synthetic oil

[Rob C.]

Hi All,
Could some one tell me if synthetic oil runs cooler than reg. oil.
Thank You,
Rob

[Michael S.]

Re: synthetic oil

Yes!

[Duke W.]

No!

Myth! Nor is it "more slippery" - another myth.

Scroll down for a recent oil discussion within the last couple of days.

Duke

[Gary S.]

Re: synthetic oil

Basic laws of physics and heat transfer say that they should run the same temp. Pass oil over/through/around objects at a set temperature and both dino and synthetic will run the same.

Gary

[Michael S.]

Re: synthetic oil

Real world experience for me! Synthetic oil runs a solid 10 degrees cooler in my 66 Shelby GT 350 during Vintage Races at the same track, same ambient temperature, same oil volume, same oil cooler, same temperature gauge, same filter, same time of year while running 300 RPM higher chip and turning a faster lap time than with Dino oil.

Same results with my Datsun 510 Vintage race car however the temperature difference is 5-7 degrees cooler. Maybe this is like the bumble bee actually flying? Basic laws of physics say dino and sythethic should run the same temperature. That is NOT the case for me in 2 real world applications.

[Michael H.]

Re: synthetic oil

Mike,

If Synthetic oil does indeed run cooler than non synthetic, I have to wonder if it's because it's not absorbing heat from engine parts as efficiently as conventional oil. The temp of oil is not just a result of friction during it's cycle through the system but also the fact that the oil carries off engine component heat as it travels over/through these components. It's possible that the synthetic oil does leave some of the component temp behind as it travels but I'm not sure this is actually a good idea. I'd like to hear more theories on this. Where's the Duke?

[Duke W.]

Re: synthetic oil

Vendors of synthetic oil claim lower operating temperatures and users offer anecdotal evidence, but I see no engineering basis to support these claims.

Assuming the oils used have the same viscosity at operating temperature, and a 5W-40 synthetic is in the same range as a 15W-40 mineral base at typical operating temperature, friction will be about the same. The second number specifies the range of viscosity at 212F.

Now if you use an oil with a lower high temperature visosity rating, -20 or -30, viscosity is lower so friction generated heat as the oil goes through the bearing is less, and this may be measureable in terms of slightly more power, but film strength is less and there is a greater chance of spinning a bearing, especially if temperature gets out of control due to inadequate oil cooling.

As far as any difference in heat capacity being a factor, that's a possibility, but I've never seen any data on the heat capacity of synthetic versus mineral oil, so I don't know if this is an issue or not.

Duke

[Michael H.]

Re: synthetic oil

Interesting that, the ability of some liquids to transfer heat is much the same as that of metal. In other words, the coefficient of heat transfer, or absorption, of a liquid doesn't necessarily have to be the same as another. Just like aluminum or copper that have the ability to absorb, dissipate or transfer heat much more efficiently than cast iron or steel, so do various liquids. I would like to know the different rates of transfer between petro oil and synthetic.

If synthetic doesn't absorb heat as quickly as petro oil, that means more engine component heat has to be removed through the engine cooling system.

I still use old fashioned oil so I'm not partial to either. Just curious.

[dick foehringer]

Re: synthetic oil

synthetic oil has all the hydorcarbon chains of equal length. regular oil has many fragments. so if you visulize a bunch of short, medium and long chains trying to align themselves in the bearing gap regular oil will have voids between the chains. synthetic has every gap filled. so one could argue that there is more surface area contact between the bearing surfaces han regular oil, thus better heat transfer. to me that is not the benifit. if you watch your oil pressure at idle with regular oil after 3-4000 miles the pressure will drop. thats because the molecule chains have broken down a lot since refining. synthetic chains do break down but they start with all equal length.

[Michael H.]

Re: synthetic oil

Thanks Dick. This does seem to make some sense, I suppose. I think it's time for me to learn about synthetic oil. I'm looking for info on the internet as we speak.

[Terry M.]

Check out BITOG.com

This site is to lubricants as we are to Corvettes

www.bobistheoilguy.com

[Michael H.]

Re: Check out BITOG.com

Thanks Terry. Looks interesting. I'll read it tonight and hopefully get into the 21st century on oil.