rwiii

I understand our oil has cooling powers, lubricates the engine and pushes foreign materials to the filter. Oil does not "break down" for tens of thousands of miles regardless of summer vs. winter operating temperatures. Does it go stale like milk? What difference does it make if it exceeds one year old?
I run more than 10k miles a year so this is really not relevant to me. I'm sticking with the 5k mile changes to represent to a future seller that I perform frequent maintenance; but, in realtity shouldn't oil be changed because it gets dirty and not because it goes bad or breaks down?

Dennis C

I believe that moisture in the oil is the enemy, which can corrode internal engine components.

Flat6 Innovations

Corrosive wear and high total acid numbers in oil are often not considered. Time and experience has taught us that a 6 month/ 5K mile service interval is what these engines like. If you listen to the engine you'll never go wrong, because it doesn't know how to lie.

TSMacNeil

I'm not a "Porsche- Whisperer", but I'd guess the special additives blended in the oil would have a suspension issue if left "un-stirred" via use. Motor oil is only a few processing steps beyond that of diesel fuel.
Diesel fuel becomes extraordinarily unstable if left static for any extended period of time. Moisture, algae, and general funk of de-homogenizing ruin the fuel and wreck the fuel tanks of diesel systems. Ask any diesel boat guy how old fuel affects their boat...

I'd guess some similar badness happens with stale oil over time.

dgjks6

But wouldn't they then degrade on the store shelves?

LexVan

Not in a sealed HDPE/PET bottle, and the rate at which it is sold in high volume retail stores.

STAGGERWING

Some very good comments in this thread . From years of flying with & rebuilding Rotax motors , it is commonly accepted & been documented that synthetic lubricants are moisture producers when left for any period of time in a dormant motor . Yes, I'm referring to 2 stroke motors , but this has also been documented relative to 4 stroke as well . With the current use of synthetic oil being used today in everything, I have to believe this moisture problem has somehow been curbed by the oil chemists but to what extent , who knows ?
In my 01 C4 manual it mentions using a syn blend (syn & natural oil) as an acceptable oil , which I may do rather than a full syn, or maybe straight non syn as offered by Castrol , my oil of choice for many yrs except for Rotax 2 strokes , whereby a natural oil based mix is used by most everyone for best lubricity , worry free storage , & low carbon buildup .
So, should you chg your syn oil after an extended dormant period--definitely, as verified by the excellent comments mentioned by Jake , Dennis , & TS Mc Neil .
I run non syn in my street rods & do not worry about moisture, storage, or lubricity ---if the oil stays clean--I drive it , up to 3-4 k , then chg .

Bob

01 C4

31 Ford cp chp & ch, 302/350

40 ******, 302/350, IFS

38 Ford cp, 327/350, IFS

57 Belair

62 356B --long ago

Brighton 911

If you are doing an annual oil change and storing the car for the winter 4-6 months, do you change the oil before you put it away or as soon as you put it back in service? Coming over from Corvettes and we always changed the oil in the fall before storage, assuming the same with the 996.

wyovino

Just to confirm: Oil changes should be done twice a year at a minimum regardless of the mileage. Correct? I've been changing the oil every 5k miles which is usually just once a year.

alpine003

You feel like rebuilding my Rotax out of my Aprilia RSV1000? I think it has a couple bent valves.

Longtail996

alpine003, how in the world? When I twist up my Aprilia it goes so damn fast, I gotta back out of it!

DBJoe996

It doesn't matter the make/model of car...oil is oil and it wears out. Change it twice a year, spring before it gets hot and fall before the dregs of winter hit, if it's a daily driver. It is such a small price to pay when you're gambling with a very expensive motor. Use a Porsche recommended total synthetic oil. I run M1. Been doing this for 50 years on every car I've owned. It just feels right to have fresh oil in the car, and doing an oil change just makes you feel good. 99 C2 996/911 DD w/130,000 miles. As the commercial goes...just DO IT!

Macster

Change the oil/filter before putting the car away for the season.

This removes the old oil with its acids and the engine spends its idle time with the least corrosive oil in it.

Macster

Synthetic oil doesn't wear out. What happens is it gets contaminated with mainly water and other combustion byproducts.

Water lowers the oil's viscosity to the point its ability to provide high temperature high stress oil film protection can be compromised.

Additionally the water and other contaminates combine form acids, and these attack everything the oil comes in contact with.

Draining the oil removes all the water and acids and the fresh oil brings with it a full strength additive package and the process starts all over again.

halik

Err who told you that nonsense to begin with? The air inside the crank case is a sealed system, so whether you run it 5K miles in 1 year or two years won't make any diff vis a vis air moisture etc.