Why would Jiffy Lube put 10w 30 in A engine that says to use 5w 30?
There could be a number of reasons they used a heavier weight oil, or it could have just been plain negligence. For starters, no the 10W will not harm your engine. I actually recommend a heavier weight to many of my customers with high mileage. As time goes on and the miles rack up the “space” oil needs to fill between bearings, etc becomes larger. A heavier weight oil helps to reduce unnecessary friction in this situation. The high mileage oil was a good choice, it’s not a gift from the car gods but it does have some benefits over traditional oil for cars that are getting up there in age. I’m not so sure what the point of synthetic was, I’d switch to a 10W-30 high mileage conventional. In most cases putting synthetic oil in a car that’s run conventional for 15 years is not a great idea. I usually advise my customers if they want to run synthetic (a better option from the get) to start when the car is new. I would not be concerned about your current situation. The heavier weight oil wa
