Need Help with the basics please

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Jan 18, 2004
Phoenix, Arizona
I am do not understand a lot of the jargan I hear on this board and don't understand what a lot of the ratings mean, like the API ratings like CI-4, CH-4/SL, ILSAC GF-3 classification SL, and grade II, III, III or group II, III, IV etc. Can someone tell me how I can learn some of this basic information? It seems that the more I research oil the more I get confused. Please help. Tim C
I'm a rank amateur, but here's an (oversimplified) back of the envelope summary: The API ratings beginning with an "S" like SJ and SL refer to ratings approved for new US-market cars with gasoline. BTW, "SL" is the most current of these. API ratings beginning with "C" like CI-4 are ratings intended for US-market diesel engines. ILSAC ratings are oil ratings put out by the Japanese manufacturers. GF-3 is the most current of these, although GF-4 will become the most current very soon now. Oh, and you didn't ask, but the Euro carmakers have specs such as ACEA A1, A2 and A3 for gas engine vehicles. Also B1, B2, and B3 for light diesel engine vehicles. I think there's an ACEA "E" series for heavy diesel, but since I don't own any tractor trailers or farm tractors I don't follow that. The different groups, such as group 1, group 2, group 3, etc indicate degree of "syntheticness". Group IV and V oils are generally what EVERYONE will agree is synthetic. Group III is controversial. Some people (notably Castrol in the past) market Group III oils as synthetic, and that is highly controversial in some quarters. Group II is "highly refined" motor oil, but almost no one calls it synthetic. Group I is... less highly refined than anything else, and nearly as far as you can get from synthetic without just pouring crude oil in your crankcase. BTW, this is a beginner's view, and probably flat-out wrong in spots, but a good starting point.
For more info on ACEA, go here: and particularly which contains the actual specs for the ACEA standards. The general API web site is For API info, go here: For specifics about oil specs: Finally, I have no idea who defined Group I vs Group II vs Group V, etc, so I can't link you there.
Tim and any others that want to learn the basics: Bob wanted people to be educated about the basics because they would be better consumers and be able to discern in his opinion how much higher quality Schaeffers products were than many off the shelf lubricants and high cost "synthetics". He truly believes that a quality product will hold up to criticism if all are on the same sheet of music knowledge wise. Go to Bobs home page and take a long afternoon of reading. Also the intersting articles area has a GOLD mine of data that Molakule and others have contributed. Use the search mode to scan for words and descriptions that you don't understand. We each need to take responsibility for our own learning so we can contribute qualitatively to the site. Happy lube learning.
Tim, I would really love to explain basics for you as well as other board members. However, it will take too much space and opinions to describe even basics. I have a proposal to moderators and administrators of this board: Please make some kind of separate page with basic explanations and terms related to oil. That page probably has to be updated only once every couple months - doesn’t seem like a lot of maintenance work. I think that it would really help new board members to clarify and get acquainted with oil basics, terms, and technology. We all see here new members asking questions like: What's SL rated oil? What are 30 weights? What does 10W mean? What is a group II/III oil? Also abbreviations and their translation used on this board like GC, WOT, and etc. will be very helpful. Administrators and Moderators I suggest you start a new thread and members can give suggestions what information to include. Thank you,
Good synopsis, TomJones76! I would only add that Group I is essentially refined oil from the fractional distillation collumn that's undergone solvent de-waxing by adding solvent and chilling the mix to below freezing. It's then passed through filtration to catch most of the solidified wax crystals. After filtering the oil/solvent mix is heated to recover the solvent for re-use. Group II is an oil that's undergone high pressure and heat "isomerization" in the presence of hydrogen and a catalyst to "remove" the wax. "Removal" in this case is conversion of the wax molecules to desirable lube molecules, and while not a synthetic lube, the process does emply a form of synthesis to achieve its end. (Hence the logo "ISO-SYN" which Chevron displays on Chevron Supreme bottles). Group III uses a variation of the Group II technique with higher heat and pressure to further purify and raise the inherent viscosity index - "mo' better"... These oils are quite close to the performance of Group IV oils in most applications. Unfortunately, though the Group III base lube stocks only cost about half as much to produce as Group IV base lube stocks, the finished lube oils available to consumers are typically priced uncomfortably close to that of Group IV finished oils. Hence the rancor against Castrol U.S. production Syntec products on this board. Classic supply and demand - "He 'dat got 'da supply, can make 'de demand."
Tim whatever you decide on and read about, just remember not to fall for the "Hype". Oil is important, but it will not make the difference many of us on here suggest. Dino oil with poor numbers changed every 3k miles on your average car is fine for long engine life. It's good to match the engine/conditions to the right oil. As Sean Hannity would say: "Let not your heart be troubled." [Big Grin]
Even the Mobil 1 web site proclaims "if your driving is mostly on the highway and you change your oil religiously on the manufacturer's schedule every time, you may not need Mobil 1." Ultimately, it's up to you. Doug
Thank You everyone for your very informative responses and for the referenced links. It is great to be able to tap into such a knowledgeable group here. I have read the references and am still on a quest to learn more. I have a couple of questions from the board members. 1. How can we find out what group a particular brand/type oil is? 2. With regards to a synthetic blend how would we find out the group of the mineral base stock that was blended with the synthetic oil? 3. Does the manufacturer state the type of base stock they use (i.e. PAO) for a synthetic oil? 4. What group would a API CI-4/CH-4 oil be in? 5. I am getting the idea that in many cases you can’t really learn much about an oil by the API rating. 6. I am getting the idea that the CI-4/CH-4 oils are pretty much a premium quality mineral oil not just for diesel but for PCMO also, am I wrong? I have included an excerpt from one of the links that I read last night as I thought this might be interesting for others to read. Group I - Solvent Freezing: Group 1 base oils are the least refined of all the groups. They are usually a mix of different hydrocarbon chains with little or no uniformity. While some automotive oils on the market use Group I stocks, they are generally used in less demanding applications. Group II - Hydro processing and Refining: Group II base oils are common in mineral based motor oils currently available on the market. They have fair to good performance in lubricating properties such as volatility, oxidative stability and flash/fire points. They have only fair performance in areas such as pour point, cold crank viscosity and extreme pressure wear. Group – III Hydro processing and Refining: Group III base oils are subjected to the highest level of mineral oil refining of the base oil groups. Although they are not chemically engineered, they offer good performance in a wide range of attributes as well as good molecular uniformity and stability. They are commonly mixed with additives and marketed as synthetic or semi-synthetic products. Group III base oils have become more common in America in the last decade. Group IV -Chemical Reactions: Group IV base oils are chemically engineered synthetic base stocks. Polyalphaolefins (PAO's) are a common example of a synthetic base stock. Synthetics, when combined with additives, offer excellent performance over a wide range of lubricating properties. They have very stable chemical compositions and highly uniform molecular chains. Group IV base oils are becoming more common in synthetic and synthetic-blend products for automotive and industrial applications. Group V - As Indicated: Group V base oils are used primarily in the creation of oil additives. Esters and polyolesters are both common Group V base oils used in the formulation of oil additives. Group V oils are generally not used as base oils themselves, but add beneficial properties to other base oils. Note that the additives referred to in the Group V description are not aftermarket type oil additives. The additives referred to are used in the chemical engineering and blending of motor oils and other lubricating oils by the specific oil company that produces the finished product. Tim C
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