Originally Posted by Goldwing
Yes, I'm a little cheap, but also I don't want to throw out perfectly good oil (think green). I changed the oil (Mobil1 0W-40) last fall and drove the car less than 1000 miles this summer. Not raced, not dusty conditions, just gently around town and some highway. The oil on the dipstick still looks golden, not dirty. Given I'm using a top-rated synthetic, is it really mechanically necessary to change the oil? (Please don't tell me it's cheap "insurance"...I really want to know if synthetic oil breaks down with age or is good for a couple years.)
The engine oil is good for two years in your oil pan.
The biggest things to worry about are water condensation building up, and gas dilution.
So lets look at these two items separately.
Fuel dilution of the engine oil:
It occurs when the engine is started up cold, when the computer adds more fuel to mixture to get the engine to warm up quicker, and idle better when cold. If you take one poster's advice and just start the car up every once in a while, you are guaranteed to increase the amount of fuel in the oil, and that's the worst possible thing that you can do to the engine oil. You are better off just letting the car sit for long periods of time than to occasionally run the engine cold.
Water condensation:
Water is in the air as humidity all the time.
There is more in the air in Florida than there is in Arizona.
That said, your engine is a fairly air tight contraption, due to emissions regulations.
They don't want the oil vapor getting out of the engine into the atmosphere, so the engine is built with an air tight PCV system. So basically, unless you leave the car parked with the oil cap off, or unless you altered the hoses on the engine in a bad way, you shouldn't get very much condensation in the engine oil from normal circumstances.
The great thing about water is that it boils at a much lower temperature than engine oil does. So the easiest way to get rid of it from the oil is to simply drive the car until the oil is good and hot. When the water boils, it gets sucked into the PCV system, and the engine burns it with the fuel, and you no longer have water in your oil.
A simple 50-100 mile drive on the highway should eliminate all of the water in the oil, unless you poured in a gallon of it.
Gasoline is a little harder to boil out of the oil, simply from the fact that you would have to get the oil considerably hotter. You would actually be better off draining the oil out of the engine, putting it into a large lobster pot, and using a liquids thermometer, bring the oil up to about 300 degrees, and keeping it there for about 30 minutes.
You could actually do the same for water dilution, but then you would only need to bring it up to about 225 degrees.
So no, you don't need to change your oil because its a year old with only 1k miles on it.
If you can take the car out for a good long drive, that will suffice.
BC.