Why can synthetic pcmo last longer for a oci?

[Zeus103363]

What makes a synthetic last longer in the sump? Most of todays synthetic are a blend of group 3 &4 depending on the brand. Mabe they are just a straight group 3 base oil. I have always been a firm believer in using synthetic, but lately as the cost of everything has been rising, the price of dino is looking more attractive. There really isn't any additive in synthetic pcmo that Dino doesn't have so it can't be the additive packages that gives synthetic it's bang for the bucks we hand over for a quality synthetic. I have looked at numbers and my own uos's with nothing conclusive other than a recomendation to " go a few more thousand miles on that oil".

 

[dubie2003]

I have not researched this yet but I wonder if the TBN is higher in Syns since they will get the full use of that added TBN over the usually longer OCI?

Defiantly is a good question and will be something that I think and read about for the next few days.

 

[JOD]

This quick answer is that fewer aromatic hydrocarbons gives hydrocracked and severely hydrocracked base oils more effective oxidation inhibitor action, which in turn means that oils with synthetic base oils will last longer, all things equal. Of course, all isn't equal, and the amount/type of additive also makes a difference.

Add into that the fact that the best GII and worst GIII base oils have nearly identical physical properties, and that the new SN/GF-5 regs have more strict requirements for oil stability, even today's conventional oils will work for some fairly long OCI's (certainly as long as most people on here are comfortable running, and within the OEM recommendations). In short, I wouldn't assume that one oil is more suitable for a longer OCI just because it's synthetic and another oil is conventional. That's just not the whole story.

 

[Tom NJ]

Originally Posted By: JOD
This quick answer is that fewer aromatic hydrocarbons gives hydrocracked and severely hydrocracked base oils more effective oxidation inhibitor action, which in turn means that oils with synthetic base oils will last longer, all things equal. Of course, all isn't equal, and the amount/type of additive also makes a difference.

Add into that the fact that the best GII and worst GIII base oils have nearly identical physical properties, and that the new SN/GF-5 regs have more strict requirements for oil stability, even today's conventional oils will work for some fairly long OCI's (certainly as long as most people on here are comfortable running, and within the OEM recommendations). In short, I wouldn't assume that one oil is more suitable for a longer OCI just because it's synthetic and another oil is conventional. That's just not the whole story.


Well said.

Tom NJ

 

[mechtech2]

I think it's even simpler to say that the full synths don't thin or thicken as much over the long haul.
They are better concerning shearing. With a timing chain, this is more pronounced as a factor.

 

[Zeus103363]

Originally Posted By: JOD
This quick answer is that fewer aromatic hydrocarbons gives hydrocracked and severely hydrocracked base oils more effective oxidation inhibitor action, which in turn means that oils with synthetic base oils will last longer, all things equal. Of course, all isn't equal, and the amount/type of additive also makes a difference.

Add into that the fact that the best GII and worst GIII base oils have nearly identical physical properties, and that the new SN/GF-5 regs have more strict requirements for oil stability, even today's conventional oils will work for some fairly long OCI's (certainly as long as most people on here are comfortable running, and within the OEM recommendations). In short, I wouldn't assume that one oil is more suitable for a longer OCI just because it's synthetic and another oil is conventional. That's just not the whole story.


That part about the best GII and the worst GIII being nearly identical is my reasoning for second guessing my oil choice. I really think its time for there to be a clear defining requirement for synthetic motor oils that either proves synthetic is superior or drop the synthetic from the advertising.

 

[dave1251]

Originally Posted By: Zeus103363

I really think its time for there to be a clear defining requirement for synthetic motor oils that either proves synthetic is superior or drop the synthetic from the advertising.


You can not prove brand X is superior to brand Y unless brand X meets performance requirements that are required for your engine. I am not talking about just warranty requirements, I am talking about if your engine is unique and will self destruct if you do not use brand X or use a brand of motor oil that preforms as well or better than brand X. This is my argument that against synthetic is better for your engine unless your engine is operating in a very extreme operating environment whether this is due to being in the arctic circle or due to engine modifications. Not feelings.