Automotive manufacturers have started using 5W-20 motor oil

Recently two major automotive manufacturers started using 5W-20 motor oil as a factory fill.  Most consumers have many questions about this "new" oil and why after all these years specifying a 5W-30 that they would make the change to 5W-20.  First I must explain that 5W-20 is not a new viscosity motor. 5W-20 has been around since the early 1970's, but not used by consumers or marketed to consumers by manufacturers, until recently.

My research has uncovered the following from a SAE technical paper written by Mobil Research and Development Corp. in 1975. "Research Oil 5 (RO-5) is a conventional 5W-20 viscosity mineral oil product containing an API SE quality additive treatment, but that it may be deficient in some API SE engine performance requirements.  RO-6 is also a 5W-20 viscosity and API quality SE but utilizes all-ester (synthetic) base stock components.  Adequate wear protection with conventional 5W-20 viscosity mineral oils has been difficult to achieve under moderate and high temperature operating conditions."  Mobil's new 5W-20 synthetic formulation, XRN 1669  "has been evaluated in both laboratory and field tests to determine its antiwear performance.  In all cases, wear protection equal to or better than premium API SE quality SAE 10W-40 mineral oils has been provided by this experimental formulation".

Now, keep in mind that this is from almost 30 years ago. My intent here is to show that 5W-20 is not a new viscosity of oil. It just never became widely used. The most popular motor oils back in that era for automotive use were typically 10W-40 and in later years 10W-30 and 5W-30. What this data indicated is that a 5W-20 petroleum oil provides adequate engine protection under normal operating conditions, but does not compare to a premium quality 5W-20 synthetic in moderate and high temperature operating conditions.  The new 5W-20 oils of today are formulated to meet the latest API SL performance specifications and are perfectly suitable for use in your new vehicle that specifies 5W-20, however my personal opinion is that there are superior oils to use that not only meet the 5W-20 performance specifications, but also exceed them.

Here is a brief discussion of some of the most common questions consumers have regarding the 5W-20 motor oil that is specified for their new vehicle.

Question: My owner’s manual species 5W-20 oil.  Do I really need to use 5W-20 oil and why did my 2000 model year vehicle require a 5W-30 oil, while the same engine in my 2001, 2002, 2003, and later engines "requires" a 5W-20 oil?

Answer:   You do not need to use a 5W-20 oil. Do not let your dealer scare you by telling you that you have to use it for your warranty.  That is a tactic that some dealerships use to scare customers. Once you know the facts and the Federal Magnusson Moss Act law you will be much better informed to protect your rights and use the type of oil you want to use.

One of the main reasons 5W-20 was specified for your engine is to increase the CAFE (Corporate Average Fuel Economy) reported to the Federal Government.  CAFE is the combined average fuel economy of all of a vehicle manufacturers product line.  Minimum CAFE levels are specified by the Federal Government.  In order for a vehicle manufacturer to continue selling profitable large trucks and SUV's, which typically have poor fuel mileage ratings, as compared to smaller cars, and still meet mandated CAFE requirements, they must also sell enough of the smaller cars which have much better fuel economy ratings to offset the poor fuel economy ratings of the larger vehicles.  The change to a 5W-20 oil will allow a manufacturers overall CAFE to increase by a very small amount, typically in the tenths of a mile per gallon range.  5W-20 oil is a lighter viscosity than a 5W-30 oil and therefore has less internal engine frictional losses, or less drag on the crankshaft, pistons and valve train, which in turn promotes increased fuel economy.  This increased fuel economy is virtually undetectable to the average motorist without the use of specialized engine monitoring and testing equipment under strictly controlled test track driving when compared to a 5W-30, 10W-30 or a 0W-30 viscosity motor oil.

Question: Could using a 5W-30, 10W-30, 0W-30 or even a 10W-40 or 20W-50, oil in my vehicle which specifies a 5W-20 oil void my new car warranty?

Answer:  Absolutely not. Vehicle manufacturers recommend using motor oils meeting certain viscosity grades and American Petroleum Institute service requirements. Whether a motor oil is a 5W-20, 0W-30, 5W-30, 10W-30, 10W-40, 15W-40 or 20W-50 (for certain racing and high performance applications) or even a synthetic vs. a petroleum based oil will not affect warranty coverage. The manufacturer is required by Federal Law to cover all equipment failures it would normally cover as long as the oil meets API service requirements and specifications and was not the cause of failure.  In addition, the Federally mandated Magnuson - Moss Act states that a manufacturer may not require a specific brand or type of aftermarket product unless it is provided free of charge.  If your dealership continues to tell you that you must use 5W-20 motor oil and or/ a specific brand of 5W-20 motor oil (and will not provide it free of charge), then ask them to put it in writing and then contact an attorney.  Their position is inaccurate, and, in fact violates existing law.

Additionally, if there is ever a question of whether or not a particular motor oil was the cause of an engine failure make sure to get a sample of the used oil in a clean bottle, typically 6 oz. minimum. The oil can then be sent to an independent ASTM certified testing lab for analysis.  This is standard procedure for most commercial vehicles, trucking, construction/excavation and fleet companies and there are many certified test labs all over the country.  Remember, a knowledgeable and informed consumer is your best defense against being taken advantage of by a car dealership service center.

Question:  My car dealership service center states that I must use 5W-20 because the oil passages inside my engine are smaller and a higher viscosity oil will not properly flow through them. Is this a true statement?

Answer: Absolutely not. That is ridiculous to assume that a manufacturer would purposely make the oil galleys and passages smaller. There is no technical or cost/performance benefit to doing this whatsoever. My inspection of oil galleys, pistons, bearings, crankshafts, oil pumps and passages from pre-5W-20 engines to the same size and brand of engines that specify 5W-20 indicate there are no measurable differences in the oil passages in these components.

For those consumers that still desire to use a 5W-20 oil, once again one specific manufacturer, AMSOIL INC., does manufacture an excellent extended drain interval 5W-20 synthetic motor oil, called XL-7500 5W-20. It is a 7500 mile/6-month motor oil and the only 7500 mile/6-month 5W-20 on the market that I am aware of.  AMSOIL's 5W-20 synthetic motor oil provides outstanding wear protection and increased power, performance and fuel economy in high and low temperatures and also meets and exceeds the manufacturers specifications. Other conventional 5W-20 motor oils must be changed at the manufacturers specified change intervals. If 5W-20 becomes more popular and widespread in use in the coming years more oil companies may offer 5W-20 oils, however at this time the selection is not as varied as with other viscosity motor oils

My personal recommendation is for even better performance and protection to use AMSOIL's Series 2000 0W-30 synthetic motor oil. This is the top performing AMSOIL Synthetic Motor Oil for gasoline powered light trucks and passenger cars.  It uses race-proven technology and provides unsurpassed fuel efficiency and superior wear protection than other conventional and synthetic motor oils. It is a 35,000 mile/1-year change interval motor oil. Use it in conjunction with AMSOIL's Absolute Effeciency Oil Filter's that specify a change interval of 25,000 miles/1-year, whichever comes first.

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