Go BottomSynthetic Oil and Holding Capacity
 | Peters
Join Date: Feb 2002 Posts: 3034 Northern AL 
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2003-07-04 58835
We have had a number of discussions on synthetic oil and its superior lubrication. A few members stated that they had repaired gas engines that were using synthetic and there was a marked difference in the wear in the engine.
I have seen as have others that the oil stays cleaner than conventional oil. Members have seen the oil clean at the change interval with newer diesel engines. We assume this is primarily due to less breakdown of the oil, but the other source for contaminates, combustion is marketly more dirty than with gas.
Has anyone here broken down a diesel engine running with synthetic? I guess I am concerned that the synthetic may have less particle holding capacity do to the fact that the base stock is highly hydrophobic. Ie the oil may be clean but the oil journals maybe dirty. I would assume that they use a better surfactant to help keep the particles in suspension but you don't know unless you rip one appart. I am not inclined to rip appart my new engine.
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 | kwschumm
Join Date: Feb 2003 Posts: 5764 NW Oregon
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2003-07-04 58854
This experience doesn't directly reflect on diesel engines but I'll recount it anyway. When I was 18 I bought a new VW Scirocco. After break-in I used nothing but SL-1 (don't know if they're still around) and Amsoil synthetic oils and changed it every 5000 miles. At 100,000 miles I added a turbocharger to the car and drove it around for another 20k miles. Wanting more power I adjusted the wastegate to gain more boost - and promptly blew the head gasket. When I pulled the heads I couldn't believe how clean the engine was. No carmelization and no sludge at all. I could still see the machine marks on the cam at 120k miles! This experience sold me on synthetics for good.
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 | Misenplace
Join Date: Jul 2003 Posts: 875 Michigan 
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2003-07-04 58868
I have a 95 Bronco with a 351C. I use mobil 1 and have since it was fairly new. At 100,000 miles I still change the oil every 5k miles. There is no loss of oil even at this age. I strongly believe in synthetic oil for the engine. ....
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 | TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2003-07-05 58877
My impression is that detergent petro oils have additives in them to disperse water and that engine heat evapourates it. If that's true then base petro oils also are pretty 'hydrophobic' and maybe synthetics also have an additive. I've heard that detergent oils shouldn't be used to lubricate electric motor bearings because the oil holds water in suspension and can corrode parts. Electric motor bearings don't get hot enough to evaporate water.
It does seem like a good question. You were probably thinking about your truck but if used oil from a tractor using a synthetic looks cleaner compared to petro oils after similar use, where does the soot go? My used oil (which NH describes as a semi-synthetic) is black and 'gunky' in less than 100-hours. I imagine that operation keeps deposits mostly scrubbed off moving parts but I remember gas engines 'inereds' used to be coated with a light gray cream here and there. Well, this was back in the days when most gas engines had run most of their lives on leaded gas and I heard that the cream contained lead residue from the gas. I don't know what deposits on newer engines looks like--gas or diesel.
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 | Art White
Join Date: Jan 2000 Posts: 6898 Waterville New York
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2003-07-05 58883
We have not seen much in the ag industry in synthetic oils. I think that it might be to small of an area for them to cover for the dollars needed to bring a product to the market. For some of you it might be interesting that we often run our trucks, even gas engine several hundred thousand miles. The last one I rode that far at 150,000 had to put valve cover gaskets on and it was like new under them with 4000 mile oil changes. Got rid of it at 200,000, for me it was using a quart every oil change, I do drive a little fast,the new owner informed me it didn't use any as he was using it between NY and Georgia but just driving 55. He did tell me it does have difficulty making it past two consecutive gas stations! Truck still going this spring just past 255,000. ....
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 | DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada
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2003-07-05 58894
Pennsoil has a GMC truck on their web site with a documented 1,000,000 miles on it. ....
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| Peters
Join Date: Feb 2002 Posts: 3034 Northern AL
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2003-07-06 58957
Tom; the detergent in oils emmusifies water but it is not added to oil for that but to increase the holding capacity of the oil. To increase the ability of the oil to suspend dirt. One of the biggest differences between a diesel certified oil "C" and a gas engin oil "F" is the detergent package.
Water absorbed into the oil is one reason that it is good to have the engine fully heated before it is shut off. In cool damp climates (or boats) you can see the oil froth at the breather etc. You need to drive the water that has condensated out of the system.
You are right an electric motor should not use a detergent oil. They do not heat up enough to drive off the water vapor. I have made that mistake before. Any other equipment that does not heat up enough should also be the same way, air compressors, sewing machines etc.
Most of the older gas engines I rebuild were run with leaded gas. Maybe the sludge build up was due to the lead and not normal old age. I have rebuilt a few head since but they were not as old. Certainly they looked cleaner. Better oils and no lead certainly make a difference.
I guess the question then comes down to is the heavy dark soot in the used diesel oil, break down of the oil rather than combustion products? ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2003-07-07 59017
I guess my impression would be combustion products--carbon from incompletely burnt fuel. But come to think of it oil is mostly carbon too, so thoroughly broken down oil probably would be black as well. Don't know, may be some of each.
I don't know exactly how detergents in oil work. From an ancient recollection I think that end of detergent molecules attract water and the other oil, and I guess that action can emulsify oil in water or water in oil. I don't know if particle suspension works due to the ability of detergents to emulsify or due to some other action.
I guess that if synthetics do have less particle suspension ability than petro oils then detergents probably work differently with synthetic bases. It's an interesting subject but it's also just idle curiosity on my part.
Tests required for us to get the 500 gallons of used engine and hydraulic oil we bought along with our camp proved to have lead contamination. I guess that the former owner had been collecting it since the days of leaded fuel. I'd guess that the gunk in old engines has a pretty high lead content. Most newer engines I've been into were motorcycle engines and they were fairly gunk free and that may be due to better oil or more frequent changes. Leaded fuel was still around at the time and few riders wanted anything to do with unleaded gas.
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| Peters
Join Date: Feb 2002 Posts: 3034 Northern AL
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2003-07-07 59090
When you think of polymer material in general like attacts like material. Oils are oligomeric (small chain polymers) and therefore the same principle applies.
Synthetic oils are essentually short chain polyethylenes. Diesel and gas are complex mixtures of aromatics, unsaturated and saturated hydrocarbons. Naturally mineral oils are a mixture of aromatic and aliphatic oligomers.
Detergents are materials with hydrophobic and hydrophilic functions. They do not just emusify the oil but also suspend dirt particles in the oil. When you stop stirring the oil with out the detergent in the oil the dirt will drop out into your pan.
I recently helped a friend's son replace his oil pump on his truck. I was suprised at how clean the pan was despite having nearly 120,000 miles. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2003-07-08 59111
Thanks Peters. I know this is your subject. I've got a better handle on the idea now.
I did assume that particle suspension was a different action then emulsification. I was thinking that otherwise there'd probably have to be water in the oil for it to suspend particles, which didn't seem too likely.
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| PI
Join Date: Posts: 1 
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2003-07-08 59136
I strongly recommend synthetics to those serious about engine care. Check out the link here. Note spec's like pour point (for winter/cold engine wear), volatility weight loss for long change interval, film strength for metal to metal contact resistance. Use GOOD filters too. Its the particles in the oil being recirc'd through the engine that cause the wear. Amsoil (and others) offers oil analysis service which is worth trying if you've never done that. That'll tell you what's going on in your engine including particle sizes, etc. ....
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