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Ranger Gress's Great Oil Debate Documents and Threads The summary of all of this is that there is no consensus. Good lubrication (and cooling) depends on a number of variables, to include 100deg viscosity, high temp shear and zddp levels. Oil and vehicle manufacturers have a lot of concerns other then you and I. Their recommendations are based on their priorities, not yours. General areas of agreement. 1) There is an optimum viscosity for every bearing design. Low viscosity oil can be a problem because it will form a thin "hydrostatic wedge". Too high viscosity oil is bad because flow rates are important and thick oils flow poorly. 2) Good high temp shear #'s are important. Generally high viscosity oils have better high temp shear #'s, but there are some exceptions. An example is Red line's oils where 5W20 has a better high temp shear then most xW30's.That's one reason why you have to look beyond the viscosity grade of the oil. 3) ZDDP #'s were reduced in the last decade by regulatory interference. This was a result of a school of thought that says ZDDP damages catalytic convertors. There is some disagreement with this. The limit is set at 900 ppm. There is some consensus that 1000-1300ppm might be better for our engines. ZDDP acts to protect bearing surfaces from damage due to brief loss of hydrostatic wedge. This is particularly important for the top ends of engines (cam and follower). 4) Newer API Certifications aren't necessarily better for engines. The newer API certifications were more oriented towards (perceived) pollution issues then engine life. 5) E30 owner's manuals recommended 20W50 for high temp operation, but later changed that (high temp) recommendation to emphasize several xW40 oils. Editor's caution, this latter document, while short, requires some puzzling out. 6) Don't blindly trust manufacturer data sheets. Oil blends change faster then websites and data sheets get updated. The only way to know for sure if your oil's chemistry is what you think it is, is oil analysis. 7) Cam and follower lubrication. The top end of a motor has completely different lubrication requirements then the bottom end. Lubrication of the bottom end of a motor is a matter of maintaining a hydrostatic "oil wedge" between the rotating bearing surfaces. Lubrication of the top end is a product of the oil chemistry's ability to keep the follower and cam from gouging each other. The Aussie study below was a particularly good example of this. Note also that contact region surface area, spring pressure and lobe profiles all play major roles. Significant articles and forum threads Turbo Diesel Register: Oil myths Turbo Diesel Register: New API certs aren't always better Oil for Performance Engines. This is a terrific article that is followed by a great FAQs section. It's oriented on Porsche air-cooled motors, but it's entirely applicable to other motors too. Selecting the right oil. This document was written with Corvairs in mind but contains lots of good information. Fuel Economy vs. Wear. Article discusses the latest trend in oils...Fuel economy at the expense of wear. Tests Aussie Oil Tests. Some of the oils tested aren't common in the US, but the test results really hammer home how different the results can be when the oil wedge fails. Oil chemistry matters. Turbo Diesel Register: 8 oils analyzed (first article in the series). Turbo Diesel Register: 21 oils analyzed (second article in the series). Blind studies. Short articles provids lots of nice background on what separates good oils from bad oils. Good, meaning your engine will last longer, not good means latest certifications. Keep in mind that the oils are being analyzed as diesel oils, not oils for gasoline engines. Diesel oils have 2-3X as much detergent as gas oils, so you have to account for that as you consider how the various oils were rated. If a couple oils did poorly because of low detergent content, they might be excellent oils for gasoline engines. Oils on the dyno. The results are not what you would expect.
Specs Valvoline VR-1 Specs. See also Valvoline defends Street Legal VR-1 for high performance engines requiring ZDDP.
ZDDP A parts vender's take on ZDDP and cams. Downward trend in ZDDP in modern certifications.
Background articles and info. Internal Combustion Engine Lubrication. This is the most concise article in this section. BobIsTheOilGuy.com. Link to top of forums. By far the best oil info resource on the net. What oil does inside a bearing. Excellent BobIsTheOilGuy thread on how oil lubricates. 10kpsi at 1k rpm thread. This is a BobIsTheOilGuy discussion of an old oil pressure rule of thumb and whether or not it is of use in selecting oil viscosity. Lubrication Tribology & Motorsport. Analysis of lubrication and power loss in a typical European motor vs. a Formula 1 motor. Bearing Design in Machinery. Google online book. Chp 5 is particularly relevant. |
