Sup guys. So I bought this 2003 g35 sedan with 135xxx miles in poor condition and had a bunch of work done on it. Water pump, radiator, thermostat, timing chain, and a pulley have all been changed. There was no problem except for a worn out wheel bearing that I meant to change sooner. Anyways, I let someone use it and they’re telling me that the coolant in the reservoir is overflowing and leaking through an open space at the top, so slight overheating occured. Also, the “service engine soon” light began blinking so now there’s a misfire. I also found out she’s been putting 89 gas in the car when it requires 91. My guess is that the wrong gas caused a misfire, which is making the car overheat. Idk if that makes sense. What do y’all think?

thanks for the response. What would your diagnosis be? I still haven’t seen the car to see the code