the computer will retard the timing so the engine will have less knocking or pinging.

Lower than recommended octane may have the engine run hotter, you may get poorer mileage and for sure less performance. My manual says only use a lower octane if Premium is not available then fill up with premium ASAP. I figure the German engineers know better than I.

__________________
Steve Danville
what i did myself.
CPS
rear shocks
MAS x 3.
SparkPlugs (twice)
Fuel pump & Filter
Window switch
replaced both failed horns with Honda horns.
Cleaned ERG Tube
Oil changes
Oil consumption Fix
Brake Pads
A/C Recharge
Anti-Freeze change X 2.
Front Shocks. Monroe. $90
Mercedes Warrenty Work:
Harmonic balancer,power steering clamp. Cat converters.Drive Shaft Bearing.s
Replaced Outer Lower Tie Rods and front lower ball joints at 156,000 miles