I have an 89 190e 2.0 that has a little dial control under the hood (on the driver's side fender) that controls the ignition timing. It says "EZL-KAT" on it, and has (I think) 7 settings between N and S. According to a sticker under the hood, in the "N" mode (which is where my car is), timing is 8-12' at idle and 19-23' at 3200rpm. In the "S" mode, it's 25-29'... and in that position, I get bad pinging with Super Plus gasoline. Therefore, it looks like 17' should be okay for you, as long as your car doesn't make a pinging noise.
By the way, if anyone knows what the "EZL" stands for, or what would necessitate 29' of ignition advance (the "S" mode), please let me know. I'm assuming it would be if the car was run on leaded fuel?