How to Choose the Right Oil

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How to Choose the Right OilThis is probably the number one question that I receive from people. “How do Iknow what oil to use for MY vehicle?” There are actually a number of precedingquestions you need to ask yourself long before you can effectively answer thismore general, but extremely important, question.Motor oil is the most important component of your engine. Without it, yourengine dies. With the wrong oil, your engine dies slowly. Getting it right reallydoes matter. Use this guide to help you make the best selection possible so thatyou can get as much life as possible out of your engine.MOTOR OIL TYPEFirst and foremost, do not overlook the fact that viscosity is not the only criteriacritical to proper motor oil selection. You must choose an oil that is matched toyour application with regards to it's formulation and design, specificallybasestocks and additives used. For example, if you are running a diesel engine,then you had better be sure the oil you choose is rated for diesel engines.Similarly, if you are running a gas engine, then the oil should be formulated foruse in gasoline engines.Of course, sometimes, an oil can be rated for both gas and diesel use. However,your oil should meet at least the minimum API specifications required for YOURvehicle. For instance, if your vehicle manual calls for an API SL oil (which is agas engine oil specification), then your oil should specify that it meets/exceedsthat minimum standard (in other words, it should be rated for API SL, SM, ...). ItMAY meet other specifications as well, but it MUST, at a minimum, meet the APISL specification.Likewise, if you are running a diesel engine and your owner's manual specifiesthat you should only use API CI-4 oils, then you should not use an oil that isonly rated for CH-4. This is not a recent enough specification. However, if the oilyou are considering indicates that it meets API CJ specs, then you're ok, since “J”comes after “I”. API specs are generally “backwards compatible”, meaning thatthe CJ spec also is appropriate for use in vehicles calling for CI, CH, CG, CF, etc.(all PREVIOUS API diesel classifications).Moreover, some vehicle manufacturers will specify OEM specific ratings that anoil must also meet. This is more common with European vehicles, but isbecoming more common with US manufacturers as well. So, if your owner'smanual says that your oil is to meet BMW specification XYZ123, then you hadbetter make sure that the oil you're considering indicates that it meets that OEMspec.SYNTHETIC OR PETROLEUMThis is a question that is actually a relatively critical one IF you have any concernover how long your vehicle/engine should last. There are plenty of situationsthat do NOT warrant the use of synthetic oil, and you may very well be in one ofthose situations, depending upon your vehicle, how you drive, where you driveor how long you intend to keep your vehicle. Of course, it is just as likely thatyour situation may very well warrant the use of synthetic oil, and the decisionregarding which you should choose is not necessarily a simple one.The truth is, there are MANY variables that affect this decision, not the least ofwhich is just how much trust you put in a synthetic oil to offer enhancedprotection and possibly extended oil drains. Some of the many benefits thatsynthetic oils offer can only be taken full advantage of if you actually trust themto offer those benefits and push the oils beyond what a conventional petroleumoil could accomplish.By now, if you've read the preceding chapters of this book, you already knowwhat you need in order to make an educated decision in this regard.THE VISCOSITY QUESTIONIn most cases you can simply go with the manufacturer's recommended viscositygrade. Of course, if you're considering a synthetic oil, it is generally very safe togo to a lesser “w” rating than what is recommended by the manufacturer(although the higher the quality of the synthetic, the more true that statement is).For instance, if the manufacturer recommends a 10w30 viscosity (and isn'talready specifying the use of synthetic oil), then you would be safe to use a 5w30or 0w30 synthetic oil.Generally (see below for exceptions), if the vehicle manufacturer specifies anXwY viscosity oil (such as 5w30, where “X” is “5” and “Y” is “30“), under mostcircumstances you should stick with the same “Y” value, but can go to a lesser“X” value to improve cold weather performance and possibly fuel efficiency.However, in my opinion, you should ONLY do this if you're moving to asynthetic oil and synthetic is NOT already being specified by the vehiclemanufacturer.In other words, if your vehicle manufacturer is calling for a 10w30 SYNTHETICoil, then, although you MAY be able to go to a 5w30 synthetic oil, I, personally,would not recommend it without some significant investigation into the issue.On the other hand, in nearly all cases, if the vehicle manufacturer is calling for a10w30 oil and does NOT specifically indicate that you should use a synthetic oil,then, you should be able to EASILY move to a 5w30 synthetic oil, and possiblyeven a 0w30 synthetic oil with no trouble at all.If the manufacturer specifies multiple viscosities that can be used in your vehiclebut does NOT specify the need to use synthetic oil, then a petroleum oil of ANYof those listed viscosities would be fine, although, the conditions under whichthe vehicle will be driven would dictate whether to stay at the “high end” or“low end” of the viscosity range listed.Will you be driving in cold temperatures mostly? Go with a lower viscosity.Congested city driving where engine temps can rise considerably? Heavytowing (same heat issues)? Do you live in a very hot climate? Stay at the higherend of the scale.All of these and other driving conditions should be taken into account in tryingto find the BEST viscosity for your application. However, ANY of the listedviscosities should be adequate, even if using petroleum oil, since themanufacturer is not specifying synthetic as being mandatory.In contrast, if the vehicle OEM is NOT specifically calling for synthetic, butyou're planning on going that direction, then, nearly always, you can safely stickto the lowest “Y” value listed and could even go to a LOWER “X” value. So, forinstance, if the manufacturer said you could use 10w30 or 10w40 in your vehicle,unless your application falls under one of the exceptions below, you could safelystick to an Xw30 oil (using the lowest “Y” value listed) and you could go with a0w30 or 5w30 oil safely, even though the manufacturer listed only 10w options.Don't Thicker Oils Offer Greater Protection?The cop-out answer is SOMETIMES. Thicker isn't always better - even whenusing a petroleum oil. Although it is true that heavier viscosity oils (which aregenerally thought of as being “thicker”) will hold up better under heavy loadsand high temperatures, this doesn't necessarily make them a better choice for allapplications.NOTE: When I refer to higher or heavier viscosity oils, I'm referring to the“second” number of a multi-viscosity specification. In other words, a 10w40would be heavier than a 10w30 because 40 is higher than 30. I'm not making anyreference to the “w” rating because this doesn't come into play unless you'rereferencing cold temperature performance.You see, on many newer vehicles only 5w30 or 10w30 motor oils arerecommended by the manufacturer. If you choose to use a higher viscosity oilthan what is recommended, at the very least you are likely to reduceperformance of the engine. Fuel economy will likely go down. Engineperformance will likely drop.In the winter months I would highly recommend that you not use a heaviergrade oil than what is recommended by the manufacturer. In cold startconditions you could very well be causing more engine wear than when using alighter viscosity oil. In the summer months, going to a heavier grade is less of anissue, but there are still some things to be aware of.Moving one grade up from the recommended viscosity is not likely to cause anyproblems (say from a 10w30 to a 10w40 oil). The differences in pumping andflow resistance will be slight. Although, as was mentioned, efficiency of theengine will decrease, the oil will likely still flow adequately through the engineto maintain proper protection, and, under certain circumstances (heavy load,high RPM), you MAY see improved protection with this heavier oil.Moving two grades up from the recommended viscosity (say 10w30 to 20w50) isa little more extreme and could cause long term engine damage if not short term.Here's the thing. Although the oil will still probably flow ok through the engine,it is a considerably heavier viscosity oil. As such it will be more difficult to pumpthe oil through the engine.More friction will be present than with a lighter viscosity oil. More frictionmeans more heat. In other words, by going to a heavier weight oil, you mayactually be causing more heat build-up within the engine. You'll still beproviding adequate protection from metal to metal contact in the engine bygoing with a high viscosity, but the higher viscosity will raise enginetemperatures.Over the short run, this is no big deal. However, over the long term, whenengine components are chronically run at higher temperatures, they WILL wearout more quickly. As such, if you intend on keeping the vehicle for awhile, keepthis in mind if you're considering using a heavier weight oil than themanufacturer recommends.The key is to generally stay away from viscosity grades that are not mentionedin your owner's manual. Sometimes vehicle manufacturers will make referenceto the possibility of using a 10w40, 15w40 or 20w50 motor oil, even though theymight recommend a lighter weight oil for most situations.If this allowance is made, you'll be ok using a heavier grade of oil. You'llprobably see a drop in mpg using the heavier oils, but you will not likely causeany long term engine problems. I would recommend, however, to stick with thelower weight recommendations if using a synthetic oil, even if you're runningthe engine in higher temp climates. I think you know why by now.If the manufacturer does not make allowance for heavier weight oils, it would bemy recommendation that you DO NOT use a heavier weight oil in your engine.Under most circumstances, stick with a viscosity grade that is recommended bythe manufacturer. And, if you do choose to use a heavier weight oil, at leastmake sure that you only move up one grade. Never move up two grades.Exceptions to the Above Rule1. If yours is a racing application, more investigation would be necessary todetermine the proper viscosity to be using in your engine.2. If yours is a heavy duty application where your vehicle is being subjectedto EXTREME service such as towing extremely heavy loads, you maywant to consider going to one of the heavier recommended viscosities.3. If you are not comfortable venturing outside of OEM viscosityrecommendations, then, by all means stick with what your vehiclemanufacturer recommends. OEM viscosity recommendations will beperfectly safe for your vehicle and will make your selection process easy.Specialized CasesIt is possible, depending upon how you are using your vehicles or equipment,that a more extreme divergence from the OEM viscosity recommendation mightbe appropriate. However, if you think this may be the case, before making thedecision to diverge entirely from the manufacturer's viscosity recommendation,please do your homework.MOTOR OIL QUALITY COMPARISONSOnce you've managed to decide the type and viscosity of oil you shouldprobably be using, the question then comes down to determining which of theoils that meet your criteria are the best of the bunch. In most respects, the onlyway to really make that determination is to check the specs. It's not a perfecttechnique, since the specs can “lie” in some ways, but, it's the best option you'vegot. *This article is taken from The Motor Oil Bible