It's my first time posting but I have 07 5 with 163k mile it' has had plugs put in every 75k. When driving on the interstate at cruising speed twice I've been getting code P0300. The car is running great I have not felt or noticed any misfire or stumbling. Has anyone else had this problem?

 

I have a similar scenario. I have a Mazda 6 Gran Touring and I get the P0300 check engine light whenever the season changes..car runs fine, not sluggish, no misfire..took it in to have it checked and had plugs and fuel injectors checked, they were fine, to have something to do they cleaned carbon build up from the throttle body assembly.. couple of weeks got the light again when the fall temperatures hit.. after a few days, bout 5, it cleared.. drove to Florida.. check engine light came on.. after bout 3 days it cleared.. seems to come on when the car goes through large ambient temperature changes.. anybody else see something similar?

 

After chasing mine for about a year, I found the drive belt had a spot wear it was stretching and causing the crank to jump and set misfires, I replaced the belt and it now has 204k and the light has not came on since. Try to look at the belt I know the 4 cylinder use crank and cam sensors to monitor for misfires