First read: http://ferrarichat.com/forum/showthread.php?t=38205&page=1&pp=20 Motor Oil 102 Chapter two. It gets more difficult. We left off discussing that a 0W-30 weight oil is not thinner than a 10W-30 oil. They both have the same thickness at operating temperature. The 0W-30 simply does not get as thick on cooling as the 10W-30. Both are still way to thick to lubricate an engine at startup. I have heard several people say that Porsche specifically prohibits a 0W-XX engine oil, that it is too thin. Now here is the partial truth I spoke of earlier. We will discuss multi viscosity oils. Earlier we said that a straight 30 weight oil has a thickness of 10 at the normal operating temperature of your engine. The multi viscosity oils 0W-30 and 10W-30 also have a thickness of 10 at 212 F. The difference is at 75 F, your startup temperature in the morning. Oil type... Thickness at 75 F...Thickness at 212 F Straight 30...... 250......................10 10W-30............100......................10 0W-30..............40 ......................10 Straight 10........30....................... 6 Now you can see that the difference between the desired thickness your engine requires ( = 10 ) is closest to the 0W-30 oil at startup. It is still too thick for normal operation. But it does not have far to go before it warms up and thins to the correct viscosity. Remember that most engine wear occurs at startup when the oil is too thick to lubricate properly. It cannot flow and therefore cannot lubricate. Most of the thick oil at startup actually goes through the bypass valve back to the engine oil sump and not into your engine oil ways. This is especially true when you really step on that gas pedal. You really need more lubrication and you actually get less. Note that a straight 10 weight oil is also too thick for your engine at startup. It has a thickness of 30. Yet at operating temperatures it is too thin having a thickness of 6. It needs to be around 10. The oil companies have added viscosity index improvers or VI to oils to solve this dilemma. They take a mineral based oil and add VI improvers so that it does not thin as as much when it gets hotter. Now instead of only having a thickness of 6 when hot it has a thickness of 10, just as we need. The penalty is the startup thickness also goes up to 100. This is better than being up at 250 as a straight 30 weight oil though. Oil with a startup thickness of 100 that becomes the appropriate thickness of 10 when fully warmed up is called a 10W-30 weight motor oil. This is NOT as thick as a straight 30 weight oil at startup and it is NOT as thin as a straight 10 weight oil at full operating temperature. The downside of a mineral based multi-viscosity oil is that this VI additive wears out over time and you end up with the original straight 10 weight oil. It will go back to being too thin when hot. It will have a thickness of 6 instead of 10. This may be why Porsche (according to some people) does not want a 0W-30 but rather a 10W-30. If the VI wears out the 0W-30 will ultimately be thinner, a straight 0 weight oil. When the VI is used up in the 10W-30 oil it too is thinner. It goes back to a straight 10 weight oil. They are both still too thick at startup, both of them. The straight 0 weight oil, a 5 weight oil and a 10 weight oil are all too thick at startup. This is just theory however. With normal oil change intervals the VI improver will not wear out and so the problem does not really exist. In fact, oils do thin a little with use. This is partly from dilution with blow by gasoline and partly from VI improvers being used up. What is more interesting is that with further use motor oils actually thicken and this is much worse than the minimal thinning that may have occurred earlier. Synthetic oils are a whole different story. There is no VI improver added so there is nothing to wear out. The actual oil molecules never wear out. You could almost use the same oil forever. The problem is that there are other additives and they do get used up. I suppose if there was a good way to keep oil clean you could just add a can of additives every 6 months and just change the filter, never changing the oil. When the additives wear out in a synthetic oil it still has the same viscosity. It will not thin as a mineral oil. The fear that some say Porsche has that oils thin when the VI runs out is not applicable to these synthetic oils. These oils will always have the correct thickness when hot and will still be too thick at startup as with all oils of all types, regardless of the API / SAE viscosity rating. Automotive engine manufacturers know these principals of motor oils. They know there is thinning or thickening that will occur. They take these things into account when they write that owners manual. Mineral oil change recommendations will generally include shorter time intervals than those of synthetic oils. The reality is that motor oils do not need to be changed because they thin with use. It is the eventual thickening that limits the time you may keep oil in your engine. The limit is both time itself (with no motor use) and/or mileage use. End of part two. aehaas PS - Yesterday I spoke to a person at SAE about the new SM specification. We discussed many things but she got a big laugh when I told her that some people insist on using oils of an earlier specification because their old car manual said so. PPS - I would like to thank the folks at the Society of Automotive Engineers, Inc., SAE, and ASTM for providing free copies of the latest J300 specifications and D 4485 -03 Engine oil standards.
Several things mentioned in the previous section of Motor Oil 101 are so confusing that I have to correct them now. One person said that Formula 1 cars use 70 weight oil. This is incorrect. I have spoken with several oil companies and FNA and they will tell me that they cannot give me specific data on the oils as they are proprietary. They have no real rating. However, they do all tell me that the oils are on the order of being very thin as a 5 or 10 weight oil. Red Line does make 2W, 5W and 10W oils (this acts as a 0W-10 multigrade oil) but they are for racing only. At least one Formula 1 team has actually used these very oils off the shelf from Red Line. Quote: "There is no rocket science here. 5W-30W has a viscosity = to the 5w when it is cold and 30W when it is hot." This is why I say to ignore the numbers on the can. They refer to the "grade" of oil, not the viscosity. The average 5W-30 multigrade oil has a viscosity of 70 cS at 75 F startup . It has a viscosity of 10 cS at the normal operating temperature of 212 F. The statement is actually technically correct but confuses most people. This is why I go slow with information and try not to be too technical. Most people think that the numbers 5 and 30 refer to thickness or viscosity. They do not represent actual viscosity figures. They represent classes or grades that oils are put into. aehaas PS - From Motor Oil 101: Please forget those numbers on the oil can. They really should be letters as AW-M, BW-N or CW-P. The fact that we are dealing with a system of numbers on the can makes people think that they represent the viscosity of the oil inside the can. The problem is that the viscosity of oil varies with its temperature. A 30 weight oil has a viscosity of 3 at 302 F ( 150 C ) and thickens to 10 at 212 F ( 100 C ). It further thickens to a viscosity of 100 at 104 F ( 40 C ) and is too thick to measure at the freezing point of 32 F ( 0 C ).
I can tell you that my 996 has been serviced at the dealer all its life and they only put Mobile 1 0W40 oil. So it is not true!
I am compelled to comment on the following statements made in the 101 section: Pressure and flow are tied together with viscosity, but none have anything to do with lubrication. Lubrication is a property of the fluid, not the force. The oil pump would pump water just as well, but it would offer no real lubrication. If we double the pressure, we double the flow. If you decrease the viscosity to a lighter oil, you increase flow at a loss of pressure. High flow helps to carry away more heat. High pressure helps to keep metal parts like the bearings out of contact with each other (scuffing). High pressure increases flow, as well. Usually in building a street engine for racing, oil galleries are drilled out larger, to carry more oil, and the oil pump is at least doubled in size. I would just guess, that your basic Ferrari is probably flowing in the neighborhood of 2 to 3 or more quarts of oil per second at higher rpm, with over half of it flowing past the crank bearings. I give you the following example to help visualize what is really happening. This assumes the oil has no internal resistance. In actuality doubling the pressure will not double the flow but will be slightly less. And thicker oils have more resistance than thinner oils for all situations. But simplified we get the following: For a 30 wt oil at operating temperature: RPM....Pressure..Flow 1,000......20 PSI....1 2,000......40 PSI....2 4,000......80 PSI....4 8,000... 160 PSI....8 The maximum flow because of the oil pop off valve at 90 PSI will be 5 For a 30 wt oil at operating temperature and a higher output oil pump: RPM....Pressure..Flow 1,000......30 PSI....1.5 2,000......60 PSI....3 4,000....120 PSI....6 The maximum flow because of the oil pop off valve at 90 PSI will be 5 8,000... 240 PSI....12 If we stick with the same weight oil and increase the oil pump output we will increase the pressure and the oil flow too. If we double the oil pump output we will double the pressure and we will double the oil flow. For a 40 wt oil at operating temperature: The oil is thicker, has more internal resistance and therefore requires more pressure to get the same flow. RPM....Pressure..Flow 1,000......30 PSI....1 2,000......60 PSI....2 4,000....120 PSI....4 8,000....240 PSI....8 The maximum flow because of the oil pop off valve at 90 PSI will be 3 For a 40 wt oil at operating temperature and a higher output oil pump: RPM....Pressure..Flow 1,000......45 PSI....1.5 2,000......90 PSI....3 4,000....180 PSI....6 The maximum flow because of the oil pop off valve at 90 PSI will be 3 8,000... 360 PSI....12 For a 40 wt oil at operating temperature with the original pressures RPM....Pressure..Flow 1,000......20 PSI....0.5 2,000......40 PSI....1 4,000......80 PSI....2 The maximum flow because of the oil pop off valve at 90 PSI will be 3 8,000... 160 PSI....4 Increasing the pressure while using the same oil will increase the oil flow but increasing the pressure by increasing the oil thickness will result in less flow, a lot less. It takes more pressure to move a thicker oil. When you go to a thicker oil the pressure goes up because of the increased resistance, and therefore reduction of flow. Furthermore pressure does not equal lubrication. Let us look at a single closed lifetime lubricated bearing. We could hook up a system to pressurize the bearing. This can actually be done. We could have the oil at ambient pressure. We could then double, triple, quadruple the pressure of the oil. The oil is non-compressible. Regardless of the pressure we would have the exact same lubrication, that of the ambient pressure lubrication. The physics of lubrication as I said earlier show a 1:1 relationship of flow to separation pressure. Lubrication itself is pressure independent. I will not get into the equations for this board. Water is a good lubricant. This is partly because of its high surface tension. It is used in many medical devices and other systems that are under or exposed to water. It is just that water rusts metal parts making this unsuitable for automotive engines. It actually has a higher specific heat than oil. It can therefore carry away more heat than oil from bearing surfaces. In this respect water is a better lubricant than oil. aehaas
Sorry Ali about my words included in your original quote. I guess I don't know how to quote just a portion of your great thread. It looks like my previous reply looks as if it was your quote. Philip
Philip - Just make sure when you cut and paste a quote that you include the [/QUOTE] at the end of the quoted passage for proper formatting. Gary
It is easy to see why motor oil is an endless topic. For everything else, use MasterCard. When you change from that 30 to a 40 weight oil you can get the same flow with increased pressure. But there is a penalty. The maximum flow rate is lessened. This occurs with the higher heat and RPM situation when more flow is needed. To move that thicker oil you need to use up more BHP. This heats things up in your engine and robs HP for no good reason. You have the same flow and lubrication but under more stressful engine conditions. Higher heat = more wear and tear. I do not see the benefit here. aehaas
I have been following this thread and find the information outstanding. I like the idea of 5-30 or 0-30 for my 355 but knew just before I got the car in May that it had fresh oil change. Since I have put 4K on my car and was deciding on what to try, so today I checked the oil sticker reminder to see what was put in last. I now have a knot in my stomach, apparenty the former owner used Royal Purple sythetic oil with a viscosity of............15W50!!!!!!! Could this have actually done damage to my engine, I don't even want to start it up again!
Don't lose any sleep over it, and drive the car. I put nearly 100k miles on a Porsche some years ago using 15W-50, never any problems. Gary
Thank you so much for the time , energy,and info you contributed to Chat-- very interesting reading. While I think I get the drift of your writing that lighter viscosity oils are better due to flow characteristics, why do the Ferrari manuals call for such heavier oils. For example my car's manual ( '85 308) calls for 10w-50. I've been using Castrol 20w-50 or Mobil1 15w-50 in the summer months and 10w-40 in the Winter in that these are close to the rec'd wt. Do you know of any controlled studies which actually compare engine wear( via post-test tear-down) over time with various wt oils? It would appear that you believe that motors with the lighter oils would last longer--ie, experience less wear over time. I would think that most Ferrari owners follow the manual's recommendation, as I have, and these engines seem to hold up pretty well over time . It would be great to know, via real-life tests that the life of the engine could be extended even longer merely by installing a lighter oil.
Thanks for the great informative section.The relationship oil viscosity vs. BHP ( net power subtracted to the engine to drive the oil pump ) is confirmed and very evident in Europe .Here since progressive introduction of tighter regulations for tail pipe emissions ( CO2 ) and max allowed fuel consumption, a trend was established by all engine manufacturers toward longer oil change intervals and 10W-->5W-->0W grade oil simply to reduce costs and fuel consumption . Another advantage which ties up with Dr. Haas comments is that you actually may need a smaller starter to start your engine , even if at cold/freezing conditions, being the engine friction losses lower . For mass production volumes a relevant cost reduction source. The flip side of thinner oils ( sorry for this over-simplification ) is the need of a relevant redesign work of the entire "wear and tear " engine section ( so called power cell including piston and rings,pin, bushing,con-rod main bearing,piston cooling jets) and of the lubrication circuit to better cope with the changed conditions. Some car manufacturers who apparently were too aggressive toward premature introduction of thinner oils on mass vehicles ( think about taxi drivers, mom stop and go city driving) did encounter significant field problems because sint thinner oils may have different performance limits than old guard mineral oils at very specific conditions ( low oil pressure, higher oil temperature,semi-clogged oil tunnels, clogged oil filter---> so called marginal lubrication conditions ). Would thank Dr. Haas addressing and elaborating on this aspect during the next to come sections.
Changing your oil is unlikey to have a measurable effect on fuel consumption. Of one gallon of petrol burnt in an engine, 60 percent of the energy will be lost as heat from the exhaust and cooling system. That leaves 40 percent of which 25 percent is used to drive the car and its accessories. The remaining 15 percent goes to losses such as pumping air into the engine (6 percent) and 9 percent is lost as engine friction. Of that 9 percent, 6 percent is lost in churning the oil. These figures are from an AA report into Oil Additives. However, using the correct oil throughout the lifetime of the engine will mean it maintains it's efficiency for longer...so in the long term it can have an effect. If you stick to the manufacturer's recommendation (and it's synthetic), while there may indeed be better oils, you won't go far wrong.
Someone asked for my credentials, that I somehow dont know what I am talking about. First off, I am no doctor, I don't even play one at home. And to be honest, I hav'nt seen anyone elses and I don't feel like making phone calls to verify them. But, I have been turning wrenches since I was 8 years old. I have worked on virtually every single make of car most people can think of except a Rolls Royce or a Lamborghini. I have not worked on any eastern european cars, but they don't really count. On top of that I have worked on heavy equipment, and aircraft. If anyone thinks anything is more technical than aircraft, from any standpoint you can think of, tell me, I would love to hear about it. Aircraft fall under Federal guidelines and if you mess up, you lose your mechanics license. You need a license to work on aircraft. You need to read anything and everything dealing with any particular work you plan to do. And you need to understand oil. At least some. All oil poured into an aircraft engine, has to be FAA approved for use in that "particular" engine. Period. SAE stands for Society of Automotive Engineers. FAA and AN, and Mil spec, all pretty much follow suit with SAE, and all of these different engineering specifications can be cross referenced to each other. I refuse to argue about what SAE 10, 20, 30, 40, 50, or any other number someone wants to throw around, about what those numbers mean. They mean what they say they mean, period. If you cant understand SAE viscosity, then go read a paper on it, there are hundreds on the web, and many at the library. Every car, truck, lawnmower, airplane engine, locomotive, any engine in the world, no matter who made the thing, they all use SAE numbers. Period! Period! Period! Even your blessed Ferrari, Porsche, Lambo, what have you, they all use SAE numbers. My 308 has a decal on the right side engine compartment that uses SAE viscosity numbers. I didnt say what I said out of some half dead stupor, most of it I quoted from other sources, most of it from aviation material, as they tend to go deeper into technical details than any other conveyance. There are no technical papers dealing with viscosity indexes other than SAE indexes. I explained before, in somewhat limited details, how SAE calculates viscosity. If you have any arguments please take it up with the society. I stated I had "read" somewhere that "some" F1 racing teams had used SAE 70 motor oil in thier engines. I do not recall which teams or even when, but as I only trust and read magazines like the Star, R&T, Automobile, I believe what I read was correct at that time. Many aircraft used to run straight 70 oil, some still do, its not that uncommon, and i don't know about today but years back motorcycles like Harley used 70 weight. Ive seen engines so hot that 20W50 poured like water, and at those kind of temps I would imagine 70 wouldnt be much thicker either. I stated that a while back there was a problem with 10W40. This was well known and if you care to dig around you will find information on it, I'm not talking out of my ass. If Ferrari approves a new 15W40, well lets see, thats not 10W40. It also was probably more prevalent with CHEAP OIL! As far as viscosity breakdown in as little as 500 miles, yes, its well known to happen. WITH CHEAP CRAPPY OIL! The top brands certainly have bragging rights to make the claims that they do, and by the comparisons you can find on the web, or in other sources, they are trustworthy. Personally I like Castrol, their top oil is almost up the the high temperture cook off of Mobil 1. It just doesnt flow as good cold. To recap one last time. 30 weight oil is 30 weight oil is 30 weight oil. Its given that number by how it flows at a temp of 210 degees F. How it flows at 0 is irrelevant to its rating. a 10W30, is still a 30 weight oil. Its base stock is 30 weight oil, determined at the same 210 degees F. The only reason it has a stupid 10 attached to it is because they added things to the 30 weight oil to make it "act like" a 10 weight oil at 0 degrees F. These are not my foolish ramblings, this is the exact explanation by the SAE. the "W" means simply, WINTER. Does 10 flow very good at 0 F? No. Is it thick? Is it thicker than at 210 F? I just get tired of people trying to say what something means, when they obviously havnt taken the time to study the issue or try and understand something. If we all start going off on tangents trying to change empirical numbers, everyone will be so confused they wont know what to do. SAE is the numbers on your oil can. I doubt anything will change in another 100 years. Would you like if people started changing how we read blood pressure because they dont understand millibars of mercury? Should we have 20 different types of blood pressure results all over the country so no one understands it anymore? Should we have another standard for air pressure? PSI and kilopascals to complex? Maybe 40 bull balls per circular tortilla? 3 Lefse per brod? You dont change the way something is arrived at just because you don't understand it, you learn how to read it and understand it. If I have a tube, a certain size, and I heat it in a water bath to 210 degrees, and I pour a liter of a some fluid, also heated to 210, through the tube, and it passes through in so many seconds, and I read a chart that tells me what viscosity a fluid is, that will flow in that time, at that temp, through that certain sized tube, .....and, if everyone in the world doing testing uses the same size tube, and the same type equipment, and the same volume, and the same charts, I would imagine we would all have simular results. If what I just wrote doesnt make sence, then there is no further need of discussion
SAE Viscosity Grade The center of the Donut shows the oil's SAE viscosity grade. Viscosity is a measure of an oil's flow characteristics, or thickness, at certain temperatures. The low-temperature viscosity (the first number, 5W in a 5W-30 oil) indicates how quickly an engine will crank in winter and how well the oil will flow to lubricate critical engine parts at low temperatures. The lower the number the more easily the engine will start in cold weather. The high-temperature viscosity (the second number, 30 in a 5W-30 oil) provides thickness, or body, for good lubrication at operating temperatures. A multigrade oil (for example, SAE 5W-30) provides good flow capability for cold weather but still retains thickness for high-temperature lubrication. A single grade oil (a single number in the center of the donut) is recommended for use under a much narrower set of temperature conditions than multigrade oils. Operators should refer to their owner's manuals to select the proper viscosity oil for the ambient temperature and operating conditions at which the equipment will be used.
Not to be a jerk, but you do realize that none of these professions (or hobbies as I believe one is) brings with it any knowledge of hydrodynamic bearing design, right? I'm far from some engineer snob; I'm the first to admit that mechanics can teach me a lot about how cars work, but being a self-described (credentialed or not) "mechanic" as either Ali or Paul have stated doesn't mean that one knows how to design a bearing. Just about everyone that turns a wrench for a living or under a shade tree gripes about those stupid engineers in Detroit, how could they do it like that... But unless you're upstream in the product creation process, you really don't have a clue about why something may be the way it is. I've been on both sides. But I digress. Now it seems that Ali has made this his hobby, so I'm listening very intently to this interesting discourse which has already prompted me to pull out a textbook to get a little input of my own! As this topic further evolves I'll be following closely and running the statements through the understanding I'm getting from published texts; you never know, I could even ask someone that's ACTUALLY DESIGNED a journal bearing and put millions on the road! In the meantime, I'm all for the discussion, and I expect to ask some of my own questions next week or so, but in the meantime, let's go ahead and keep "credentials" in perspective, ok?
Don, I think all of us with a little grey in our hair (okay maybe a lot of grey) have gotten to the point in life that credentials, in and of themselves, are not the key factor we use to evaluate the credibility of information we read, particularly on the Internet. In fact, the older I get, the more suspicious I get of all so-called experts. (Witness the last election as one example.) For example, I have a Ph.D. in business. But I couldn't even begin to tell you the number of Ph.Ds, in all fields, that I have met who couldn't be trusted with a sharp object in their hand. However, it is apparent from even a cursory review that Ali has a passion for facts. Personally, I find this refreshing because so many of us have gotten so dogmatic in our views that we don't wish to be brothered by facts. Take F1 shifters, for example. There are many of us who automatically trash F1 clutches because we want a "real car." So keep bringing it on, Dr. Haas. I might even learn something! Dale
I am certainly not the master. I do like metal work however and have made low tech bearings just to do the project. A look into my garage shows a lathe, vertical mill and not shown several types of welders. What is really interesting to me is that I have spoken with probably 50 people who are involved with automotive engine oil development. This just in the last year. What I find most interesting is that most of these people can only answer questions within there own department. They know little about what the other guy does. One guy works in moisture dispersion, another in limited slip gear additives. The next guy works on compatibility with various metals and rust prevention but nobody knows it all. It is almost like those who say "it is not part of my job description." It drives me nuts because I have to speak to so many different people. I do all this because I am interested in the topic and have been since childhood. Fortunately I have enough education to understand what most people tell me. The thing is that I have to put everybody's information together to get the big picture. It is a challenge and I like these sort of things. The question is how to present the information so that the average person can get some use out of it. I am open to any suggestions. Again, this here is my lastest attempt. aehaas
