Unfortunately, premium is what is recommended for the 6 as well!!! However, lots of people seem to run mid, and once I didn't pay attention at a new gas station and put in regular - no pings. I usually run mid, with an occasional tank of premium and Techron. Still get about 22-23.5 on the hiway, and 19-20 around town, regardless of grade. I have heard the 400E (94) gets around that as well - what has your experience been?
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E