Quote:
Originally Posted by Resist
With all my vehicles over the years I have followed the manufactures mileage numbers for oil changes. I've never believed in the 3000 mile oil change theory. Those days are long gone. As far as the time portion goes, it is funny how time doesn't start for new cars sitting on a Dealerships lot until after it is sold. So I only use time if the vehicle sits for long periods, like when stored.
|
The reason the amount of time that a car sits on the lot (as a truely "new" car) is because the problem with oil isn't just the oil breaking down or getting dirty, but also the acids and moistures that naturally get into the oil as a side effect of combustion.
Once acids and moisture get into the oil, then it will start to harm the inside of the engine even if the car is sitting unused.
Since a "new" car has had almost no combustion, it's oil is relatively pristine. Those cars can sit on a lot for a very long time. Once several thousand miles have been put on the oil, the oil will have acids. That oil can be harming the engine and should be removed. Synthetic oils can be a false sense of security because they "look" good even after a lot of miles, but that doesn't change the fact that combustion is still introducing acid & moisture into the oil.
That's why they tell you to change your oil every 6 months OR x-thousand miles and not just the miles alone.
If you do want to store a car for long periods, then it's best to change the oil *just* before putting it into storage.