Hello. I recently made a deal with a friend for a 2007 Chrysler 300. It has the 2.7L V6 and has approximately 150,000 miles on the odometer. I was given the maintenance records of the vehicle and noted that the last oil change for the car did not specify the viscosity of the oil used. All previous oil changes were done at a different service center and had the correct SAE 5w20 specified. I noticed that on cold start up the engine would have significant knocking and after the engine warmed up the knocking would go away. The engine had full oil and the oil was clean as it had been changed a few hundred miles ago.
After watching one of your videos about the importance of using the correct viscosity oil, I quickly replaced the oil and filter using synthetic SAE 5w20 and a new MoPar filter. For the past three days there has been no knocking on startup and I think the engine is actually running smoother. Is this all coincidence or does this make sense because the (possibly) lower viscosity oil's improved ability to flow to the top of the engine? I'm not even certain what viscosity oil was in the engine before I changed it to the synthetic oil. Would adding high quality synthetic oil (regardless of viscosity differences) improve the function of an engine to that extent?
Thanks,
BluzGtr
Yeah it is a Chrysler....for sure...but...its been well taken care of and most of those miles were interstate commuting. The oil was changed religiously and its had preventative maintenance all its life. It does have weak AC, but I think its probably been that way from the beginning. It shifts smoothly and has plenty of pick up. The engine even sounds nice up around 6K RPM (cleaned the cobwebs out after the synthetic oil). That's why I think the knocking on startup seems strange. It has disappeared and I hope it stays gone for many miles.
Parts for these cars are inexpensive and there is plenty of room all around that little V6.
In the past people put a heavier viscosity oil in worn out engines. They may have put a heavier oil in there hoping it would stop making noise, but you would never want to do that in any modern car. Being an '07, I'm fairly certain that engine has variable valve timing, and it is designed for one specific viscosity. If you say the knocking goes away after using the correct viscosity, hope that no permanent damage or abnormal wear occurred. At that mileage, however, who knows how much longer it will go. It is a chrylser after all.
