I have a limited engine in my C320 and have been running reg, for the last two years. and just like the crossfire it requires 93 octane,. for the first tank or two the ecu is changing it's self to accept the lesser octane after that it runs great gets 26 mpg ,,weighs about 300 lbs than a limited crossfire,,, so to answer your question,,yes you can run reg 87 octane or 89 octane
don't forget for the first two tank fulls drive easy,,,not like i do . jim