Ken's corner #3: Synthetic vs. conventional oil

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Ken's corner #3: Synthetic vs. conventional oil

Postby ken.lagarec on Sat Nov 09, 2002 1:46 am

The great debate of the motoring scene of the late 20th century spills into the 21th century: synthetics vs. dino juice. Is it worth it? Basically I'll take this opportunity to talk about oil and get down to the point. Again, these are my opinions, so don't take them for more than that and feel free to comment!

1. What are they?

Conventional oil (aka dino juice) is based on petroleum products. They are derived from naturally occurring molecules hence are not synthetic. Keep in mind that there are also other types of oil the are not synthetic and not based on petroleum, such as corn oil, and other vegetable oils used for cooking. In fact, some vegetab;e oils were/are still used as motor oil, although petroleum oil is never used for cooking unless you're really hard core.

Synthetics on the other hand are, as there name implies, synthesized in laboratory by chemical reactions, to produce a polymer that has properties suitable to be used in an engine for lubrication purposes.

Conventional is cheaper than synthetics 'cause the extraction is still cheaper than the synthesis. That may change though as cheaper synthesis methods are developed and larger volumes are sold.

2. What difference is there?

Bear in mind that point that is essential here is what do they do? A four-stroke engine doesn't burn oil for power, so it isn't necessary per se, but an oil is useful to extend the life (and performance) of the engine by:
a. lubricating - makes the pistons and valves go up and down easier. A low viscosity is needed here. Proper lubrication reduces wear.
b. sealing - provides a seal for the combustion chamber. With standard clearances and no oil, a lot of gases would escape around the piston rings. Oil helps prevent this blow by. A high viscosity is needed here
c. cooling - transfers heat away from the pistons using things like oil suqirters (littles holes in the con rod to let the oil "squirt" onto the base of the piston and cool it. Oil is a very important component to the cooling system of an engine.
d. cleaning - removes harmful gases (specifically acidic gases), particles (metal shavings, etc) and deposits (carbon) from the combustion chamber to get optimal running conditions.

A good oil must do all this and:
e. withstand the heat. A lot of things decompose under extreme heat. An oil must withstand the heat and not change its properties over time.
f. withstand the shearing forces (as a piston goes up and down it tends to shear the oil and possibly break the molecules that make up the oil, thereby changing its properties). This is even more significant in gear oil where the shearing and compression forces in a transmission or differential are huge.
g. operate properly at low (-20 C) and high temperature (~100-120 C)

Conventional oils do these things well. The problem is with e., f. and g. A synthetic oil is taylor MADE to have these characteristics and are nearly always better than conventional oil:
e. Synthetics can withstand much higher temperature than conventional before coking (basically burning the oil and changing it into carbon residue that gums up). For this reason, a turbocharged car should always use synthetics as the turbo transfers an enormous amount of heat to the oil, and often causes cokin in the oil lines and the turbo bearings. Eventually they clog up and the turbo is deprived of oil and seizes or burns through a seal.
f. Again, synthetics can withstand greater shearing forces. Although a conventional oil might work, a synthetic will not degrade as quickly in time. This is the primary reason why you can have longer oil changing intervals when using synthetics. They don't decompose (because of heat and shearing) in time as much as conventional oils. The filter however should still be changed as frequently to get rid of all the debris that it filters out.
g. A very important point. Oils are rated based on their viscosity at 0 C. This gives them a 10W, 20W etc rating. 10 weight oil has a viscosity between XX and YY at 0 C, 20 is between YY and ZZ etc. Viscosity however decreases with temperature, so a 10W oil is actually very thin at the normal operating 100 C and won't protect your engine much in those conditions (in particular won't seal). A 50W has the proper viscosity at 100 C but won't flow well at low temp, so until your engine temp is up, it will not provide godd lubrication, therefore causing a lot of wear and tear. So they invented multigrade oils. E.g. 5W30 this means it has the viscosity of a 5W oil at 0 C (good for protection during startup) and is not more fluid than a 30W oil would be at 100 C (also provides good protection at normal operating temp). To do this with conventional oils (the 10W, 20W etc are based on conventional oils), oil companies start off with a base of 5W oil and add stuff that prevents it from loosing too much viscosity at high temp. Often, those additives aren't as temperature stable as the oil base and they break down in time sooner, transforming your 5W30 into 5W and sludge. So you have to change your oil frequently. Synthetics inherently behave like multigrade oils. They have very different viscosity vs. temp behaviours such that, in their simple form with no additives, they can have the same viscosity properties as a 5W30 oil. Less additives means they don't have that achille's heal and resist temperature better. On top of that, you can get synthetics that are "energy conserving" (often 0W30) such that they have low enough viscosity that they don't rob the engine of much power but provide good protection at either low or high temp. You can't find a 0W conventional oil (at least I think you can't).

3. Problems and misconceptions

So why not always use synthetics?

a. It's often mentioned that synthetics are thinner than conventional oil and can seep though holes where conventional oil can't. I don't quite understand that concept (what the hell does it mean?). A 5W30 is a 5W30. If it was thinner, it would be a 0W?. A 15W50 synthetic is much thicker than conventional 5W30. Beleive me, I just put some in my car tonight. The viscosity of the liquid will determine if it can or can't seep though an opening so why would a synthetic rated the same as a conventional flow differently ? (OK there are different kinds of viscosities, but I don't think there's that much of a difference).

b. In the eighties, when synthetics were becoming more popular, there was a problem with switching to synthetic oil which would cause leaks. The joints (gaskets, etc) would shrink slightly with synthetics (wouldn't soak it up as much), causing leaks. This was quickly identified by motor oil manufacturors and FIXED. Modern synthetics oils will swell gasket the same as conventional, so there won't be that problem anymore.

c. People recommend to break in an engine using conventional oil and then switch to synthetic. If you want. I'll just say that Porsches come from the factory with Mobil 1 (synthetic). BMWs come from the factory with Castrol Syntec (synthetic). Maybe if the tolerances aren't high, it's necessary to break in the engine with dyno for some unknown reason, but in today's times, processing tolerances are very high compared to 30-40 years ago and I bet you can just go straight to synthetics.

d. People say you can't mix synthetics with conventional or between brands. BS. One of the criteria for getting API (SJ now?) classification is that it must mix with any other oil of the same classification. Synthetic manufacturers will say it's OK but it reduces (dilutes) the special properties of the synth so it shouldn't be done. But they themselves do it by selling blends. And I'm willing to bet that their blends are just 50% of one and 50% of the other. Not some specially concocted mixture. Anyway. So if your using synthetic oil and you need some and you're in nomansland and they only got Brand-X dino juice, don't worry, it won't seize your engine unless brand X is water based...

e. Detergents. Modern oils, both conventional and synthetics have lots of detergents to clean the engine as it runs (same as fuel, that's why you don't really need those miracle potions they sell). Synthetics are usually high-end and they clean very well. Compared to el-cheapo conventional, there may be a huge difference. But I'm pretty sure regular Castrol has the same types of detergents. People say if you switch to synthetic, it will clean you engine so good that deposits might disloge and clog up smaller holes. It might. But that can happen if your using a highly detergent conventional oil too. If you have that many build ups, your engine is in rough shape and you probably don't wnat to spend the extra cash on synthetics anyway. A well kept, properly serviced engine should have no trouble when switching to a highly detergent oil. Just change your filter really quickly the first time as it might get much more debris that it usually does.

Should you switch? Synthetics are a better oil for extreme conditions of heat and stress. If you turbo, you should definitely use synthetics. If you drive your engine hard, you should think about it seriously. If you drive an auto Corolla that switches at 2k RPM you could think about a 0W oil to save fuel. Essentially, it's a better oil. It's made to be better... It costs more but you can get longer service (double? probably more) so it's not as bad as it seems, plus thats $25 twice or three times a year for peace of mind. If you're not willing to spend that on your car, then you should drive a nice reliable Toyota (and get gangbanged by their service department if you dare to go there) and forget about neo240sx.ca

I talk too much. I don't even remeber what I wrote but I'm too lazy to read it over. That's your task. Sorry for the typos if there are any.

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Postby 13th-Angel on Sat Nov 09, 2002 6:54 am

ditto :shock:

very informative, thanks!
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Postby Black Madgic on Sat Nov 09, 2002 3:26 pm

That's some good info Ken.

As for the types of viscosity. There are two types, one is absolute and the other is kinematic. Absolute is commonly known to be viscosity, but it deals more with stationary fluids. Where as kinematic is more related to fluid in motion. Viscosity does not change much with pressure (ie a 50x difference will cause roughly a 10% change). However there is a very large change with temperature. So from this viscosity is related to the dendsity of a fluid (as temperature and pressure have an effect on density). This is seen through The Reynolds Number eqautin. I'm not going to show what that is unless someone wants to see it.

So an oil of the same weight (I am assuming this means density), between dino and synth could have much different viscosities. By thinner I am assuming that this is in reference to the densities (mass over volume). I would think then that the synth would be designed to flow better at all temperatures so its kinematic viscosity would need to be lower.

My head hurts now from looking at that damn fluid mechanics text \bok now.
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Postby ken.lagarec on Sat Nov 09, 2002 8:52 pm

Shaun: Weight doesn't actually refer to the mass weight. Maybe historically but not anymore. It's more of a designation of viscosity. As in a 10W, known as a 10 weight. That's what I meant by weight. Synthetics and conventionals are given a weight rating i.e. 5W30 based on their viscosities at 0°C and 100°C :arrow: might I say that's mighty hot.

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Postby Black Madgic on Sun Nov 10, 2002 3:39 am

Ken, I was trying to give a bit of a description of viscosity. The mass weight of oil that you put into an engine won't really have an effect on it. its more the volume of oil that you put into it.

I understood what you meant by weight, I guess I worded myself wrong. I was also staring into a fluid dynamuics text for too long...
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Postby Nismo on Sun Nov 10, 2002 4:45 pm

Ken, thanks for clearing up alot of the bull associated with synthetics.
I think I am gonna give it a shot in my car. I was always reluctant because of all the rhumors you hear, but what you said makes alot of sense. I am still on dino juice, but I do oil changes every 2500kms... so I think the engine is pretty clean and I will be pretty safe to switch over to the dark side.

Good Thread. 8)
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Postby 13th-Angel on Sun Nov 10, 2002 5:41 pm

Wow, you've been on non-synth this entire time? whoa... both my SOHC and my DOHC had Synth running on it. Castrol on the SOHC, and Mobil 1 on the DOHC. :)
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Postby Nismo on Sun Nov 10, 2002 7:01 pm

Yep... I run Mobil 1 dino juice.
But I guess I will upgrade to the good shit now.
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Postby ken.lagarec on Sun Nov 10, 2002 7:23 pm

Nismo wrote:Yep... I run Mobil 1 dino juice.
But I guess I will upgrade to the good shizim now.


Are you sure it's not synthetic? I thought all Mobil 1 products were synthetic... The one I use sure is.

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Postby frostman on Mon Nov 11, 2002 12:28 pm

no mobil does make a conventional (never seen it in canada) i took a trip to calgary a few years ago. i cut through the us and had to get oil . so i stopped at a pep boys, grabbed a mobil 5w30 and headed to the car. my gf asked me why the oil was in a diffrent looking bottle, i being the smart guy said "because were in the us and everything is fin backwards here". then she says to me "ok stupid then why dosnt it say synthetic on the bottle" :oops: guess she is smarter than i thought (thats why she has an areo degree and not me)
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Postby ken.lagarec on Mon Nov 11, 2002 7:21 pm

You're right (at least partially). I checked their website and Mobil does make a "Drive Clean" line of oil that are conventional. But it still seems Mobil 1 is their synthetic only line. Was the stuff you got in the state Mobil 1 or just made by Mobil? I'm not trying to argue, I just want to know...

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Postby Nismo on Mon Nov 11, 2002 7:26 pm

It might just be plain Mobil and not Mobil 1. I am not 100% sure.
But what I can tell you is that it comes in huge drums with the Mobil logo on it at the mechanic's shop, and they just pump it out of there. It might not be available at your local crappy tire.
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Postby FrEaK on Tue Feb 03, 2004 6:16 am

I was under the impression Mobil 1 was a super refined dino oil to start with. If we are refering to fully synthetic oils i believe there are only a full that can actually make that statement.

As far as Mobil 1 goes, I used it for a couple years and recently switched to Amsoil.

Needless to say i was impressed.

I don't know if your meber have seen this site, but enjoy the read anyways...

Mobil 1 vs Amsoil

http://www.authorized-amsoil-dealer-for ... sults.html

http://www.oilsandlube.com/they_say_not ... ms_mob.htm

http://www.syntheticoildealer.com/royle/supersyn.htm

http://www.bestsynthetic.com/mobil1.shtml

http://www.searchforparts.com/important ... l_one.html

Amsoil vs Other "Synth" Oils

http://www.authorized-amsoil-dealer-for ... dynometer/



Most of these links are similar in information but are different suppliers, some of them probably Amsoil biased, but the numbers seem to prove the difference...


As i recal Amsoil is slightly cheaper then Mobil, so the next time you change your oil, give it a shot, see if it's right for you...
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Postby frostman on Tue Feb 03, 2004 12:50 pm

Interesting, I used amsoil for years in my gsxr. Last summer I switched to bel-ray because they did not have any amsoil in stock. What a difference the bel-ray made. Gone were the missed shifts, no more snap engagements when i fluttered the clutch, and the valves quietened down a bit.

Now i know comparing a bike engine to a car engine that does not make much sense. So i will ad a bit on a friends Chevy 4X4. He switch to amsoil years ago from conventional, noticed a big improvement in power and fuel mileage. A few weeks ago, we bought a case of royal purple. After switching to that, he has not stopped raving about how great the stuff is. I will be trying it im my sentra next weekend when i get the oil changed. Considering the price difference of about $4 a bottle makes my future decisions easier
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Postby S13GG on Tue Sep 25, 2007 7:06 pm

http://www.animegame.com/cars/Oil%20Tests.pdf

^cut/pasted from a chat thread into a stickied tech thread
Last edited by S13GG on Tue Sep 25, 2007 9:03 pm, edited 1 time in total.
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