Does anyone know if it's a good idea to put synthetic oil in an older Sportster? I've been told it may be to thin to provide adequate protection.

 

I'm running M1 20w50 syn in my 1999. How old is yours?

 

I am new to motorcycles, so I'm basing my opinion solely on my automotive experience. There are plenty of advantages to running synthetic oil. It lubricates better than conventional, you get better fuel efficiency by reducing friction and increased heat dissipation. Overall your engine works smoother and lasts longer.

 

Here we go again!

 

Ya what he said!!!!

 

It's fine to switch to synthetic. The only thing is that it sometimes causes the top end to get a little louder. There's the old myth that changing to synthetic in an older engine would cause it to start leaking due to the synthetic cleaning all the gunk out of the engine that's kept it from leaking already.

 

In My Humble Opinion, the biggest advantage to running synthetic oil in an air cooled motorcycle is its greater resistance to heat-related viscosity breakdown. Another oil thread? It is December, isn't it? There's a myriad of well-written, informative articles - Google's your friend.

Short answer - it's OK to run synthetic in anything you want to. If you want to understand why - there's ample reading material published on the web to address that question.

 

It's not really a myth, I've seen it happen more than once on older, high mileage (100,000+ miles) motors.

Conventional oil is created by natural means by biodegradation of living things/organisms over hundreds of years. Unlike synthetic oil which is made up of small, uniform molecules, conventional oil molecules are not uniform in size (some large & some small). When you have small imperfections in gasket seals, some of the large oil molecules present will lodge themselves in the crevices causing a seal and preventing the smaller ones to pass through. When you change to synthetic oil, the new oil will eventually displace the molecules of the previously used conventional oil and will flow through the imperfections and you now have leaks. This is not a common problem on new engines but on older engines with dried and cracked gaskets it can be.

No, synthetic oil doesn't cause leaks, but it can expose them if you have dried out or cracked gaskets.

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Synthetic oil gets into tighter groves, thats why they say it leaks, its like using a thinner viscosity oil. For example in my car that has 250k miles, it uses 10w30 but I use 10w40 synthetic not only because gaps have gotten bigger but also because synthetic gets in tighter groves. synthetic oil therefore might burn in your bike faster than non synthetic

 

Correct, and I probably should have explained it better like you did, but I had to run out into the plant, (I'm at work in a chemical plant), to take care of something slightly more important, so I said myth-> as in when the HD dealership used to tell all their clients that you couldn't switch the bike over.