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Finch
09-01-2005, 11:17 PM
Changing oil tomorrow in the 85 Nighthawk. Its air-oil cooled, takes 20w-50, uses the same oil for the tranny and has a wet clutch. Would synthetic or a synth blend be a bad choice? I love Mobil 1 Super Synth in my brand new toyota...but in a motor invented right around when vinyl died kinda worries me. Good/Bad?

MarcS
09-01-2005, 11:23 PM
Don't do it.

Synthetics can do "damage" in one of two ways. Synthetic base oils will cause seals to shrink slightly. Newer synthetics have additives that cause the seals to swell a bit to counteract this, but on an older bike with iffy seals to begin with, it might damage the seals. Secondly, synthetics often have superior additive packages compared to dino oils, and are better (ie, better cleaning) oils to begin with, and they can remove particulates that are plugging cracks/leaks in your seals. On a new motor, this isn't an issue since the synthetic will condition the seals and help them last longer than dino oil otherwise would, but on an old one where the damage is already present, synthetics can make it worse.

sanglant
09-02-2005, 12:28 AM
Changing oil tomorrow in the 85 Nighthawk. Its air-oil cooled, takes 20w-50, uses the same oil for the tranny and has a wet clutch. Would synthetic or a synth blend be a bad choice? I love Mobil 1 Super Synth in my brand new toyota...but in a motor invented right around when vinyl died kinda worries me. Good/Bad?


I agree with Marc on this one. I run synthetics in my bikes, but the Magna wasn't a big deal to me, since if it leaked, I'd just rebuild it. It didn't, but it was a possibility. I don't see the advantage of a synthetic being worth the potential trouble if you don't have the willingness/ability to do a rebuild.

Logan
09-02-2005, 12:37 AM
I wouldn't go synthetic with that old an engine for the reasons mentioned.

The main benefit of syns are extended change intervals, easier starting in very cold weather, and a little better engine cooling.

If you plan to stick to the recommended change interval, there's little added value.

If you want to try, you could get a syn blend & see how it works.

I'm running Quaker State Synthetic Blend 20w50 for high performance engines in my F650...runs real good on it. $3.00/qt

http://www.quakerstate.com/images/products/oil_synthetichighhorse.jpg

Finch
09-02-2005, 06:39 AM
Don't do it.

Synthetics can do "damage" in one of two ways. Synthetic base oils will cause seals to shrink slightly. Newer synthetics have additives that cause the seals to swell a bit to counteract this, but on an older bike with iffy seals to begin with, it might damage the seals. Secondly, synthetics often have superior additive packages compared to dino oils, and are better (ie, better cleaning) oils to begin with, and they can remove particulates that are plugging cracks/leaks in your seals. On a new motor, this isn't an issue since the synthetic will condition the seals and help them last longer than dino oil otherwise would, but on an old one where the damage is already present, synthetics can make it worse.

I'd always wondered why people always said synth in old motors would leak. This is the first time somebody has said why. thanks.

Regnaston
09-02-2005, 10:50 AM
I didn't undestand why they would leak either Finch. Thanks for th replies on this everyone. I learned something new today :-)