My girlfriend just bought a 99 C Class and not knowing you have to use premium, put in unleaded. She had to head directly to a wedding so she hit the interstate and it started chugging and knocking. She drove it anyhow. I just got to the car and put some octane booster in the tank and managed to rev it enough to get it in gear and whip it around the lot a few times to get it to mix up a bit. It’s almost underivable. We are still 60 miles from home. I’m gonna have her leave it here for tonight. Any advice? I don’t know what to do when we come back for it tomorrow.