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Joined: Dec 26, 2007 Posts: 1284 Location: Scottsdale, Arizona
Posted: Sun Jan 29, 2012 1:45 pm Post subject: Old oil seals vs. synthetic oil
Heard the tale lots of times about how using synthetics causes old oil seals to leak. Always figured it was BS. Well, it may not happen in all cases, but it's not totally BS, either. Less than 100 miles after switching my 500/4 to synthetic, all three oil seals under the sprocket cover started leaking, as well as one of the O rings that seals the oil pump to the crankcase. Easy enough to fix, but a huge, messy PIA.
Joined: Oct 02, 2006 Posts: 2051 Location: New Britian, CT
Posted: Sun Jan 29, 2012 1:58 pm Post subject:
I was told that if I was to run synthetic on my CB350, to replace the old seals (original to the bike), with new seals. What this mechanic told me, and this gentleman is an old time honda dealer, that the synthetic, will seep into the seals, but the old seals get hard, so they won't be able to hold a seal with the synthetic.
Joined: Dec 26, 2007 Posts: 1284 Location: Scottsdale, Arizona
Posted: Sun Jan 29, 2012 2:02 pm Post subject:
MR.CHocko wrote:
I was told that if I was to run synthetic on my CB350, to replace the old seals (original to the bike), with new seals. What this mechanic told me, and this gentleman is an old time honda dealer, that the synthetic, will seep into the seals, but the old seals get hard, so they won't be able to hold a seal with the synthetic.
Apparently, that's exactly what happened. Oh well - it's probably a good thing to find marginal oil seals now, rather than when they really start pumping oil.
Joined: Sep 26, 2011 Posts: 32 Location: Connecticut USA
Posted: Fri Mar 09, 2012 6:08 pm Post subject:
I am going to try running Mobil 1 synthetic oil for high mileage vehicles which has seal conditioner. I like to get an oil that I can run in my 4 stroke Honda as well as the gear boxes of my 2 stroke Suzukis. Suzuki calls for a 20w-40 oil which is almost non existent, I have used 10w-40 with no problem so far, so the Mobil 1 High Mileage is 10w-40.
Joined: Dec 26, 2007 Posts: 1284 Location: Scottsdale, Arizona
Posted: Sat Mar 10, 2012 6:07 am Post subject:
Mat wrote:
I am going to try running Mobil 1 synthetic oil for high mileage vehicles which has seal conditioner. I like to get an oil that I can run in my 4 stroke Honda as well as the gear boxes of my 2 stroke Suzukis. Suzuki calls for a 20w-40 oil which is almost non existent, I have used 10w-40 with no problem so far, so the Mobil 1 High Mileage is 10w-40.
Matt,
For the 2-stroke gear boxes, you're much better off using a product like Bel Ray Gear Saver, or even type F ATF. I really suggest not using any synthetic of any viscosity in that gear box, unless it meets JASO MA specs. A modern motorcycle gearbox oil is much better for the gears than 20W40 motor oil. Those products weren't available way back when, and hypoid gear oil for car differentials isn't the way to go in the gearbox, either. That's most likely the reason 20W40 was specified.
Stu
Last edited by Bikegeezer on Sat Mar 10, 2012 6:14 am; edited 1 time in total
Joined: Feb 23, 2007 Posts: 1045 Location: Orlando, FL
Posted: Sat Mar 10, 2012 10:28 am Post subject:
Bikegeezer wrote:
KirkN wrote:
So, what if you just switch back to non-synthetic? Do the seals start functioning again? Or did the synthetic somehow permanently alter the seals?
Hmm......
The seals are just old, hard, and worn. The best way to approach the issue is to replace the seals. I did that, and the leakage stopped.
Stu
Well, naturally. But, for the sake of the "synthetic oil causes seals to leak" debate, it would be interesting to know the results.
I mean, "the seals are just old, hard and worn" was a true statement before the swap to synthetic, and yet they sealed! So, did the synthetic cause them to get older, harder, more worn, because that seems unlikely? Or does synthetic just sneak past such seals when non-synthetic does not, because then the fix would be to just swap back to non-synthetic rather than replacing a bunch of seals? Or does synthetic somehow do irreversible damage to the seals, as in, once-it-starts-to-leak-w-synthetic-theres-no-going-back, because then you'd HAVE to replace the seals?
Just tryin' to add some experimental evidence to the claim - BS or not?
So, what if you just switch back to non-synthetic? Do the seals start functioning again? Or did the synthetic somehow permanently alter the seals?
Hmm......
The seals are just old, hard, and worn. The best way to approach the issue is to replace the seals. I did that, and the leakage stopped.
Stu
Well, naturally. But, for the sake of the "synthetic oil causes seals to leak" debate, it would be interesting to know the results.
I mean, "the seals are just old, hard and worn" was a true statement before the swap to synthetic, and yet they sealed! So, did the synthetic cause them to get older, harder, more worn, because that seems unlikely? Or does synthetic just sneak past such seals when non-synthetic does not, because then the fix would be to just swap back to non-synthetic rather than replacing a bunch of seals? Or does synthetic somehow do irreversible damage to the seals, as in, once-it-starts-to-leak-w-synthetic-theres-no-going-back, because then you'd HAVE to replace the seals?
Just tryin' to add some experimental evidence to the claim - BS or not?
I don't think the synthetic oil damaged the seals although it might have "cleaned" the seals causing marginal seals to leak. Let me try to explain. Petroleum oil over time will leave a thin layer of sludge that can work as a "stop leak" for seals that are in their beginning stage of failure. As the seal continues to wear it eventually leaks. So the experiment would have been to clean the parts of any residual deposits and see if they leak with the original oil.
Joined: Dec 26, 2007 Posts: 1284 Location: Scottsdale, Arizona
Posted: Sun Mar 11, 2012 6:31 am Post subject:
Both of you guys have valid arguments, both of which I've heard before. But frankly, I'm not interested in expending the time or effort to find the answer to either. A seal in good condition on an undamaged shaft should be able to prevent leakage of any lubricant - synthetic or not. If I went back to Dino Juice and the seepage stopped, it would be only a matter of time before it returned, because either the seals were weak, or possibly a shaft was scored. Maybe both. Replacing those seals gave me the opportunity to also inspect for and correct any shaft damage. BTW, anyone who's ever used those engine oil stop leak products - the ones that soften and swell old seals - can tell you that IF it works, it's only a temporary fix, like just long enough to sell the vehicle. BTDT.
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