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Synthetic vs. conventional oil

Old 05-12-03, 02:25 PM
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Synthetic vs. conventional oil

Lots of us have been back and forth on what is the most perfect oil, but I found these posts from Mr. Hubert Otlik and Mr. Ali Haas on another forum. They have some info I have never heard before and do seem to know what they are talking about. So here below is more fuel for the fire



Brian Willis has a lot of good info on an earlier post. However there are some oil misconceptions outstanding. The biggest one is that thicker oil is better. False. Higher speed turbines use thinner oil. Lubrication is not what you feel rubbing that oil between your fingers. Lubrication in engines is oil FLOW between moving parts.

The general saying that 90 percent of engine wear and tear occurs in cold engines is close to the truth. The most basic viscosity needs are defined by a pressure of 10 PSI per 1,000 RPM at operating temperature. My 575 M manual states the target pressure is 74 PSI at 6,000 RPM. The oil supplied with the car gives me about 80 PSI at 2,000 RPM, way too high. This is with around the town driving. I am sure that on the racetrack at full power and a hotter engine this thicker oil is fine. For my usual driving however, the thicker oil is causing more engine wear.

The manual of my old 550 Maranello gave only Shell Helix Ultra 5-40 for all uses. Oils are not that versatile. For around town use a thin oil, for the track use a thicker one. The new 575 manual states that the oil should be 15-50 for racing and 0-40 for around town. They are finally making more sense.

Oils are getting thinner. Ford now supplies most cars with 5 - 20 oil, previously it was 5 - 30. If you test different oils in your engine you will notice the engine oil temperature decreasing with thinner oils. At some point the next thinner oil will result in the engine temperature starting to go back up. This lowest temperature point is that with the least friction.

A friend recently changed from Mobil 1 15-50 in his big SUV to Penzoil 5-20 and went from 10 to 13 MPG around town. There was a slight decrease in engine oil temperature. The savings was also in cost for oil. His biggest enjoyment was the increase in get up and go power. For time trials all Indy and Stock cars use thinner oils to get more power. These oils will not stay thick enough for a long hot race but around the town driving is nothing like racing.

The last misconception I will tell you about is that those oil viscosity numbers on that oil can are not what you think at all. For example, Penzoil 100W EP gear oil is almost the exact same thickness as straight 30W engine oil. The additives are different. 10-30 Mobil 1 is thicker with a cold engine than 0-30 Mobil 1 but the 0-30 is actually thicker than the 10-30 with a hot engine. If you need a thicker oil with your hot engine the 0-30 is better than the 10-30 Mobil 1.

I am using 5-20 Penzoil in my V12 Mercedes sedan and V12 SL coupe. I use it in my Expedition as well. When I get to 1,000 miles on the 575 M I will change the oil to a thinner one and work my way down. I used 5-20 in my 550 Maranello around town. By the oil pressures I could have gone thinner yet. The recommended 5-40 for that car was only good for high speed racing in summer heat at Orlando Florida. Otherwise it was way too thick, increased engine wear, decreased power and gas mileage.

All Mobil 1 oil viscosities are lower than other brands with the same rating such as 10W-30. The oil is thinner and I think this contributes to the engine longevity they are claiming. Also, a thinner oil will make starting easier, the starter motor works less, lasts longer. Same for the battery. The lower temp under the hood increases the life of rubber and plastic parts. The list goes on.

Mr Willis said that the shear ratings were higher for synthetic lubes. I cannot find any data to support this. The high temperature shear ratings for Penzoil mineral oi 5W30 is 3.1 and the Synthetic Penzoil 5W-30 is 3.05. For Castol the numbers are 3.1 for the GTX mineral and 2.92 for the full Syntec. These numbers indicate that mineral based oils have better shear protection than the synthetic.

The above is my opinion based on years of research and data collection, speaking with people at SAE and individual oil companies chemists to mention a few.

-Ali Haas


In reply:

Synthetic vs. Conventional Oils:
The most striking difference b/w synthetic oils and conventional or so called petroleum based oils is the homogeneity of the carbon molecule(s) or -using the jargon- alkane(s) lengths. Meaning the composition and effectivly the weight of the synthetic oil is an exact defenition of the molecular composition of that oil. So, when you buy 10W-30 oil, its been engineered to have a composition of alkane's that give the oil an exact cold viscocity of 10W oil, and an operating temp viscocity of 30W oil. In contrast to petroleum/conventional or "dino juice" based oil, the alkane lengths are variable and have a compostion more akin to a polydispersed [short chains mixed along w/ medium length chains and long chain alkanes], than the monodispersed synthetic oil.

So, the weight of the conventinal oil is more of an estimate than an exact measurement, this is what makes the conventional oil more succeptible to breakdown. Much akin to knock in a combustion cycle, when and organic molecule under extreme heat and pressure can form a radical [ an atom with one lone electron] species-very reactive and dangerous- this causes a chain reaction w/in the combustion chamber, breaking down the surrounding carbon molecules and propogarting the formation of more and more radicals eventually leading to spontaneous combustion or knock. This spontanous radical formation is also possible w/ engine oil, when exposed to high heat the possibility of radical formation increases, the radical species formed is capable of reacting w/ the metals and material w/in the motor, and the surrounding oil particles-accelarating their degridation and breakdown-leading to a chain reaction that leads to the breakdown of the oil. Which can, at the extreme, cause metal to metal contact, gasket degridation-as we know rubber and plastic harden and become brittle when exposed to high temp/burned then allowed to cool.

Synthetic oil, however, is less likely to succumb to such conditions largly b/c of its greater degree of molecular homogeneity, hence it is able to provide a more consistant barrier b/w the surfaces w/ in the metal against thermal abrasion. And, it itself is more stable hence protecting the internal surfaces-sorry for the redundancy-against radical(s) and the damage therin. One tangential point, synthetic oils b/c of their molecular composition, are somewhat "thinner" than their conventional counterparts, again b/c the alkanes w/ in the oil are engineered to given lengths, unlike the petroleum based oils which are blended together during/after the cracking of the natural stock takes place. That is why some people have complained of leaks when switching to synthtic on a motor w/ high mileage and a lifetime of petroleum based oil use. Rule of thumb, if you've been using petroleum based oil for the majority of the engines life, keep using petroleum based oils, just change the oil more often. Conversly, there should be no ill side effects in going the opposite direction, meaning synthetic to pertroleum based, so go ahead. Keep in mind, however, that going back to synthetic may cause a problem, if you decide to go back.

-Hubert Otlik
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Old 05-13-03, 08:09 AM
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The last misconception I will tell you about is that those oil viscosity numbers on that oil can are not what you think at all. For example, Penzoil 100W EP gear oil is almost the exact same thickness as straight 30W engine oil. The additives are different. 10-30 Mobil 1 is thicker with a cold engine than 0-30 Mobil 1 but the 0-30 is actually thicker than the 10-30 with a hot engine. If you need a thicker oil with your hot engine the 0-30 is better than the 10-30 Mobil 1.
hmmmm...now that is interesting!??? Damon what do you run when you are racing??? I was thinking about putting in 0-30
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Old 05-13-03, 08:31 AM
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I run Castrol 10w-30 dino oil and change it every 3000 miles or every two race events; whichever comes first. The reason I change it so often is due to the rotary's ability to get fuel in the oil and dillute it. If I had a boinger I would change at 5K and have no worries whatsoever.
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Old 05-13-03, 09:57 AM
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I'm not so sure I agree with Mr. Haas on his argument for thinner oils. A thinner oil with have a lower heat of adsorption; and thus will heat up faster and eventually decrease viscosity over time. Ferrari's new 575 Maranello manual confirms my assumptions with their different recommended uses for track and street duty. Thicker, higher viscosity oils will have better resistance to temperature breakdown; thus better suited for racing. Sure, for the average schmoe who doesn't take his car anywhere near "real" competition, there's no point to running thicker oil, but to advocate running thinner oil to reduce engine oil temps ..... no freakin' way. This guy needs a lesson in thermodynamics or, at the very least, heat transfer and kinematics. Internal fluid friction does NOT increase or decrease the temperature nearly as much as energy applied to the fluid.

Now to spin it on our viewpoint, FD's run HOT. Running thinner oils in a 13B-REW would be a mistake, IMO.
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Old 05-13-03, 01:34 PM
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oil requirements for for street cars verses performance and race cars are quite different. modern engines have been using thinner and thinner oil over the years. most car amnufacturers no recomend 5-30 or thinner oil for all their engines. parts are machined to higher tolerances and economy is a premium. for my street car I follow manufacturers recommendations. for my race car I run the thinnest oil that I can safely run. here in california I run 5-30 or 0-30 mobil 1 for races where the ambiant temp will be lower than 85*F. I run 15-50 mobil 1 on weekends where the ambiant temp is 85*F or higher. the thinner oil is what I would preffer but during the hot summer days I feel more comfortable with the thicker oil, but the engine will run the same oil and water temps with either. the thinner oil runs slightly lower oil pressure(maybe 5psi), but warms up easier. and the engine seems to use less of the thinner oil during the weekend. my engine also has larger clearqances on bearings to give more oil flow so the thicker oil should be better but the thinner seems to work the best. as always in racing experiment with different setups and always look for new ideas.
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Old 05-13-03, 03:35 PM
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Tims, with the thinner oil have you noticed any change in your oil temps?
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Old 05-14-03, 11:07 AM
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no oil temps are about the same 180-190*F during cooler temps and 200-210*F during heat of summer with either oil.
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Old 10-15-04, 10:30 PM
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Interesting read. Thought I would bump it for some of the new guys to check out.

Another reason not to go with overly thin oil for a modified FD is b/c of pronounced hearing wear with insufficient lubrication.
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Old 10-16-04, 12:16 AM
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All I have to say about the synthetic vs dino juice debate is I was using Valvoline 20-50 in FD, with exhaust, intake, and radiator. I could not have a consistant oil pressure due to the heat during the day. Especially if I drove it down. The heat would thin the oil to much i guess. Anyways I switched to Redline 10-30, and my goodness what a difference. I can run as hard as i want during the day and only see a 10lb drop from 40 to 30. And at night a consistant 50 to 60. I swear by it now.
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Old 10-16-04, 07:45 AM
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Originally Posted by Fatman0203
All I have to say about the synthetic vs dino juice debate is I was using Valvoline 20-50 in FD, with exhaust, intake, and radiator. I could not have a consistant oil pressure due to the heat during the day. Especially if I drove it down. The heat would thin the oil to much i guess. Anyways I switched to Redline 10-30, and my goodness what a difference. I can run as hard as i want during the day and only see a 10lb drop from 40 to 30. And at night a consistant 50 to 60. I swear by it now.

Fatman were you running VR1 or the all climate 20/50?

Thanks for the bump. Rich. I'm running the Amsoil 0-30 in my tow vehicle. I posted a long disertation (in the South forum) on my experiences with synthetic lubricants that I guess is long gone. Except for the huge issue of fuel dillution as Damon mentioned for the FD, IMO synthetics are the way to go. That said I run Valvoline VR-1 in my FD.
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Old 10-16-04, 09:42 AM
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I'm sticking with Racing Beat on this one.


"The Mazda factory does not recommend the use of synthetic oils in their rotary engines - specifically addressing this issue in the Owner's Manual.

In 1979, Racing Beat began testing synthetic lubrication products. Without a doubt, the best synthetic oils do perform well in extreme heat (over 300 F) and extreme cold (below 32 F), but by the nature of Mazda's rotary engine, the oil temperature never exceeds 250 F without severe engine damage due to other factors. In Souther California, we have difficulty seeing the low-temperature benefits: however, when we put synthetic lubricants in the engine, transmission, and differential in our IMSA GTU race car, we immediately saw what we later found to be a common result: The oil temperature in all three locations dropped 5 to 10 F for the same operating conditions. This is apparently due to two factors: reduced friction between sliding surfaces, and reduced foaming. As we continued to use synthetic oil products it became clear that they genuinely reduced wear. We also found benefits in street use. On two occassions, cars with "scratchy" transmissions synchronizers were completely cured by a change to synthetic gear lube. After many years of experience with these products we have observed only one problem: because of the reduced friction, the time necessary to break in an engine, transmission, or limted slip differential (standard differentials are no problem) is excessively long, so we recommend using mineral oil in all three for a time to ensure rapid break in."
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Old 10-16-04, 01:07 PM
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Originally Posted by cpa7man
Fatman were you running VR1 or the all climate 20/50?

Thanks for the bump. Rich. I'm running the Amsoil 0-30 in my tow vehicle. I posted a long disertation (in the South forum) on my experiences with synthetic lubricants that I guess is long gone. Except for the huge issue of fuel dillution as Damon mentioned for the FD, IMO synthetics are the way to go. That said I run Valvoline VR-1 in my FD.
Umm I was running the 20/50 that they say is for "performance" engines. See my problem with the dyno juice was it wasnt holding up to the heat consistantly. After a month , I guess to many hot and colds and it probably turned to thin. If you live in a HOT climate I would defintly recommend a synthetic. Im currently using 10-30 redline.
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Old 10-16-04, 03:17 PM
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I'll agree that a lower temps the oil pressure being higher when cold is a problem. That is why you warm up the car to temp. I don't think on a turbo application anything lower than 10-40 should be used. In less than 15 minutes it turns it to water anyway. That any my bearings in my turbo are getting used, and I get a little bit of smoke with thinner oil (5-30). None with 10-40
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Old 10-16-04, 04:42 PM
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While I'm certainly no expert, I use a sythetic 5W50 so that it gets good lubrication at startup (thickens as the engine warms up) and can operate with proper viscosity when warmed up. Thoughts?
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