How does time effect engine oil?

I’m a new Porsche owner and I just read an old thread discussing oil analysis which was interesting but it left me wondering why do most oil change recommendations include a time element. What does time have to do with degradation of oil?

It has more to do with moisture absorption, just like brake fluid. Most manufacturers recommend 2 years on brake fluid for this exact reason. Oil also absorbs moisture just sitting in your garage. Yearly oil changes are the usual recommended intervals. Sent from my SM-N960U using Tapatalk

Oil also degrades due to oxidation. The higher the temperature, the faster it degrades. The oxidation rate doubles for each 10 deg C increase in temperature. I change the oil much more frequently in my track car since it routinely operates at 250 degrees or more, even though it sees relatively few miles. Moisture is also a factor, which is why I always try to bring my oil temperature up well above boiling whenever I start the car.

Good to know. Concerning moisture accumulation I’m wondering how much affect boiling off has. Also if one does not run at 250 degrees ever and does not track their car is oxidation something to even consider with Mobil 1 oil ? Note that it keeps me awake at night. 😀 btw this site is great. I’m learning tons of useful information.

Oxidation occurs even at room temp, it just does it faster as temp rises. Most manufacturers seem to have settled on 12 months as the longest interval, regardless of mileage, even if they are paying for the service. Synthetic is standard fill on many cars now, and they retain that interval. I figure I can afford to change oil once a year, especially if DIY.

I'm sure I'm going to get flak for this, but I'm going to say that time doesn't matter (within reason). I recall that Blackstone Labs did a test in the past with old oils that were sitting open on a shelf. (I found tests with closed containers, but I can't find the one with open ones at the moment.) They tested those oils and found that none had "degraded" just sitting on a shelf. The TBN was good, there was no acidity, and the oils were fine... and this was after YEARS of sitting around. That being said, I also did a test with my friend's car... because I always hear people say to "store" the car with fresh oil at the end of the season, etc. His car was an old Chevy something (70's era, I forget exactly) and it was sitting outside in northeast MA in the snow, etc. The oil was driven for the summer, and he didn't have time to change oil before it was "stored" but it sat outside all winter long, which is when supposedly the warm/cold temperature swings would cause problems for an oil. I then paid to have it tested in the spring. The result was that there was no issue with the oil... it didn't care. As for the moisture in the oil... while it may pick up a bit more, it boils off the first time you run the car up again... so I'm not sure it's any more of an issue than a cold-start of an engine is to begin with. For these reasons, I believe time doesn't matter. But, that being said, feel free to do what you want. I have done a LOT of UOA testing with all of my cars, and never seen a time-related problem on any of the oils I have used. And, again, Blackstone proved this as well over longer time durations and with old-technology oils as well (eg dino oils from the past). But, that's my 2c... I'm happy to elaborate and discuss further if people have questions or concerns with my data... EDIT: I found some info at the following page: Newsletters | Blackstone Laboratories If you look at the Gas/Diesel section, you can see many of the older newsletters they have sent. "The Renuzit Experiment" newsletter has some info on an old oil that was leaking and such, but he put it in his truck and ran it anyway. Net result, no big deal... it was fine. The second is the series of "Ebay oils" where they tested many old oils (virgin samples, not used) to see what happened. The key is his text in the first one where he says "And, does oil go bad? We get this last question all the time, and my answer has always been no, but I was dealing with oils from the 1930s,1940s, and 1950s here--really old stuff." In the end, it doesn't seem his conclusion has changed even with these ancient oils.

I don't like Mobil one as much as Motul , I also hear liqui moly is good stuff. Having said that I run Mobil one because Walmart sells the EU formula at a great price (or they used to anyhow) and my mileage is so low at change M1 is more than good.

Separating the wheat from the chaff can be maddening. But fun to research and debate.

Maybe flak is too strong, but let me get it off and running. Glad you were prepared for this. : ) Oil in a container, whether open or not has little to do than answer the question about degrading in a car. Oil is not as bad as brake fluid at collecting moisture just in a can or bottle. Once you run the oil in an engine, you begin to break it down and introduce other contaminants like gasoline and the entire engine is a large void that fills up with ambient moisture that condenses at night and drops to the lowest point...the oil pan or sump. So the poster is correct, that running the car for an extended period of time, not necessarily track, just a long time, will evaporate moisture however the other contaminants that have been introduced by running in the car react differently to moisture and temperature changes so over time you have a chemistry experiment in your sump that should be changed. One year is what I go with as a guideline but there is room either way. The poster has a 987 which is not direct injection(let me know if wrong here) and is "normal" on oil degradation in normal situations. Direct injection motors like the 718 are harder on oil because of the higher temperatures and direct injection increases the likelihood of mixing fuel with oil when the injector is in the combustion chamber. If you use a long life oil, the manufacturer like BMW says you can go 2 years, but I can tell from my 718, it lives at 4000 rpm all the time whereas my BMWs are closer to 3000-3200 and the redline is over 7000 rpm. So depending on what you do, you can go 1 - 2 years if you take periodic long drives to burn off moisture but there are all sorts of chemicals that accumulate and react in the oil, that can then react with your oiling surfaces. So fresh oil is good. As to shelf life in a bottle, that is probably a long time for engine oil and I defer to your article on shelf life in the bottle. Also, dealers are not experts on oils, so beware. They are mechanics not engineers. My BMW 1M had a 45000 mile transmission and diff oil change only be be told countless times by dealers that despite the owners manual, it was "lifetime" fill. After getting fed up with having to deal with ignorant people working on my prized car, I purchased a couple of bottles of LT-5 transmisison fluid to do it yourself. The bottles came with an expiration date 5 years from manufacture..in German. That was just sitting in the bottle, not even in the car...but transmisison fluid is different than motor oil, but the point is, even the dealrers don't know that much.

987.2 / 3.4 six is direct injected the 2.9 is not.

Thank you. Good to know!! Yes, and I hope that came across in my reply that I concur that shelf life is fairly long for oil if kept in good conditions. I also see now that the OP question is too generic. I immediately assumed he meant in the car whereas I can see now that he just asks about time which means both conditions. So I think we both stated good points on both conditions and I apologize for mentally adding "in the car" when it's not in the original question. So OP, in the bottle as Schwinn mentioned, it can last a long time if stored in a cool place. Once in the car there is a lot more interior volume for condensation. Additionally once the oil has circulated through the engine, the detergents in the oil begin a chemical change as they deal with metal content, moisture and gasoline being introduced. This will break down oil over time which is why synthetic oils are now the norm as they can resist gasoline break-down more than conventional oils. There are a lot of variables (engine operating rev range, ambient temperatures, turbo charging, direct injection, age and operating condition, driving style..normal, aggressive, driving trip duration....short trips, long trips) that come into play with oil which is why you can have a range of 1-2 years to change it from manufacturers, but it is a consumable product and should be changed even if just sitting in the car. I hope this helps and sorry for the confusion on the OP question.

What about additives in the oil? I change my oil yearly for the additive degradation as much as anything. Also I watched a YouTube by an engineer on Direct injection engines and he says fuel gets in the oil and short trips don’t heat the oil up enough to evaporate the fuel. Since watching this I try to take my car on a drive long enough to get the oil over 200 degrees every week or so as I take a lot of short hops around town- my Boxster gets twice the mileage of my Tundra. Also my Indy mechanic recommends Liqui-Moly full synthetic over Mobile1 for the additives as much as anything. Thoughts/opinions?

Mobil 1 is full synthetic too and if you are using the variant recommended for your car both are fine but it's not just about brand. You could have oil made out of Unicorn Urine brand but not certified for your but if he means between a certified Móbil 1 and Lubro moly. That's fine. Both are good but what matters more is using the explicit variant recommended for your car. It is exactly this issue with direct injection that makes the composition more critical. The certified oils are tested to last a longer duration without breaking down so if you use lubro moly Make sure it has the right weight and certifications for your specific car. You have to be careful about past experiences. I hear all sorts of stupid things from people like "I ran my oil for 2 years intervals and 20k mile changes on my 1996 330i and it lasted 300k miles!" That was a normally aspirated, port injection car with 6300 rpm redline. That means squat when talking about a turbocharged direct injection 4 cylinder with a 7200 rpm redline mounted midship not in front. So just because someone including a mechanic had great past experience with something it is not necessarily comparable so just be aware of that.