But really, I have to wonder about the low-compression motor needing this octane as well. As with anything Mercedes, especially from this era, it was engineering and performance at all costs. I don't think it's a stretch to presume in the days of the 126/124/140, if premium was the best one-size-fits-all grade to provide absolute protection of the engine in all environments, MB engineers would have recommended it, even though they may well have known 87 would be fine in most situations (of course, we are speculating). Bear in mind, those of you not getting pinging in these cars on 87 probably have engines in good condition, live somewhere below the mountain ranges, and don't drive at redline. If you're running a ragged example, or you do high-altitude or high-rpm driving, you're probably better advised to run the premium. I have a 32-valve M119 in my 400E, so I'd be afraid to run 87, but if I had an m103, I'd probably rotate 1 tank of 93 v-power for cleansing for every 3 tanks of 87.

I ran 93 in my Toyota Yaris when I went to the mountains recently, just because of the hard work the little motor has to do on the grades. It only specifies 87, but during hard shifting moves I have noticed some occasional quick pinging. So the lesson may truly be, hard driving, altitude, you probably need higher octane than sea-level granny driving, no matter WHAT your application