The chart shown below was part of an article written by a gentleman and posted to the newsgroups. He has compiled important data regarding many of the top conventional and synthetic oils on the market and put them in a chart for easy comparison. Along with this chart he has provided some descriptions of what the numbers represent. These figures have not been updated recently on this page. For the latest numbers please see our AMSOIL tech bulletins and compare with the latest tech specs from manufacturer websites. Please take note that at the time of this compilation the only two oils that really match up with AMSOIL (according the figures below) are Mobil 1 and Red Line. These are both exceptional oils, but you will find that in most viscosity grades AMSOIL's specs (if taken as a whole) come out better than both of them. It should also be said that these specifications, although helpful in determining the general quality of an oil, do not tell the whole picture. Noack volatility test scores and wear scar tests are also very important, and in these two areas AMSOIL stands on top for every test we've seen. In fact, Mobil 1's new Tri-Synthetic 5W-30 and 0W-30 formulations are actually now surpassed by most other synthetic oils we've tested on the ASTM Four Ball Wear Test. Also important, but not listed in the charts below, is the fact that AMSOIL Synthetic Oils use more top quality base stocks than any other oil and have a better detergent additive package as well. That, coupled with their superior air and oil filtration technologies, make AMSOIL Synthetic Oils and automotive products the best choice out there for anyone who wants improved performance and considerable pocketbook savings. Here is the Newsgroup Article: First, I will answer a couple of questions asked by another. Yes, it is OK to mix mineral and synthetic oils. One of the early synthetics used was a Polyalkylene Glycol. This was totally incompatible and would gel when mixed. This has not been used for years for automotive lubrication. All common synthetics used for engine lubrication now days are a Polyalphaolefin (Mobil 1) or a Dibasic Organic Ester type (AMSOIL). These are fully compatible with conventional oils. In fact Golden Spectro and AGIP Sint 2000 are mixtures of mineral and synthetic oils. It is always best to mix oils with the same rating (SG). This insures that the additive packages are compatible and will maintain their effectiveness. All engine oils use an organic Zinc compound as an extreme pressure/anti wear additive. Spectro adds more to their Motorcycle oil than to the car oil because Zinc is a poison to catalytic converters. You will also see that some "car" oil contains more than their motorcycle oil. The difference in Zinc content between ..11% and .16% is insignificant to the converter. The little data I saw on the oils packaged by the motorcycle manufacturers indicated that they were no better than the top automotive oils. While most were good, they didn't offer anything the cheaper oils do. (They are in reality just repackaged and in some cases slightly reformulated top grade auto oils). The following is a slightly modified repost of my original article. I have added a few bits that address some FAQ's. (long) Choosing the best motor oil is a topic that comes up frequently in discussions between motoheads, whether they are talking about motorcycles or cars. The following article is intended to help you make a choice based on more than the advertising hype. Oil companies provide data on their oils most often referred to as "typical inspection data". This is an average of the actual physical and a few common chemical properties of their oils. This information is available to the public through their distributors or by writing or calling the company directly. I have compiled a list of the most popular, premium oils so that a ready comparison can be made. If your favorite oil is not on the list get the data from the distributor and use what I have as a data base. This article is going to look at six of the most important properties of a motor oil readily available to the public: viscosity, viscosity index (VI), flash point, pour point, % sulfated ash, and % zinc. Viscosity is the measure of how thick an oil is. This is the most important property for an engine. An oil with too low a viscosity can shear and loose film strength at high temperatures. An oil with too high a viscosity may not pump to the proper parts at low temperatures and the film may tear at high rpm. ****Our .02 again-- Viscosity INDEX or VI in the chart below is a measure of how much an oil's viscosity changes with temperature changes. The higher the VI, the less change that occurs and the better the protection.**** Flash point is the temperature at which an oil gives off vapors that can be ignited with a flame held over the oil. The lower the flash point the greater tendency for the oil to suffer vaporization loss at high temperatures and to burn off on hot cylinder walls and pistons. The flash point can be an indicator of the quality of the base stock used. The higher the flash point the better. 400 F is the minimum to prevent possible high consumption. Flash point is in degrees F. Pour point is 5 degrees F above the point at which a chilled oil shows no movement at the surface for 5 seconds when inclined. This measurement is especially important for oils used in the winter. A borderline pumping temperature is given by some manufacturers. This is the temperature at which the oil will pump and maintain adequate oil pressure. This was not given by a lot of the manufacturers, but seems to be about 20 degrees F above the pour point. The lower the pour point the better. Pour point is in degrees F. % sulfated ash is how much solid material is left when the oil burns. A high ash content will tend to form more sludge and deposits in the engine. Low ash content also seems to promote long valve life. Look for oils with a low ash content. % zinc is the amount of zinc used as an extreme pressure, anti- wear additive. The zinc is only used when there is actual metal to metal contact in the engine. Hopefully the oil will do its job and this will rarely occur, but if it does, the zinc compounds react with the metal to prevent scuffing and wear. A level of .11% is enough to protect an automobile engine for the extended oil drain interval, under normal use. Those of you with high revving, air cooled motorcycles or turbo charged cars or bikes might want to look at the oils with the higher zinc content. More doesn't give you better protection, it gives you longer protection if the rate of metal to metal contact is abnormally high. High zinc content can lead to deposit formation and plug fouling. The Data: Listed alphabetically --- indicates the data was not available **figures last updated April 1998 VI is Viscosity Index                        Explanation of Specs. Brand  VI Flash Pour %Ash %Zinc 20W-50                       AMSOIL 155 474 -47 0.05 ---- Castrol GTX 122 440 -15 0.85 .12% Exxon High Perf 119 419 -13 0.70 .11% Havoline Formula 3 125 465 -30 1.00 ---- Kendall GT-1 129 390 -25 1.00 .16% Pennzoil GT Perf. 120 460 -10 0.90 ---- Quaker State Dlx. 155 430 -25 0.90 ---- Red Line 164 503 -49 0.85 ---- Shell Truck Guard 130 450 -15 1.00 .15% Spectro Golden 4 174 440 -35 ---- .15% Spectro Golden M.G 174 440 -35 ---- .13% Unocal 121 432 -11 0.74 .12% Valvoline All Climate 125 430 -10 1.00 .11% Valvoline Turbo 140 440 -10 0.99 .13% Valvoline Race 140 425 -10 1.20 .20% Valvoline Synthetic 146 465 -40 1.50 .12%   Brand VI Flash Pour %Ash %Zinc 20W-40                       AMSOIL 124 500 -49 ---- ---- Castrol Multi-Grade 110 440 -15 0.85 .12% Quaker State 121 415 -15 0.90 ----   Brand  VI Flash Pour %Ash