CAR MODEL:
2017 Infiniti Q60 3.0t (Non red sport)
BACKSTORY:
The car has 78,500 miles on it. I just bought it. Test driving the car, revving it, etc, prior to purchasing there was no sign of this noise. Had multiple people listening to it. Even when the car was at temperature, everything was flawless.
I met again with the seller (incredibly genuine and nice guy, his wife drove the car and was getting an electric car) and that night, i was again making sure the car sounded normal, doing all of these little tests, i revved it again at operating temp with no engine sounds (i am only revving to 3-4k, not redlining it lol). Drove about 1.5hr home, car feels great no sounds. I pick up my friend and do a little lap, putting it in manual mode and brought it up to red line while driving one time. We noticed a knocking sound when pulling back into garage.
THE PROBLEM:
The sound is shown in the video and is when it sounded the worst. It is rather variable. Sometimes it makes a constant knocking, sometimes it’s more of a rattle. Oil was just changed a few days ago by previous owner shop and they had that shop do an inspection on all fluids and everything was fine.
The knocking does not occur when car is cold. Only at operating temperature above ~2.4k RPM. Sometimes (like in the video) it stops above 3k RPM, but one time it did it all the way up to 5k when i let off.
All service has been done at suggested intervals and at reputable shops, I have the receipts from virtually every repair and service visit all kept neatly from the owner. On top of that, this car has been babied. The wife was not hammering the engine 24/7, just gentle 15min drives to work and back putting about 10k miles per year. Other than knocking sound, car is in absolutely immaculate condition. As previously mentioned, I have the receipts/invoices they kept from virtually every single repair and maintenance visit they’ve ever done.
Oil has been running the manufacturer suggested 0W-20 for every oil change.
Also, the oil is still completely full, clean, and does not smell burnt as of a few minutes ago (i have checked every day, even after having car idling for a while and 2 easy, short drives).
The only thing the previous owner didn’t do by the book was that they ran mid-grade fuel instead of the premium fuel. So 89 octane instead of 91. Half tank when I got home with the car so I drove it 1 mile to gas station and filled other half up with 91. No improvement to noise, doesn’t really sound like detonation to me though.
SUMMARY:
This knocking sound, very inconsistent. Sometimes sounds like more of a rattle. Just started 3 days ago. After 2 ~1 mile drives sound hasn’t gotten worse or better. Previous owner had all maintenance done by shops regularly and on time. Happens when at operating temp on throttle above 2.4k rpm. Doesn’t happen when cold. Oil levels are still perfectly full with clean, non burnt smelling oil.
Any and all help is very much appreciated! Scheduled an appointment next Monday with Infiniti dealership. Most likely will just tow the car there.
EDIT: Added video, did not get added correctly in original post.