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Old 11-21-2014, 05:07 PM
 
Location: Eastern Washington
13,388 posts, read 42,713,043 times
Reputation: 11470

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Quote:
Originally Posted by ansky View Post
I use synthetic oil and I only drive my car about 3k-5k miles per year. It has now been a year since my last oil change as I've only driven about 3k miles and I know with synthetic you can drive up to 10k miles before needing an oil change. Does it matter that the same oil has been in my car for a year? Does synthetic oil "expire"?
Guys,

The OP did not state how he accumulates the 3 to 5K miles per year. I see a lot of you are assuming short trips, but that's not necessarily so.

OP, post up and say how the car is used - what's your typical trip length?

Then the assembled bretheren can give you good advice.
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Old 11-21-2014, 07:36 PM
 
770 posts, read 563,784 times
Reputation: 1475
Quote:
Originally Posted by Blondebaerde View Post
On the unlikely case it actually matters in the details, obtain an Amsoil or similar oil-analysis kit and run your own experiments to find out the best answer for your particular use-case. That is the only answer that even remotely makes sense, moving from the realm of "opinion" to "facts." Given the kits are roughly $35 postage-paid, I assume odds of most people actually doing this are pretty low. Just saying, though.

Exception to the rule: we tested oil on race bikes (motorcycles) in the 1990s, as in "a lot." Knowing when an engine or transmission was about to dynamite itself actually mattered, given we were pushing machinery right to the edge and sometimes beyond. The testing was part of our budget.

In contrast, it seldom matters in that level of detail for passenger cars. I've a few run oil analysis kits on my 911 Turbo out of curiosity, and not very often, to see if expensive parts were slowly self-destructing (did not appear to be). Otherwise, I'm sticking to a certain interval approved by people who actually know what they are talking about (speed shop who race 911s in Seattle metro). The mileage interval is both irrelevant for others and specific to my use scenario, as is both the type and weight of (full-synth) oil.
Sounds like you know what your talking about and have much more experience than most here.

So I am curious, how often do you change your oil on the 911? Or what circumstances dictate when you change it ?
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Old 11-24-2014, 11:52 AM
 
Location: Kirkland, WA (Metro Seattle)
3,422 posts, read 2,816,376 times
Reputation: 5879
This is a minefield subject, full of opinions and speculation vs. facts. The only way I personally know of to resolve it is case-by-case, based on your usage scenarios and oil analysis.

Very few of us go through that bother, thus we follow the suggested maintenance intervals from the manufacturer and/or whatever makes us feel good based on opinions. I say: great.

I trust few people who have something to gain by "suggesting" I do *anything*. The oil places, and dealers, and any repair shop, is money ahead if they suggest a change interval less than is truly necessary. I don't *think* the manufacturer, in contrast, has much to gain by doing-same...but they are also trying to cover their own behinds to ensure oil failure doesn't explode the engine.

So: to answer your question, I have to some degree delegated the decision on when to change oil, knowing the risk of doing so. Make sense? I think the vast majority of us have to do that, on an interval that we feel (what I call) "emotionally comfortable" with.

I have therefore indicated, implicitly: "The speed shop in Seattle metro, guys who race Porsche 911s, have torn down more engines than all my friends and me duct-taped together. They've been around many years. In-general, they have demonstrably sound council on various parts and service for 911s, based on word-of-mouth from others and my personal experience. Yes, they stand to gain if I change oil more often than is necessary. OK, I can deal with that. But they are also willing to walk me through the what, and why, for my particular model. I am an educated layman, and can speak competently on their terms, thus I cannot easily be bamboozled. They know that."

My experience, then: 1) Porsche 911 Turbos are demonstrably "demanding" on oil, but it does depend on how hard you push the car and other environmental circumstances. 2) given that, there are several kinds of full synth oil both recommended and encouraged by other users (real drivers), with demonstrably positive wear characteristics over time.

In the end, for my specific driving style, annual mileage, etc. I go about 8K-9K miles between changes, and use one of two specific synth oils AND specific weights. That is, btw, bi-annually in my case. My car "likes" ...i.e. leaks a bit less from the turbo seals...Motul 8100 X-cess 5W40 vs. my other favorites, Castrol Syntec 0W-40 OR Mobil 1 0W-40.

My 911 is driven only several times per week, 52 weeks/year, in mild to nasty conditions (Seattle area: can be dry, or pouring rain, or even on-occasion below freezing and snowy). The AWD is awesome when below-freezing and in light snow. They sand, but do not salt (TTBOMK), these roads. The grit and grime level definitely goes up for about half the year, though.

YMMV. Hope that helps, vs. confound further.
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Old 11-24-2014, 11:55 AM
 
Location: FLG/PHX/MKE
7,289 posts, read 12,868,909 times
Reputation: 11529
Quote:
Originally Posted by ansky View Post
I use synthetic oil and I only drive my car about 3k-5k miles per year. It has now been a year since my last oil change as I've only driven about 3k miles and I know with synthetic you can drive up to 10k miles before needing an oil change. Does it matter that the same oil has been in my car for a year? Does synthetic oil "expire"?
I'm in the same situation with a couple of my cars. I get the oil changed once a year and use synthetic.
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