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Maintenance & Repair Synthetic motor oil
8536 messages, Last post on Nov 21, 2009 at 9:34 AM
You are in the Maintenance & Repair Forum. Your Host is mr_shiftright
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Replying to: Mr_Shiftright (Nov 09, 2009 5:17 pm) 
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I did have a long talk with my Subaru service advisor (they have "stellar" classification from Subaru) and he warned me that as soon as I switch to synthetic oil, I can expect more oil consumption as apparently it works past the seals. He was not sure how long this additional consumption would continue. My workaround is to use a "uplevel classification" conventional oil and change it every 3K miles (as my Subie's a turbo, Oil's required to be changed every 3750 miles). So far, the oil coming out of Subie's engine is less dirty than from my former Malibu Maxx or Toyotas for equivalent mileage changes.
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Replying to: kurtamaxxxguy (Nov 17, 2009 10:59 am) 
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Replying to: kurtamaxxxguy (Nov 17, 2009 10:59 am) Unless Subaru uses gaskets and seals composed of material that is grossly inferior to what is used on every other car sold in the States, then your Service Advisor is speaking either from person bias or he was seriously misinformed. |
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Replying to: Mr_Shiftright (Nov 17, 2009 11:02 am) When synthetics are introduced, the better ones clean up the varnish. If the seals and gaskets are cracked because they dried out, the synthetic will penetrate and could cause some leaking. Also when the nooks and crannies are cleaned out, the synthetic can now get in there like it was supposed to. This can all cause a noticeable increase in initial oil intake, and usually stops by the second oil change.
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Replying to: timvipond (Nov 17, 2009 1:21 pm) Nor have I ever observed synthetic ever doing anything funny to gaskets during a tear down. Given such real feedback on so many varieties of cars, I personally feel confident to advise people not to worry about this. My opinion is that this worry about synthetic causing leaks came from a confusion between "causation" and "correlation". In other words, they were tinkering with an old car, or reviving it from storage, and it started leaking some oil or burning it---but they had done so many other things to the car, or just starting using it again, or were new owners. The only engine I tell people not to use synthetic oil in, is a Mazda rotary, based on what I've studied on that matter. |
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Mazdatrix discussion of not recomending synthetic oil in rotaries |
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Thanks for posting that link. The best laugh I've had today. I cant' believe that someone would actually write that stuff. And that anyone with knowledge of synthetic oil would take it seriously. "The ones that do not burn clean can leave residues of various substances (like ash? plastic? non-organic sand?) that accumulate until the spark plugs foul, or a seal sticks -- could be apex seal, side seal, corner seal, or oil control ring. The normal consequence of a stuck seal is an engine tear down." Chemical synthetic oils are not made with impurities that would form ash, where would the plastic come from?, non organic sand?. Chemical synthetic oils are made from pure chemicals synthesized from pure small carbon molecules. Of course petroleum oils could contain some of these components as they are made directly from crude oil. "In the many years we have been involved in rotary engines, we have NEVER had a problem with GOOD petroleum based oils. They work fine! They are less expensive than synthetics. (We use Castrol 20-50 GTX). They burn clean, etc. etc." Yeah right. There is no scientific evidence that supports their claim of cleaner burning. Does anyone really think that petroleum based oils with thousands of different components burn cleaner than pure chemical synthetic oils? Burn some yourself and see which burn cleaner and leave the least residue. "We are not chemists, and we do not have the time, $$'s, nor inclination to do 100K mile tests of various synthetics in rotary engines." Understatement of the year! Of course Mazda and oil and additive companies do the tests. We did when I was a chemist at Shell. When in doubt ask the vehicle manufacturers and the oil companies. Not the internet chat rooms. I posted a tech bulletin that covered all of this but it was deleted. In that bulletin "MAZDA RECOMMENDATION: Mazda Engineering recommends the use of designated gen- uine engine oil and the following guidelines: • Engine oil should be changed regularly. • Only designated genuine oil be recommended to customers. • Under severe conditions, oil should be changed at 5,000 km or every 6 months. The Mazda owner’s manual for the RX8 models with the RENESIS engine calls for the use of SAE 5W-20 engine oil that meets API SM/SL and is ILSAC rated. However, it does not specify what type of oil to use or issue any warnings about the use of synthetic engine oil.
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