I get what you say, but that's a tad broad and simplistic. 3000 miles in 4 months, yeah makes no sense but what if you drive 1500 miles per year on Sundays only. That's a two year interval...there is science for changing it then. I totally get your point but we just can't forget the intervals are a combination of miles, time and operating conditions.
Cayman S oil change
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I disagree with the time component of the equation. I have done UOAs (as have others) and they have all shown that oil doesn't "age" just because it's sitting in the vehicle. In my own testing, the additive package remains fine over time, and the theories about engines developing condensation inside the motor are also unfounded (at least to any level that affects the oil).
Personally, I haven't seen a reason to do change based on time, and so I won't bother to do that. I'll stick to mileage and will continue to do UOAs to confirm this, as I have always done. Then again, I generally drive my cars more than not, so I don't get long sitting times anymore...
That being said, people can certainly change it more often if they want to... it certainly won't hurt anything other than your wallet (and maybe the environment).
Personally, I haven't seen a reason to do change based on time, and so I won't bother to do that. I'll stick to mileage and will continue to do UOAs to confirm this, as I have always done. Then again, I generally drive my cars more than not, so I don't get long sitting times anymore...
That being said, people can certainly change it more often if they want to... it certainly won't hurt anything other than your wallet (and maybe the environment).
Noted. Here is a quick piece from Amsoil, not from me: Why Motor Oil Deteriorates – AMSOIL Blog
Oil in a bottle deteriorates over time depending on how stored but it can take a long time. Once you run the oil in your engine it is contaminated an no longer contained in a plastic semi-inert container. It is now sitting in your engine exposed to metals, condensation and exposed to high heat with metals. In the case of direct injection engines like the turbo motors, it will also have some fuel that will mix with the oil causing different chemical processes over time. Non direct injection cars on average mix less fuel with oil because the spray doesn't happen in the combustion chamber like DI motors. So that soup sits in your engine and the longer it does, the less efficient it will be at doing it's job. Again it depends on the type of engine, humidity and a host of factors which is why the manufacturers all recommend a time component.
I don't disagree with what Amsoil is saying... but remember, they're comparing themselves to conventional oils. I certainly haven't used a conventional "dino" oil in ages... I have been using synth oils since the 90s on my "normal" cars back then, and certainly on my modified Subaru turbo. Even on the turbo, which was the hardest on oil (for obvious reasons) it would last almost 10k if I wanted it to, with no real correlation to time.
What's more, many of the things they mention are caused by a running engine... not "sitting around time" (high heat, contamination, etc). Yes, contamination would "sit around" in the oil, but in a modern oil it won't continue to "damage" the oil just because it's sitting there. At least not for normal time scales (year or so).
Even still, Blackstone did some tests with some old "Ebay oils" to see how they held up after decades of sitting around. In addition, they even ran one in their test vehicle, to see what would happen. Now those were truly the old "conventional" oils, and some didn't even have additives... but they were fine as well. (See Newsletters | Blackstone Laboratories - the newsletters about the "ebay oils" and then the test with the "Renuzit experiment").
Would I run an ancient oil in my cars today? Not unless I had to... but the point is that modern synthetics with additive packages will last far longer, and that means longer than a year or two (since these ancient ones are decades old). Again, it doesn't hurt to change it more often if you really want to... knock yourself out. I wouldn't bother, myself, that's all I'm saying.
What's more, many of the things they mention are caused by a running engine... not "sitting around time" (high heat, contamination, etc). Yes, contamination would "sit around" in the oil, but in a modern oil it won't continue to "damage" the oil just because it's sitting there. At least not for normal time scales (year or so).
Even still, Blackstone did some tests with some old "Ebay oils" to see how they held up after decades of sitting around. In addition, they even ran one in their test vehicle, to see what would happen. Now those were truly the old "conventional" oils, and some didn't even have additives... but they were fine as well. (See Newsletters | Blackstone Laboratories - the newsletters about the "ebay oils" and then the test with the "Renuzit experiment").
Would I run an ancient oil in my cars today? Not unless I had to... but the point is that modern synthetics with additive packages will last far longer, and that means longer than a year or two (since these ancient ones are decades old). Again, it doesn't hurt to change it more often if you really want to... knock yourself out. I wouldn't bother, myself, that's all I'm saying.
I agree. Modern synthetic oil is pretty amazing stuff. On my old street/track E36, I kept doing oil analysis and worked my way up to 10k intervals with about 10 track days and a couple autocrosses per change. Still good to go. And that's an old tech motor. I run 5kish on the Cayman with 6-8 track days and for two changes so far and the tests are still good.
I once heard from Amsoil that good oil can go for 30k+, its more the filter that gets filled up, so if you change filters, you can actually change the oil less frequently. Actually, now that I think about it, I did filter changes at 5k with the E36 while doing the oil at the 10k mentioned above. The filter is right on top so its very easy to change.
I once heard from Amsoil that good oil can go for 30k+, its more the filter that gets filled up, so if you change filters, you can actually change the oil less frequently. Actually, now that I think about it, I did filter changes at 5k with the E36 while doing the oil at the 10k mentioned above. The filter is right on top so its very easy to change.
Just ran across this post by @ledbette about a study done on fresh oil versus used oil: Oil temps at the track on stock 981S (with 3.4L)
Basically, the SAE tested "old" oil versus "fresh" oil and how it wears on camshafts. Longer story short, the testing shows that new oil is not better than old oil, thereby implying that changing it too often is not actually productive.
Don't get me wrong, this doesn't mean that there aren't other factors to be aware of (viscosity changes, filtration capacity, etc) but the point is that you can technically change oil too often and get measurably increased wear. I say "technically" and "measurably" because as the paper notes, even though there is higher wear on the fresh oil, "its absolute value is still quite low and quite acceptable." So, we're talking about small amounts, but the point is that wear is still lower for "old" oil, and therefore technically better. In fact, the test put old oil onto a used shim, and found lower wear and then put the new oil back on the used shim and saw it go high again... proving that the old oil is the factor here, because it has changed chemically in some way. Very interesting...
My takeaway is that you don't need to change oil based on time (as I mentioned before)... and that changing it with less miles on it is likely not "better" than leaving it there. Again, these are small amounts of change, so you can certainly change it every year or whatever if you really want to, but I see no point in that, and will continue to ignore time on my vehicles (as I always have).
Basically, the SAE tested "old" oil versus "fresh" oil and how it wears on camshafts. Longer story short, the testing shows that new oil is not better than old oil, thereby implying that changing it too often is not actually productive.
Don't get me wrong, this doesn't mean that there aren't other factors to be aware of (viscosity changes, filtration capacity, etc) but the point is that you can technically change oil too often and get measurably increased wear. I say "technically" and "measurably" because as the paper notes, even though there is higher wear on the fresh oil, "its absolute value is still quite low and quite acceptable." So, we're talking about small amounts, but the point is that wear is still lower for "old" oil, and therefore technically better. In fact, the test put old oil onto a used shim, and found lower wear and then put the new oil back on the used shim and saw it go high again... proving that the old oil is the factor here, because it has changed chemically in some way. Very interesting...
My takeaway is that you don't need to change oil based on time (as I mentioned before)... and that changing it with less miles on it is likely not "better" than leaving it there. Again, these are small amounts of change, so you can certainly change it every year or whatever if you really want to, but I see no point in that, and will continue to ignore time on my vehicles (as I always have).
One more reference to provide. This is a podcast by Blackstone (one company that offers UOA testing) and in this episode they talk about old oil:
Feel free to listen to the whole episode, but at the time I have in the link (3:47), he goes into the question of whether an oil that's been sitting in a car needs to be changed. Again, he says "calendar time, alone, is not going to cause oil to break down even once it's in the crankcase". Yes, this is with regard to modern (non-open-breather or basically anything since the 90s) cars only... but just another reference I came across.
Also, he mentions that they have a Porsche specific podcast in the next episode, if anyone is interested:
The video version of this can be seen here:
He repeats that you don't need to worry about calendar time on this podcast as well (12:47 of the second link)...
OT: Incidentally - is there a way to post YT links without having the board convert them into giant images? I changed them to CODE, for that reason, because I found it annoying...
Code:
https://www.youtube.com/watch?v=n-2lhi7S5ms&t=227sAlso, he mentions that they have a Porsche specific podcast in the next episode, if anyone is interested:
Code:
https://www.youtube.com/watch?v=O3AuljDVX3E
Code:
https://www.youtube.com/watch?v=_6s84E8Mx-kOT: Incidentally - is there a way to post YT links without having the board convert them into giant images? I changed them to CODE, for that reason, because I found it annoying...
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For forty years I have annually changed the engine oil in all of my cars regardless of running time, miles, climate, or type of driving. ‘Always in the Spring of a four-season climate including no running over the harsh Winter months. I’ve never had engine trouble with any of them. The older ones (Porsche, MG, Jaguar) use traditional mineral oils and the new cars (Porsche, Mercedes- Benz) get synthetic per factory fills. I budget this as a routine operating cost. Choosing the correct oil type and weight is important for your engine type, usage, and ambient climate conditions. Keeping an eye on engine oil levels is important as well. The British cars offered two methods to watch oil levels: on a dip stick or on the floor under the engine! Air cooled 911 Porsche engine oil fills can be as high as 14 quarts with auxiliary oil coolers and long feed/return oil lines. This makes 100% oil evacuation nearly impossible. An annual oil change helps settle that issue for me as well. Transmission lube and brake fluid are just as important and also require a renewal regimen. This approach has provided excellent performance and peace of mind.
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Those weren't setup as links, but rather CODE because I didn't like the giant Youtube MEDIA processing the forum did (it made it hard to read the text in-between). That being said, the links are there but inactive, so you can copy the text and paste it as needed.
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