A Service Engine Soon Light Just Came On - This isn't something that usually happens on 1998 Infiniti Q45

Is it possible that the Gas Cap wasn't put on correctly or I purchased some bad gas...this happened with my 98 Honda Accord and the service/check engine soon would go away eventually.

Asked by for the 1998 Infiniti Q45
You won't know the cause until you get a computer diagnostic.
Yes, it could be simple as a non-sealing gas cap, but it could be a failed sensor, a very reach fuel mixture - which could cause further expensive damage.
When the SES light on - get a computer diagnostic and repair your car accordingly.

1 more answer
Just had a fuel injection service