel. Around here, the difference is only about 10 cents between grades. That's only about 3% when dealing with fuel prices hovering around $3/gallon.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280