Group II, III, or IV

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There are lots of threads here where we discuss the benefits and pitfalls between group II, group III, and group IV based engine oils. Yesterday I came across a SAE paper (2001-01-1968) on diesel engine oils that concludes: “Extended oil drains in 1995 Caterpillar 3406 and 1996 Detroit Diesel Series 60 engines found no statistical difference in fuel economy or wear between a synthetic SAE 5w40 and an SAE 15w40 using A.P.I. Group II base stocks……” “Another study using 1999 Cummins N-14 engines found no statistical difference in fuel economy between a leading commercial synthetic SAE 5w40 and a leading SAE 15w40 using A.P.I. Group II base stocks plus a premium additive system…….” “Based on used oil analysis from the 1999 Cummins N-14 field tests, a leading commercial synthetic SAE 5w40 had statistically higher wear than a leading SAE 15w40 using A.P.I. Group II base stock plus a premium additive system. Both had the same A.P.I. CH-4-SJ/CES 20076/Mack EO-M Plus quality level.” The synthetic is a mix of 74.6% PAO, 0.4% Ester, and 25% Alkylated Naphthalene. It continues with 14 pages of graphs and details. A few days ago I would have told people I thought Synthetic was better, but maybe not worth the price in many cases. So could the difference be in our minds?
 
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so synthetics only advantage is in cold and very hot ? I never noticed better gas mileage. The truth is out there soon we will discover it. [ May 31, 2003, 04:15 PM: Message edited by: Steve S ]
 
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You really can not draw a direct correlation between large turbo diesels and privately owned non-comerical gas powered cars and trucks. The design of a large diesl is so darasticly different. The pistones are 2 piece designs with steel top and sides encased in an aluminum piston shell/skirt. THe clearance are much looser then gasoline engines and the parts are desinged with sever service and high loading in mind. They use piston oilers to directly lube the bottom of the piston and some inject oil into the cylinder as well. All of the bearing journals are massive in width. THey run at low rpms. They have have sumps that hold 20,30,40 gallons of oil. Most use bypass filter systems on every system including coolant. The vechiles seldom ar shut off for anything other then droping load, maintence, and fueling. I fully understand your point and it is a valid one. I have heard and read simalar studies. I just wanted to point out that these studies on diesel fleets rarely match non-fleet private use driveing styles. I gues we have to take our research where ever we can find it though!! Thanks for posting it!!!
 
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JohnBrown What do you mean by the clearances are looser in commercial engines? I had always thought diesel engines had very tight piston ring clearances to produce the compression needed to ignite. I have near zero experience rebuilding gas or diesel engines I'm just curious.
 
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A diesel's high compression ratio is achieved by the long stroke and the small space in the head at the top of the stroke. The rings do need to be a normally tight seal. I'm not sure that a diesel engine has much larger bearing clearances than a gasoline engine...somewhat larger so SAE 40 oil is appropriate, but that's all. The oil jet under the piston is for cooling the piston crown. One maker of very large engines (Sulzer) has water cooled pistons! You have to get into quite large diesels before you find oil injection into the cylinder walls. Some diesels do have large oil sump capacity. One I worked on (and in) held 30 tons of SAE 30 crankcase oil at normal level. That one did have cylinder oil injection...SAE 60 cylinder oil. I feel that synthetic oil's main advantages are cold weather operation and extended drain intervals. Dino oil with superior base oils and superior additive package will yield wear as low as any. Syn oil, and certain syn blends, will yield lower fuel consumption, although most drivers won't see a 3-5% improvement. Ken
 
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John Browning, the diesel engines referred in the above studys are the more common diesels used in semi type trucks . They have 1 piece pistons, there clearances are close to what we are used to seeing in larger auto engines . They have on average 12 to 15 gallon oil capacities . The 2 cycle detroit diesels had 2 piece pistons. Depending on the application they may run coast to coast team operation . Around town pickup an delivery "severe duty" or anything between. the big diesel engines have been through changes as gasoline engines for emission and feul consumption that you would understand.
 
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I dont know who started the rumor that modern diesels have sloppy tolerances. Nothing could be farther from the truth. If the did they would literaly rattle themselves apart.
 
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While some oil companies are more honest and market the 5W-40 product primarily for arctic weather, others try to claim fuel economy increases to justify the ~3x greater cost of the synthetic product. This claim appears to be false. These are not stationary, marine or locomotive engines, so I think this information does have meaning to owners of light duty diesels.
 
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These studies are in line with the mid-90's Consumer Report taxi test which found no advantages to synthetic, less than 5000 mile oil changes or brands of oil. Of course taxies are run almost continually and don't go through start cycles like the typical car. I stand by my contention that automobiles are complex systems and that things other than engine failure are generally going to take an automobile down. My daughter's 1993 Mercury Topaz just crapped out. New tires, a bad wheel bearing, bad tie rod ends and a failing alternator means scrap-gift it to charity. $1500 of repairs to an $800 car, and nothing engine related. Almost every car that I owned that bit the big one suffered a similar fate. Engine failure was a minor but contributing factor in only two or three over a forty year period-- two overheated and one suffered from the infamous Mitsu valve guide problem at the same time the transmission gave out. The rest died a more complex death with no engine problems whatsoever.
 

Jim

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I am not convinced that the wear rate is much less with synthetics but I know for sure that my car starts when it’s really cold using synthetics. Not many taxi cabs need to do that. I don’t know of very many taxi cabs that are turbo charged. But you are correct in saying that engine life is not normally a problem with cars these days. There is however a shop in town that does a very good business rebuilding engines. The cars are most likely from people that never change their oil.
 
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quote:
Originally posted by Jim: I am not convinced that the wear rate is much less with synthetics But you are correct in saying that engine life is not normally a problem with cars these days. There is however a shop in town that does a very good business rebuilding engines. The cars are most likely from people that never change their oil.
I agree with ya Jim. [ June 04, 2003, 02:26 PM: Message edited by: BOBISTHEOILGUY ]
 
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Bob-Tog: I was reading through the above thread and wondered at which point you were going to jump in. I bet you were watching to see how the forum played out first. I think that the advantage of synthetics is their possible longer service life due to their resistance to oxidation. That would include H saturated HCs or group IIIs. Some synthetics have an additive solubility problem, so the notion of a longer lubricant or fluid life cannot be a blanket statment. Most agree that synthetics (including group IIIs) flow better at extreme cold temperatures, so then in a moderate climate synthetics would not be of an advantage over a product manufactured from a conventional base stock. Most agree that in the event that the lubricant is subject to extreme heat the synthetics are superior to conventional base lube products, but if the lubricant or fluid is not subject to those high temperatures, then synthetics may offer no advantage. Some people hold dear the notion that synthetic fluids and engine oils lubricate better because they believe that synthetics have a stronger film strength and provide a better oil wedge. Yet in applications where a lubricant is not subject to temperature extremes, or cold start cycles, synthetics do not improve fuel efficiency or provide a longer engine life. So in conclusion to a discussion that started on another board.....YES!!! Your conventional lubricant is better than my synthetic, or do I have that backwards??? [Smile]
 
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Neil in reguards to clearances I was mostly refereing to main bering clearances.I am not sugesting that diesels are built slopy!! I am sugesting that the clearances are not as tight as you would find in a Nissian Maxima V6, Audi turbo 4 or any number of modern gassers. I am also suggesting that an oil that will survive for 20,000 miles in a N14 would not last 7500 miles in a Toyota Siena or a Saturn. It is common place for a commercial diesel to hit 1,000,000 miles with out major overhaul while this is still incrediable rare in non-commerical privately owned vechiles. Their is absoulutely no reason why a gasoline powered engine could not built to last this long other then price and C.A.F.E.. The engine would be so much heavier that it would be difficult to meet C.A.F.E. and the engine cost would double! The design spec.s and even the operateing cycle in most respects is so totaly different that the research is only valid to diesels. I do not even have an issue with the results in most respects I would agree. It would be like someone doeing research on a monkey and then proclaiming that it would also be the same on humans. We all know that seldom is the corelation from monkey to human even close! [Off Topic!] [Big Grin] I would love to see some large scale studies on additive packages and premium conventional base stocks on daily drivers! It seems to me that the only way to get an oil with a beefy additive package is to buy synthetic. Schaffers is the only conventional oil manufacture that I am aware of that really puts a good additive system in their oil. Most of the conventional oils that you can buy off the shelf have really anemic additive packages. It also bothers me that in order to get good group III conventional oil you have to buy mislabled oil at double the price it should sell for! I have always thought that oil should be like OTC drugs. They should have to list the exact ingredients and amounts on the back label. Companys do so much double talk these days that I only trust Mobile,Redline and Schaffers. By trust I mean that the product is properly labeled as to it contentents(synthetic,blend,non-synthetic) and that they take pride in makeing a great product at resonable prices. [Big Grin] [Big Grin]
 
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It's no surprise at all that 5W-40 and 15W-40 oils give the same mileage in OTR trucks run all day long at normal operating temperature. The only factor affecting economy under those conditions is the HT/HS viscosity, which is likely very similar for both 40 weights. In a truck used for short daily commutes where engine warmup is a factor, it is likely that the 5W synthetic would show the advertised small increase in economy.
 
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Drstressor; That is exactly what I have been reading in all of the truckin' magizine articles. The "synthetic" 5W40s are said to give about a 3% fuel savings in short trip applications, and when cold start cycles are a factor. As far as the extended drain intervials are concerned with synthetic use? I think the evidence of those come mostly from testimonials at the present time.
 
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HI Here is my experiance with synthetic oils. I have a 2001 psd and my brother has a 1999 psd. WE went to Colorado snowmobiling, we did not start our trucks for the week we were there. It just happened to be in the middle of a cold spell -30 nights 0 days. When it was time to leave we noticed all the trucks (all brands) were plugged in and hoods opened. Both of our trucks started with "NO Problem" boy did we get looks,sinse ours were not plugged in. The next summer I put Full synthetic in my commercial "Air cooled" lawn equipment, on every piece of equipment the operating temperture dropped at least 10 Degrees or more. I will stay with my Full Synthetic Oils,Rotella and Mobile Just my Experiance citro
 
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Not having the study to analyze, I cannot say whether I believe it to be valid or not. If the study just compared a short run over a controlled stretch of highway with new synthetic and group II oil then I would conclude the study as invalid. Should the study have taken place over the course of one complete oil service interval (10,000 or 20,000) miles then I would tend to conclude it had some validity. I was wondering if anyone would like to do a study with their own vehicle to determine if they get better mileage with synthetic versus dino. The survey should compare two oils with similar viscosities. Say two 5w30 oils with a viscocity of 11.7 (a thick 5w30 Amsoil) or two thin 30w's like Mobil 1 5w30 versus a similarly thick dino. Any takers?
 
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quote:
I stand by my contention that automobiles are complex systems and that things other than engine failure are generally going to take an automobile down.
I agree. My '82 GMC 6.2L diesel pickup with 227,000 miles on the original motor died in an engine electrical fire. *sniff*... RIP [Frown]
 
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