Group 3 syn, dino and seals...

[mikemc]

Hmmm. Just food for thought. Suppose I wanted the cold starting properties of a syn in winter, but I am fine with less expensive dino for the other 3 seasons. Would I be better off using a group 3 syn in the winter because I am thinking it is more chemically related to plain dino than a PAO? The idea being not exposing seals to 2 different base oils every year. Or is it irrelevant?

 

[JonS]

I used to think the same about group 3 being better for older seals. Group 3 has the same cold flow properties as a group 4 except they don't last as long. You should change them out in 5k or 3-4 months. How cold does it get in SE Kentucky? I went with Mobil 1 5w-30 in my '95 Jeep with small leaks and decided i would rather have an engine that starts at -25 and leaks, rather than one that is sealed up but starts hard. To my amasement, the leaks stopped.

 

[G-MAN]

quote:

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Originally posted by JonS:
I used to think the same about group 3 being better for older seals. Group 3 has the same cold flow properties as a group 4 except they don't last as long.

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Actually, this isn't the case. If we're talking about the neat base oil (not a finished motor oil), the typical Group III pour point is significantly higher than that of PAO (wax isomerate Group IIIs like Shell's XHVI are the exception). To get the pour point down in a finished Group III based motor oil requires the use of pour point depresents, which PAO doesn't need. Even then, the typical pour point for a Group III motor oil will be 10-15 degrees higher than that of most PAO based oils.

As for seals, Group III is almost as "bad" as PAO when it comes to seal swell. This is because virtually all the aromatics have been removed in the hydrocracking and hydrofinishing processes. It is the aromatics in Group I that promote seal swell. This is why any Group III based oil is going to also have some esters in it (or some Group I, as in the case of Shell Rotella T Synthetic) to ensure proper seal swell.

 

[Blue99]

Here is a post from last month in which members from Minnesota are cold starting at -25F with dino 5W-30.
dino 5W-30 cold weather starts

A key point is that even a new battery loses cranking power in subzero temps & a good battery is as important as the right oil.

 

[MolaKule]

Similar topic in similar thread:

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=005605;p=1#000014

 

[mikemc]

JonS said "How cold does it get in SE Kentucky?". It can get down to zero F or even a few degrees below in a brutal winter. This year it has not been below zero. I'm beginning to think I could run a really good dino with good flow properties all year and be ok.