Oil is the lifeblood of every engine, so it’s important to always use a high-quality motor oil that meets the vehicle manufacturers’ viscosity recommendations and performance specifications when servicing your customers’ vehicles. Just use a name-brand motor oil that meets the recommended SAE viscosity and current American Petroleum Institute (API) quality standards and you should have no problems, right? Maybe, maybe not.
The caveat is that every vehicle manufacturer has its own requirements for what type of oil should be used in their engines, and those requirements can vary by year, make, model and whether an engine is naturally aspirated, turbocharged, supercharged or a diesel or a hybrid. In other words, there is no one universal motor oil standard that everybody agrees upon.
In the U.S., motor oil viscosity is rated according to SAE standards. The cold- and hot-flow characteristics of multi-viscosity oils such as 5W-20, 5W-30, 10W-30, 0W-40 and so on, are determined by specific test sequences. The first number in a multi-viscosity rating refers to the oil’s cold-flow characteristics, while the second number refers to its hot-flow characteristics. Thus, a 5W-20 oil acts like a straight 5W oil for easier cold-weather cranking and lubrication of critical upper valvetrain components, and it maintains its viscosity when hot like a straight 20W oil for good oil film strength and oil pressure.
Most late-model engines are factory filled with multi-viscosity 5W-20 or 5W-30 motor oil, but some require 5W-40, 0W-20 or 0W-30. It’s important to follow the viscosity recommendations because many of these engines have tighter bearing clearances that require a lower-viscosity oil for proper lubrication. Thinner oils also improve fuel economy. In some applications, such as the Toyota Prius, using the wrong viscosity oil (too heavy) may set a fault code. On others, an oil that is too heavy may interfere with the normal operation of the variable valve timing system, causing additional fault codes to set.
Fortunately, the European and Asian vehicle manufacturers also use the same SAE viscosity ratings as their domestic counterparts, which makes life easier when it comes to choosing an oil that meets a specified viscosity recommendation. The trouble is, not all motor oils actually meet the viscosity ratings that are claimed on the product — and the situation is even worse with bulk oils. According to a recent API survey of more than 1,800 oil samples purchased from bulk dispenser tanks in quick lube shops across the U.S., nearly 20% (one out of five!) failed to meet API standards. Either the viscosity was incorrect or the additive package failed to meet the claimed performance level.
From time to time, another group called the Petroleum Quality Institute of America (PQIA) also audits the quality of branded and private-label motor oils. The results of those tests are published on its website (www.pqiamerica.com). PQIA also issues consumer alerts when it discovers products that fail to meet industry standards.
To address this issue, API created its “Motor Oil Matters” (MOM) program that reminds consumers of the importance of using quality motor oils in their engines. Of course, consumers have no way of knowing what they’re really getting when they have their oil changed, so it’s buyer beware.
To hold service facilities and oil distributors accountable for the quality of the oil they’re selling to their customers, the National Conference on Weights and Measures (NCWM) adopted standards that require shops to list the brand, viscosity and API service category of the oil they sell on their customer invoices.
Starting Jan. 1, 2014, many states are implementing the new NCWM rules and will require service facilities to label bulk containers, print the oil information on all job tickets and retain the paperwork for at least one year. Check with the appropriate government agency to find out if these new rules apply in your state.
OIL QUALITY STANDARDS
Oil quality and performance standards depend on the type of base oils used to formulate a given product (Group I, II, II, IV or V), and the different types of additives that are blended into the oil to improve wear resistance, keep the engine clean, control foaming and corrosion, modify friction characteristics and so on. The relative amounts of these additives and how they’re combined determine the performance properties of the oil — and that’s where things get interesting and confusing.
API rates motor oils differently if they are for gasoline engines or diesel engines. This rating is displayed in a “starburst” symbol on the product. There is also a “donut” that shows the service rating, viscosity and fuel-saving properties of the oil. The current API standard for gasoline engines established since 2011 has been “SN,” which supersedes the previous “SM” rating (2010), “SL” rating (2004) and “SJ” rating (2001). All previous gasoline service ratings are obsolete.
The current API service rating for diesel engines is “CJ-4” (introduced in 2010), which supersedes the previous “CI-4” (2002) and “CH-4” (1998) ratings. CJ-4 oils are primarily for diesel engines burning low sulfur fuels (less than 15 ppm/parts per million), while the previous CI-4 oils are for diesels with EGR systems.
API service ratings are supposed to be backward compatible, and for many applications they are, but there are some exceptions. To help prolong the service life of the catalytic converter and oxygen sensors in late-model OBD II vehicles, the amount of the high-pressure, anti-wear additive ZDDP (zinc dialkyl dithiophosphate) has been reduced. If an engine is using oil, ZDDP can foul the catalyst and O2 sensors, so the amount of ZDDP has been gradually reduced over the years to maintain the emission control systems.
Back in the 1980s, motor oils typically contained around 1,500 ppm of ZDDP. In the 1990s, that was reduced to 1,200 ppm, then it went down to around 800 ppm in 2005. That level of anti-wear additive is adequate for overhead cam engines and pushrod engines that have roller cams, but it has proved to be inadequate for older engines with flat-tappet cams, causing accelerated cam lobe and lifter wear.
So, for these older engines (especially performance engines with stiffer valve springs), a supplemental ZDDP crankcase additive is highly recommended, or a street performance oil that contains higher levels of ZDDP or other anti-wear additives.
ASIAN OIL STANDARDS
A group called the International Lubricant Specification Advisory Committee (ILSAC), made up of Asian and U.S. automakers, has developed its own standards for oil quality. Though not exactly the same as the API standards, the current ILSAC “G-5” rating corresponds closely to the API “SN” rating. The G-5 rating requires improved deposit protection for pistons and turbochargers, more stringent sludge control, improved fuel economy, enhanced emission control system compatibility, seal compatibility and protection for engines using ethanol fuels such as E85. The current G-5 standard has been in effect since 2010, and is backward compatible for the previous G-4 and earlier ratings.
Most branded oil products carry both the API and ILSAC ratings, plus any other vehicle manufacturer specifications that they claim to meet.
EUROPEAN OIL STANDARDS
This is where things get really confusing. Germans like to be precise — very precise — when it comes to specifying motor oils. Audi, BMW, Mercedes-Benz and VW all follow a different set of oil standards called the ACEA European Oil Sequences. Like the API and ILSAC rating systems, the ACEA rating system is based on specific laboratory test procedures. In the U.S., we use various SAE standards and American Society of Testing Materials (ASTM) test procedures. In Europe, they use tests developed by the European Engine Lubricants Quality Management System (EELQMS).
The latest ACEA standards were updated in 2012 and include three basic sets of ratings for gasoline and light-duty diesel engines, light-duty diesel with exhaust after treatment and heavy-duty diesels. Within each of these sets are subcategories that cover different engine performance requirements:
• A1/B1, A3/B3, A3/B4 & A5/B5 for various gasoline and light-duty diesel applications.
• C1, C2, C3 & C4 for catalyst-equipped gasoline and diesel engines.
• E4, E6, E7 & E9 for heavy-duty diesels.
Each subcategory has very specific requirements for viscosity, shear stability, evaporation rates, sulfur and phosphor content, wear resistance, high- and low-temperature performance, sludge resistance and oxidation resistance, according to the application.
Using the ACEA criteria, the European automakers then establish their own standards for which oils meet the requirements for their specific engine applications (much like Ford, GM and Chrysler do in the U.S. using SAE, ASTM and their own proprietary test procedures).
For example, Audi has a number of oil specifications including 501.01, 502.00, 505.00, 505.01, 504.00 and 507.00. Volkswagen has similar specifications: VW 502.00, 505.00 and 505.01. Each number represents a specific oil requirement (much like GM’s “dexos” oil requirement for some of its newer engines).
Bottom line: if an oil does not meet the specific requirement for one of their engine applications, it’s deemed unacceptable by the automaker for use in that engine.
Audi TSB 17-12-29, dated June 26, 2012, lists all of the oils that meet its various specifications. It’s a long list, but some of the familiar domestic oils listed that meet the Audi/VW 502.00 specification include Castrol Syntec Euro Formula 0W-30, Mobil 1 0W-40, Pennzoil Platinum Euro Formula 5W-40 & 5W-30, Pennzoil Synthetic Euro formula 5W-40, Valvoline Synpower MST 5W-30 and Valvoline Synpower HST 5W-40.
The same TSB also lists approved oils that meet the Audi 505.01 specification, and also its 504.00 specification. Each list is different with some overlap, but you can’t assume that if an oil meets one spec that it will necessarily meet other specs.
Therefore, to keep a newer vehicle powertrain warranty in effect when servicing a customer’s vehicle, you should always use an “approved” oil that meets the car maker’s specifications — especially on European vehicles.
You should be able to find out which oils are approved for various makes/models/applications by searching the OEM service literature or an aftermarket repair database. Audi and VW have TSBs that cover this subject, but we couldn’t locate similar information from BMW or Mercedes (they may have it, but we couldn’t find it). BMW says it require its own BMW Long Life 4 motor oil (such as 5W-30, P/N 07 51 0 017 866), but it doesn’t say what other brands meet its specs.
Once a vehicle is out of warranty, any type of oil can be used, provided it meets the vehicle manufacturer’s viscosity recommendations and basic performance requirements. Use the wrong oil such as a bargain-priced conventional oil in an engine that requires a high-quality, long-life synthetic, and the results could be engine damage or failure!
In Europe, long oil drain intervals are the norm. Some European automakers recommend changing the oil every two years or 25,000 miles. To make the oil last that long, the base oil must be a high-quality synthetic with lots of sludge-fighting and engine-cleaning additives. In the North American market, energy conservation is given priority over extended oil life, so motor oils here are usually formulated differently and require changing much more often (every 5,000 to 7,500 miles, or longer depending on the type of oil used and driving habits).
The longer the oil drain interval, the higher the quality of motor oil that should be used, otherwise viscosity breakdown and sludging can become a major problem. Toyota found that out the hard way when it began recommending 7,500-mile and even 10,000-mile oil change intervals a number of years ago. Engine sludging became a problem because the PCV systems on some Toyota engines did not flow enough air to keep moisture out of the crankcase. Moisture accumulation leads to sludge formation and engine damage.
If a customer has his/her oil changed every 3,000, 5,000 or even 7,500 miles, chances are they won’t have any problems using a conventional motor oil, assuming their engine isn’t one that has a marginal PCV system. But, if they’re going beyond 7,500 miles between oil changes, or are relying on an oil service reminder light to signal when an oil change is needed, they could end up having serious problems if they’re not using a high-quality, synthetic oil that has been formulated for extended oil change intervals — which is what most European automakers specify.
Another factor that comes into play with many late-model Gasoline Direct Injection (GDI) engines is the role oil plays in forming intake valve deposits. Deposit buildup has become a problem on some of these engines because the intake valves run dry. The fuel injector sprays fuel directly into the combustion chamber or cylinder, rather than the intake port, so there is no fuel wash to clean and cool the intake valves.
Consequently, if oil is getting past the valve guide seals, it can form heavy carbon deposits on the intake valves that hurt performance and emissions.
A motor oil with a low-volatility rating (its “NOACK” number, which is based on the ASTM D5800 lab test) is better because it reduces oil consumption and helps keep the PCV system and intake valves clean (especially in GDI engines). Most recent European specifications call for a low NOACK rating (less than 15%).