Do you really EVER have to change synthetic oil?

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Originally Posted By: MolaKule
But the physio-chemical facts are that in an ICE, and when subjected to heat and oxidation and contaminants, the oil does degrade, and thus must be changed. How often the oil must be changed depends greatly on the how well the specific oil and engine play together.

When you really think about it, the oil's exposure to blow-by gases, fuel dilution, oxidation, moisture, mechanical stress, and thermal cycles, in some combination unique to any particular engine, causes chemical degradation.

As drivers, we can only guess at what's going on. Most modern cars use an Oil Life Monitor OLM which keeps track of oil chemical degradation based on how stressful the scenario is. I mention OLMs since this is the only way to carefully engineer in longer oil drain intervals. I wish there was a way to tell the computer what kind of oil you're running so it could extend the interval for you, yet they usually just design the OLM algorithms for the least spec oil allowed.
 
Originally Posted By: tig1
Originally Posted By: AZjeff
Originally Posted By: car51
Member TIG1 uses Mobil 1 0w20 and goes 10,000 oci


What's special about that? Our RAV4 specifies 0W20 and that OCI. You mean 100,000 maybe?


What's special about what I do for OCIs is that I have been doing 10K OCIs for 37 years with M1. Others have done that, but not many.


Apologies then. Did not know you're one of the visionaries of BITOG!
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Originally Posted By: oil_dude08
Hi guys, I had a quick question. If synthetic oil is designed to NOT breakdown, in theory, can't we only just change the oil filter and let the filter clean out this oil instead of swapping it?


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I found your oil. Here's the oil you need
grin.gif


http://www.synlube.com
 
Originally Posted By: Pontual
Originally Posted By: HTSS_TR
This is what would look like if you don't change your oil, synthetic or dino.

A BMW engine with too long OCI, even with synthetic oil.

2010-03-13_223016_bmw_sludge.jpg


Nobody knows theaverage oci these engines had gotten... 15k once 20k twice, a few 30k after all that? Assuming synthetic in this case.


A friend that lives in Florida worked as a mechanic at the local BMC shop and saw many BMWs sludged to one degree or another. He said every one of those engines used dino and extended the OCI too long. He now has his own shop and recommends synthetic for many of his customers.
 
Just to see what would happen, I ran my last car out to slightly over 15,000 miles (24,000 km) using a full synthetic I'd thrown together in the lab.

As I recall, the oil seemed to be doing just fine; wear metals very low, some TBN depletion but nothing to worry about and some fuel dilution.

What there was to worry about was that 40% of the oil had disappeared from the sump! And that for me is the flaw in long-term use of synthetics, because if you have a engine that uses oil, synthetics burn just as readily as minerals and create exactly the same problems of chamber deposits and stuck oil rings.
 
Originally Posted By: aquariuscsm
Originally Posted By: oil_dude08
Hi guys, I had a quick question. If synthetic oil is designed to NOT breakdown, in theory, can't we only just change the oil filter and let the filter clean out this oil instead of swapping it?


grin.gif
I found your oil. Here's the oil you need
grin.gif


http://www.synlube.com


In all seriousness, has anyone on the site looked into this? Interesting in the least.
 
A person that buys such specialized oil, would never let it installed for life. Just short of 10k miles
 
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Originally Posted By: oil_dude08
Hi guys, I had a quick question. If synthetic oil is designed to NOT breakdown, in theory, can't we only just change the oil filter and let the filter clean out this oil instead of swapping it?


ALL oils break down, in fact most fully synthetic oils on the USA market are simply oil with an extra refining step.
The only reason you think synthetic is designed to not break down is because of oil company marketing. Yes it is reasonable to expect synthetics to resist break down longer as the extra refining step should make the oil a bit more stable but if you listen to whatever is in your owners manual you will be good to go no matter syn or conventional.

Conventional and Synthetic oils carry the same API rating. Meaning, they both meet the same standards for the very same tests and will both last as long as necessary between oil changes required in your owners manual. They will both produce wear numbers, shear numbers and "breakdown" numbers meeting and exceeding the certifications on the bottle.

Lets say, an oil was capable of lasting forever, it would be impossible to keep forever, ALL engines wear and leave all kinds of nasty metals and combustion leaves nasty acids in the oil, sooner or later you need to change out the oil to get rid of that nasty metal and acids.
A filter will only get the large pieces of metal the ones that do harm to the engine. The fine pieces over time will still tend to polish and wear.
 
Originally Posted By: Bassnjunky
All oil oxidizes. Synthetic just takes a little longer than mineral oil to oxidize....


Well said, in a lot less words then I did!
 
alarmguy, ^^^^ good summary, except what do you mean "Conventional and Synthetic oils carry the same API rating...both meet the same standards"??? Wrong there. Synthetics will have higher standards they meet, like dexos1, 4718M, LL-01, A40, 229.5, HTO-06, A1/B1, etc., I've even skipped a few more here.
 
Originally Posted By: rsylvstr
Originally Posted By: aquariuscsm
Originally Posted By: oil_dude08
Hi guys, I had a quick question. If synthetic oil is designed to NOT breakdown, in theory, can't we only just change the oil filter and let the filter clean out this oil instead of swapping it?


grin.gif
I found your oil. Here's the oil you need
grin.gif


http://www.synlube.com


In all seriousness, has anyone on the site looked into this? Interesting in the least.


There is an internet website for anyone and everyone who wants to spend money.
This company has been around for 50 years. There is no holy grail to changing oil and this company wants to sell you $30.00 an almost quart of oil.

Look at it this way, in the last 50 years, if this company was credible. Dont you think one automaker out of the WHOLE WORLD would be filling their engines with this stuff and advertising never change you oil? (after the first service)

Ill sell you an oil that will last for life too. Lets see, 4.5 quarts, that will be $156.00 please! oops! Lets not forget the special oil filter too!
 
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Originally Posted By: lubricatosaurus
alarmguy, ^^^^ good summary, except what do you mean "Conventional and Synthetic oils carry the same API rating...both meet the same standards"??? Wrong there. Synthetics will have higher standards they meet, like dexos1, 4718M, LL-01, A40, 229.5, HTO-06, A1/B1, etc., I've even skipped a few more here.


If you notice I said API ratings.
Up to the person to read their manual to know what rated oil they need.

It all depends on what your owners manual calls for, BTW, there are semi dexos oils out there.

Up to the person to read their manual to know what rated oil they need. Every time we discuss an oil we do not list all you mentioned above.
 
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This might have been posted already but oil companies usually recommend that you follow the car manufactures OCI.
 
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Closing in on 70,000km's (44k miles) since my last OC. Use the Canadian equivalent of 0W-30 Delvac-1 full synthetic HDEO. No issues whatsoever, and if you search, I posted pictures with the oil pan removed at approximately 60k km's where the condition revealed no sludge and minimal varnish buildup.

So to answer the OP's question, it is perfectly possible, with the right oil in the right engine. Many large industrial engines and fleets do not do oil changes at regular intervals, but rather, do so "on condition". If the engine design and oil quantity involved is sufficient, oil only suffers minimal oxidation.
 
Originally Posted By: alarmguy
Originally Posted By: Bassnjunky
All oil oxidizes. Synthetic just takes a little longer than mineral oil to oxidize....


Well said, in a lot less words then I did!


The oil also suspends combustion by-products. It can only take so much.

Originally Posted By: Pontual
Nobody knows theaverage oci these engines had gotten... 15k once 20k twice, a few 30k after all that? Assuming synthetic in this case.


I don't know about that particular engine. However, I've seen the same M54 engine sludged up the same way when it was posted online by a BMW dealer technician. He said someone drove 50k miles without an oil change. So it takes a long time to get to that state.
 
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