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#2309009 - 07/07/11 07:13 PM thicker oil causes valve seal damage (?)
ericthepig Offline


Registered: 12/26/06
Posts: 1648
Loc: Little Rock, AR
Found this post on the MMO forum -

"If you go thicker, you risk wearing out your valve guide seals at the least, and valves at the most. Staying with the recommended oil viscosity, except high mileage, seems to work well. I went 185K on 10-30W, and it still did not need additional oil between changes; but I smelled oil at startups near my exhaust. O/W, its running like a new truck, except with Lucas stabilizer added to high mileage oil. My engine is set, and just try to replace components with the best quality I can afford at the time (I get a few go wrong about every 75K, especially in mid-FL heat). Hopefully, Iíll have less go wrong now that Iím an MMO convert!!

Yes, thicker oil feels better for a brief time, but keep an eye on your exhaust at startup. You will soon see blue clouds coming from your exhaust!"

Any truth here ?
_________________________
'06 Mazda 6 (97k) - Pennz YB 5w20 for summer (1 filter/yr)
'98 Sienna - (87k) - Pennz YB 5w30 1 yr OCI (but only ~5k miles)

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#2309016 - 07/07/11 07:18 PM Re: thicker oil causes valve seal damage (?) [Re: ericthepig]
TurboTravis Offline


Registered: 07/26/07
Posts: 149
Loc: NY
Zero

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#2309025 - 07/07/11 07:39 PM Re: thicker oil causes valve seal damage (?) [Re: ericthepig]
Chris142 Offline


Registered: 06/05/03
Posts: 11471
Loc: apple valley, ca
Nope. Where do people get these ideas?
_________________________
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#2309026 - 07/07/11 07:40 PM Re: thicker oil causes valve seal damage (?) [Re: TurboTravis]
JOD Offline


Registered: 09/10/09
Posts: 3145
Loc: PNW/WA
Originally Posted By: TurboTravis
Zero


Disagree, completely.

If thicker oil doesn't place more stress on engine oil seals, then there are some basic laws of physics which are being re-written. Whether or not it 'matters' depends on the engine.

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#2309069 - 07/07/11 08:20 PM Re: thicker oil causes valve seal damage (?) [Re: ericthepig]
JoeWGauss Offline


Registered: 04/02/11
Posts: 175
Loc: Peachtree, GA
nonsense. But then again MMO is nonsense as well.

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#2309073 - 07/07/11 08:23 PM Re: thicker oil causes valve seal damage (?) [Re: ericthepig]
Astro14 Offline


Registered: 10/10/10
Posts: 4545
Loc: Virginia Beach
Without taking a side in the debate (I have no experience running overly thick oil...), I think I can explain the thinking:

A minute amount of oil has to get past the seals to lubricate the valve stem itself. Thicker oil will not get past the seals as readily as the recommended viscosity.

Ergo, less lubrication of the valve stems leading to the early demise of either stems or guides. Worn out stems will kill the seals and voila' - blue smoke.

The likelihood of this is unknown to me...depends on how critical the stem/guide lubrication is, how overly viscous the oil is for that application and how susceptible the stems/guides are to wear.

But I see the logic in the thought process...


Edited by Astro14 (07/07/11 08:26 PM)
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#2309083 - 07/07/11 08:33 PM Re: thicker oil causes valve seal damage (?) [Re: JoeWGauss]
TurboTravis Offline


Registered: 07/26/07
Posts: 149
Loc: NY
Originally Posted By: JoeWGauss
nonsense. But then again MMO is nonsense as well.


Gonna have to agree that MMO in gas/oil is a placebo-based cleaning experience

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#2309084 - 07/07/11 08:36 PM Re: thicker oil causes valve seal damage (?) [Re: JoeWGauss]
ericthepig Offline


Registered: 12/26/06
Posts: 1648
Loc: Little Rock, AR
Originally Posted By: JoeWGauss
nonsense. But then again MMO is nonsense as well.


Disagree. MMO has it's place for certain apps.
_________________________
'06 Mazda 6 (97k) - Pennz YB 5w20 for summer (1 filter/yr)
'98 Sienna - (87k) - Pennz YB 5w30 1 yr OCI (but only ~5k miles)

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#2309094 - 07/07/11 08:44 PM Re: thicker oil causes valve seal damage (?) [Re: ericthepig]
TurboTravis Offline


Registered: 07/26/07
Posts: 149
Loc: NY
Originally Posted By: ericthepig
Originally Posted By: JoeWGauss
nonsense. But then again MMO is nonsense as well.


Disagree. MMO has it's place for certain apps.


Door hinges, model car wheels..

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#2309098 - 07/07/11 08:46 PM Re: thicker oil causes valve seal damage (?) [Re: ericthepig]
Gokhan Online   content


Registered: 12/29/10
Posts: 1561
Loc: Los Angeles, California
Originally Posted By: ericthepig
Found this post on the MMO forum -

"If you go thicker, you risk wearing out your valve guide seals at the least, and valves at the most. Staying with the recommended oil viscosity, except high mileage, seems to work well. I went 185K on 10-30W, and it still did not need additional oil between changes; but I smelled oil at startups near my exhaust. O/W, its running like a new truck, except with Lucas stabilizer added to high mileage oil. My engine is set, and just try to replace components with the best quality I can afford at the time (I get a few go wrong about every 75K, especially in mid-FL heat). Hopefully, Iíll have less go wrong now that Iím an MMO convert!!

Yes, thicker oil feels better for a brief time, but keep an eye on your exhaust at startup. You will soon see blue clouds coming from your exhaust!"

Any truth here ?

I don't think the viscosity of oil affects the endurance of the valve seals that much. Most valve seals are metering type and they meter the oil that passes through the seal and for thinner viscosities, more oil will pass through. But there should be a descent oil film between the seal and stem with any viscosity. These seals are working in boundary-lubrication regime I believe and even in the boundary-lubrication regime, I think thicker viscosity is better for wear. I think the failure of the seals happens mostly due to failure of the rubber thanks to heat hardening.

All said, I've replaced my valve-stem oil seals about 700 miles ago, which was a lot of difficult and tiresome work. A shop would probably either not do it or charge a small fortune.

Here is how they look like. Note that the inside of the Viton seal is metal-clad:

_________________________
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#2309112 - 07/07/11 08:57 PM Re: thicker oil causes valve seal damage (?) [Re: Astro14]
Trav Offline


Registered: 11/20/06
Posts: 9987
Loc: MA, Mittelfranken.de
Yes that the logic but given the wide tolerance even heavy oils can provide enough lubrication to the stems.
Many engines run heavier oils for the life of the engine without issue or stem/ guide failure, e.g. Diesels and Euro engines.
Just a guess on my part but i would think with emission regulations being what they are manufacturers would want to keep oil consumption through the guides to a minimum.
Many guides are bronze and tend to hold lube.


From SKF.
Quote:
Oil metering to the valve guide /
s tem interface is the prime function of a
valve stem seal. Although the requirements
for each engine differ according to the design
parameters and operating conditions, the oil
metering rate is generally within the range
of 0.1 - 1.0mg per valve per hour.
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#2309136 - 07/07/11 09:15 PM Re: thicker oil causes valve seal damage (?) [Re: ericthepig]
Steve S Offline


Registered: 01/20/03
Posts: 18449
Loc: East of IGO
Thick oil is the cause of all evil. Says so on oil 101.
_________________________
Why do people post I want the best for my car,,, When there isn't anything that is the best on the car to begin with.

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#2309137 - 07/07/11 09:16 PM Re: thicker oil causes valve seal damage (?) [Re: Chris142]
Steve S Offline


Registered: 01/20/03
Posts: 18449
Loc: East of IGO
Originally Posted By: Chris142
Nope. Where do people get these ideas?
approved
_________________________
Why do people post I want the best for my car,,, When there isn't anything that is the best on the car to begin with.

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#2309150 - 07/07/11 09:29 PM Re: thicker oil causes valve seal damage (?) [Re: TurboTravis]
R2d2 Offline


Registered: 12/08/08
Posts: 527
Loc: New York, L.I
Originally Posted By: TurboTravis
Originally Posted By: ericthepig
Originally Posted By: JoeWGauss
nonsense. But then again MMO is nonsense as well.


Disagree. MMO has it's place for certain apps.


Door hinges, model car wheels..


Lmao exactly!
_________________________
2014 Acura MDX
2011 Honda Accord V6 coupe

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#2309219 - 07/07/11 10:39 PM Re: thicker oil causes valve seal damage (?) [Re: Gokhan]
TFB1 Offline


Registered: 09/03/10
Posts: 2622
Loc: VA
Originally Posted By: Gokhan
Most valve seals are metering type and they meter the oil that passes through the seal and for thinner viscosities, more oil will pass through. But there should be a descent oil film between the seal and stem with any viscosity. These seals are working in boundary-lubrication regime I believe and even in the boundary-lubrication regime, I think thicker viscosity is better for wear. I think the failure of the seals happens mostly due to failure of the rubber thanks to heat hardening.

All said, I've replaced my valve-stem oil seals about 700 miles ago, which was a lot of difficult and tiresome work. A shop would probably either not do it or charge a small fortune.


Yup most valve stem seal failures are related directly to heat, no surprise when they fail at 200K+ miles... Mostly the type of material the seal is mfg'd from dictates it's longevity... The the early Ford Modulars used a seal that failed before 100K mi(another engine that they are a PITA to repl, got my T-shirt), begnning '96 an improved seal was introduced that generally lasts the life of the engine...

New stem seals can a major difference, I've seen OHC engines that were using a quart in 200mi, improve to less than a quart usage in 3K mi...

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