Quote:
Originally Posted by Blubaron79
Without starting a debate: synthetic oil has also gotten better, and so have engine tolerances. It was 15k before free maint. It did go back to 10k between changes.
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I agree 100%. I also wanted to avoid firing up the age old debate. I've used synthetics since Mobile 1 was first introduced. Engines are far less dirty than they used to be. With the advent of fuel injection and all of the mechanisms in place to reduce emissions there's far less blow by and raw fuel/contaminants fouling the oil.
But, mileage in and of itself isn't really even relevant to the discussion of the condition of oil. You could probably run a car 24/7 for years in ideal conditions without changing the oil or filter - assuming contaminants weren't introduced as noted above. The number one contributor to oil life expectancy is whether the oil is brought up to full operating temperature every time the engine is started. If it's not, then you'll have a build-up of sludge resulting from condensation in the oil. All of the horrific pictures you see floating around of plugged filters at 15k intervals are from cars in that class. Driven just a few short minutes at a time - every time they're driven. The worst thing you can do to any piece of machinery is start and stop it cold.
So, the operating cycle and frequency is far more relevant to the discussion than miles covered. I change every 5k purely because I'm too lazy to keep track of which car is due and when. I'm confident I could likely go 20k without any issues in MOST of them. The older cars probably wouldn't like that. In the grand scheme of things, the oil, filters, and time (I do my own maintenance and repairs) are FREE in comparison to the money invested in the vehicles.
I forgot to add - new cars are shipped with special break-in oil that has a higher percentage of mineral oil in the base stock as well as additional amounts of zinc and phosphates to aid in the break-in process. This oil actually has LESS lubricity and wear protection and typical synthetics. The main reason for a shorter than normal change cycle for the first change would be to get a higher level of protection once the motor is officially broken in. The M cars usually have a break-in interval listed because their engines are developed to use 10/10s of the available power. The non-M cars generally aren't operated in a similar fashion so they can get away with keeping it in there. If you are going to redline your poor car from every stop then you should change after the first couple of thousand miles...