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post #11 of 17 (permalink) Old 12-03-2005, 12:16 PM
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After 40 k "synthetic" miles, three used oil analyses by me and more from others, and a fair bit of reading I am still trying to understand the issue. The mpg improvement seems insignif but some people in cold climates see it. Still don't know the max. "reasonable" oil change interval because I have been scared to push it beyond about 13k. Mobil 1 synthetic starts to lose its ability to neutralize combustion acids about then. The preponderance of evidence (from other engines) is that synthetic leaves the internals squeaky-clean even after many years. OTOH, conventional oil can do the same, if one changes it often enough to preclude any thermal breakdown.

With synthetics the engine simply does not release any "wear metals"; a matter which has surprised the folks who do the analyses and presumably know about those things. We simply lack Prius data whether conventional oil every 5k does as well.

If changing Prius oil on a 5k interval, it can be argued that there is little or no synthetic advantage. Obviously one is "wasting" less oil on longer change intervals, but I am not trying to convince anyone to flirt with warranty issues.

DAS
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post #12 of 17 (permalink) Old 12-03-2005, 09:14 PM
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"One thing about synthetics is clear; they are not based on petroleum."
************************************************** ***
That's a question I've never seen explained. Just what is synthetic oil made from/of..? It feels like petro..it smells like petro..etc...
(I've used castor oil in 2 stroke race engines and olive oil in the kitchen.)

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Hey.. \"it's just a car...\"
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post #13 of 17 (permalink) Old 12-03-2005, 09:49 PM
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I have a few questions related to this thread. I'm going for the 10,000 service on Tues. I am wondering about whether to stay with conventional oil or switch to synthetic. My neighbor was an auto mechanic and says it might not be a good idea to switch since once you go with regular oil, that by switching to synthetics and then going 10,000 mi. without an oil change, there is still regular oil mixed in with it that won't last that long and therefore can be bad for the ICE...just his personal thought. Is this a valid concern? Of course, I could change synthetics every 5,000 but that is pricey.

Also, is the warranty affected by not changing oil every 5,000 mi. with synthetics or does Toyota honor the synthetic oil recommended interval?

As to the fossil fuel issue, as I understand it, spent regular oil gets reused. And as JDavies questions, what are synthetics made from?

Lastly, a comment: I won't use Mobil 1 as I do not patronize Exxon/Mobil products.
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post #14 of 17 (permalink) Old 12-03-2005, 10:23 PM
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Quote:
Originally Posted by DanMan32
I'd be very careful if I were you. Sure, there is a great chance that the oil and filter will stand up to Amsoil's change interval. But all they will clearly state regarding voiding manufacturer warranty is that the oil itself meets or exceeds specifications, thus will not void the warranty, but does not clearly state that extending the manufacturer's change interval won't void the warranty.

Besides, as I have been saying for quite a while, it isn't just the oil breaking down that is a problem, but combustion blowby contamination. Nobody has been able to answer to my satisfaction as to why contamination is not an issue. I understand oil breakdown perfectly, but even oil that stays brand new will get contaminated.
Here..Here..Definitely agree with that one Dan!

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post #15 of 17 (permalink) Old 12-04-2005, 03:04 AM
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http://autos.groups.yahoo.com/group/toy ... 050-04.gif

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US TSB EG050-04
December 20, 2004. ENGINE OIL SPECIFICATIONS. 2001-2005 Prius.
(Incorrect engine oil viscosity or improper fill level may result in a M.I.L. "ON" condition (most common Diagnostic Trouble Code P3191 "Engine does not start"). Use SAE 5W-30 API grade SL "Energy Conserving" oil and use proper fill quantity.)

-- Michelle Vadeboncoeur, mrv@kluge.net
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post #16 of 17 (permalink) Old 12-04-2005, 11:41 AM
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Quote:
Originally Posted by JDavies
... Just what is synthetic oil made from/of..? It feels like petro..it smells like petro..etc...
(I've used castor oil in 2 stroke race engines and olive oil in the kitchen.)
Most synthetic oils for internal combustion engines are poly alpha olefins. These are synthesized from ethylene which is in turn "steam cracked" from petroleum. In principle ethylene could be produced from most any hydrocarbons including plants, but at present crude oil is the cheapest starting point.

I hope this does not generally deter folks from synthetic lubricants; they do offer some clear advantages.

DAS
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post #17 of 17 (permalink) Old 12-04-2005, 12:05 PM
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"at present crude oil is the cheapest starting point."
***********************************************
So.. they take a $1 qt of oil and turn it into a $4 qt of oil..??
That sure makes my weekend..

2004, White, full package.
Scan Gauge,
Castrol Synth. oil @ 2500 miles.
Hey.. \"it's just a car...\"
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