Modern motor oil madness

As it turns out, there are only a small handful of companies who make the base stock for all motor oils. A few more companies make the additive packages, which then determines how the oil performs. The rest is primarily a tiny bit of customizing combined with a lot of marketing. That favorite brand you swear by? Probably not a distinct advantage over another brand. Viscosity, conventional, synthetic, semi-synthetic and API rating are all still relevant, but by far are not the biggest deal breakers when it comes to selecting the correct oil for that modern engine that comes into your shop for service. Selecting the correct oil weight and API rating these days is like selecting tires that are round, black and the correct diameter. It would be an understatement to say we need to know a little more to make the right selection on those tires. The same is true with motor oil. At the end of the very excellent in-depth oil class, I asked the instructor (Kevin McCartney) two simple questions:

1.  How many different motor oils would a shop need to carry to service most domestic, Asian and European vehicles? He thought for a few seconds and replied “at least 12-15, but preferably closer to 20.”

2. How many oils do most shops carry in your estimation? His response? Most have six or fewer.

So what’s the difference?

One fact I learned, which seemed a bit provocative at the time, was that one multi-weight 5W-30 oil maybe thicker or thinner than another 5W-30 oil. Really? Yes, really! This has little to do with the brand. It’s mainly about the oil specifications that go beyond the worn-out convention of thought most of us refer to as viscosity. Just consider how different engines are. Smaller in displacement, higher revs, increased temperatures, tighter tolerances, the growing popularity of turbo chargers, and more exotic materials/metallurgy can be a real challenge for lubrication engineers.

We also must remember that oil does more than just lubricate. It cools, cleans, seals and protects, too. In addition to the traditional problems of low oil levels and lack of maintenance causing major lubrication problems, the incorrect oil can lead to timing chain issues, GDI pump drive failures and catalyst poisoning. Now I don’t think there are very many techs, no matter what their current motor oil IQ, who would consider pouring 5 quarts of 10W-30 oil into a quarter-million-dollar exotic sports car. Most passenger car engines today are more similar to an exotic sports car’s engine than they are to the old small-block Chevys that often ran for hundreds of thousands of miles with very little thought to the nuances of oil specifications.

Viscosity 101

All oil has a thickness, which varies with temperature, referred to as viscosity. Viscosity is the primary quality of a lubricant that influences the lubricant’s efficiency. The viscosity value assigned to the oil (let’s use a simple straight weight of 30 for the example) is simply the oil’s resistance to flow via gravity at a particular temperature. The higher the number, the greater the resistance to flow. This resistance to flow through a calibrated tube over a fixed period of time at a set temperature is called Kinematic Viscosity. Naturally, the colder something is the thicker it is. With a multi-weight oil, that thickness can be changed to vary with temperature so it’s not too thick when it’s cold and not too thin when it’s hot. If additives are introduced into the oil by the oil producer to cause the oil to take on a different kinematic viscosity throughout a range of temperatures, the oil is assigned a viscosity rating number such as 5W-30. 5W-30 is as thin as 5 weight oil when measured at -22°F. and thick as 30 weight when the oil is measured at 212°F. The “W” stands for “Winter” by the way, not weight.

Viscosity numbers – Printed and hidden?

The other side of viscosity is a number that is not printed on the bottle of oil. That viscosity is referred to as Dynamic or Absolute Viscosity. Dynamic viscosity can best be described as how the oil performs in functions other than the resistance to moving through a passage (think bearing clearance) at a set temperature over a period of time. One way to picture this difference is to compare the pouring nature of two different substances to the stirring resistance of those same two substances.

For example, cold honey pours easier than cold mayonnaise but is harder to stir. Lubrication laboratories will often use a test apparatus (called a capillary tube viscometer) containing a set of tubes for oil to move through to test Kinematic viscosity; they use another apparatus (called a rotary viscometer) that checks the oils’ resistance to being stirred. Perhaps this is a slight oversimplification, but the viscosity rating of the oil printed on the oil container is the oil’s resistance to pouring and the other viscosity rating not printed on the container is the oil’s resistance to being stirred. Both are important aspects of the oil. The hidden spec for Dynamic viscosity (stirring nature of the oil) is how two oils of the same brand, API rating and type (conventional, semi-synthetic or full synthetic) can be quite different. This is how the statement made previously, that one 5W-30 oil can be “thicker” than another 5W-30 oil, can make some sense. The different dynamic viscosity may affect other functions of the oil, such as how it reacts when the lubrication system uses splash oiling (i.e. timing chains) as opposed to moving through main and rod bearing clearances.  

Additive packages

The chemical process that takes place to modify the carbon chain of the oil to make it a multi-weight is well beyond my ability to explain in a short article, but there is one thing to take away from that process: the additives added to the oil base stock account for between 15 percent and 25 percent of the oil. In addition to viscosity index improvers, oil additives also contain elements such as dispersants to prevent sludge formation, pour point depressants, antifoaming additives, detergents (to prevent acid formation) rust and corrosion inhibitors, antioxidants and anti-wear agents to reduce wear under heavy load and high temperatures. By just looking at the list of things reduced or prevented by the oil’s additives package, it’s easy to see that the oil’s “ad pack” is very important. For example, antioxidants slow down the main cause of lubricant degradation in the engine, which is the breakdown of the base stock due to oxygen and heat. Oxidation of the base stock causes acid formation, which leads to corrosion and sludge/varnish, which leads to blockages to oil flow.

One additive that has changed for modern motor oil is zinc dialkyl dithio phosphate (ADDP). Zinc can be hazardous to the health of a catalytic converter. As you well know, cats rarely die of natural causes. They are “killed” by overly high temperatures (sustained rich mixtures) and the poisons that can be induced via the gasoline, coolant (when coolant leaks into the combustion chamber) and motor oil.  The cat-killing problem is such a factor that the EPA has been encouraging oil makers to limit or eliminate the use of zinc. Alternatives to ADDP are very expensive. Off-brand oil companies who produce the cheaper oils are naturally going to fudge their testing results using older standards.

Oil specifications: It’s good oil – my supplier promised!

We’re all receptive to a bargain when it comes to providing our customers with a good product that also gives our shop a great return in profit. The problem with bargains is they aren’t always a bargain in the long run. When it comes to oil specifications, the API rating on the oil container (donut-shaped label) contains a standard that used to be a large part of the defining factor on whether an oil of the correct weight should be used in a particular engine. An API rating for gasoline engines on passenger cars and light-duty trucks consists of two letters. An example of the latest API spec would be SN. The S stands for service. Heavy-duty gas and diesel engine oil contains two letters and a digit, such as the latest diesel spec CJ-4. The “C” stands for commercial.

Today’s increased demands for the right oil required for modern engines have caused the API standard to all but move into the category of irrelevance. Obviously, as in years past, you don’t want to grab a bottle of oil marked API SE from Grandpa’s cabinet and put it into your late-model Ford. It might be fine for that old unrestored classic car in Grandpa’s garage, though. The latest (since 2010) API rating of “SN” is fine to put in the old classic car as well as the brand new vehicle. As stated previously though, the weight and API number are like saying “I have a round and black 19-inch tire to put on this car.” Let’s hope you have the correct aspect ratio, rolling circumference, tread/temp/traction rating, sidewall stiffness and more, or your customer is not going to be happy. The same is true to the API rating and weight. They are only two pieces of the specification puzzle.

So how do you properly spec oil out? Start out by determining the International Lubricant Standardization and Approval Committee (ILSAC) requirement for most domestic and Asian OEMs or the European Automobile Manufacturer's Association (ACEA) specification for European OEMs. Keep in mind that there are variations above and beyond ILSAC and ACEA, though. For example, the GF5 ILSAC specification that is commonly associated by many techs with GM’s dexos oil specification isn’t necessarily dexos rated. An oil that is ILSAC GF5 may be able to pass GM’s tests, but due to the associated licensing costs with having that oil GM certified with the dexos label, it may have simply have never received that certification. One the other hand, that particular GF5 oil may not be able to get GM’s dexos certification for a valid reason. So don’t just assume a GF5 is dexos. For your GM customers’ vehicles with the dexos requirement, always look for the GM dexos label.

Beyond ILSAC and ACEA is the exact engine builder/OEM manufacturer’s specifications. These numbers vary widely so don’t even try to make sense of them. Keep in mind that there may be multiple OEM oil specs per application.

Synthetics: Are they really better?

Even with the higher cost as a disadvantage, the list of advantages of synthetic oil is substantial. Synthetic oil has superior low-temperature properties, better high-temperature stability, lower volatility, longer oil life, and responds better to additives compared to mineral (conventional) oil.  Plus, the lower friction nature with synthetic oils result in higher fuel economy compared to the same weight of mineral oil. When they are required, use them. Otherwise, a combination of personal preference combined with the vehicle’s particular situation (performance/load related high temps) may be the factors that lead you to advise your customers to use a synthetic when it’s optional.

Maintenance mishaps

A lack of correct oil change intervals can wreck an engine’s basic mechanical essentials. A plethora of technical advances — ranging from displacement on demand to variable valve timing — demand great oil condition as well as the correct oil. Dilution from overly rich mixtures, disregarding OEM warnings against using additives, and even severe driving styles all break down the oil’s additive package and turn things to sludge. Then there’s the weird stuff like phantom engine ground issues that can lead to micro arc. Micro arc occurs when a bad ground to the engine causes moving parts inside the engine that don’t normally act as a ground to do so with a tiny arc. In the oil pan/oil galley, that arc shears the carbon chain length and now you have the incorrect viscosity. So in addition to the obvious things, the more we know on anything including seemingly mundane things like motor oil, the more problems we can avoid down the road.

Now confession time. Being the busy travelling tech trainer that I am, combined with my inherited desire to do it right myself (thanks Dad), I still perform most all out of warranty service (including LOFs) on the vehicles in my household. I have a 2013 Malibu Eco (hybrid stop/start BAS) that is now well past the 100K mile mark. In spite of the highway miles, I should have changed oil more often. The voice of common sense and technical reason said “don’t dare follow that Oil Life Monitor (OLM) like an uninformed consumer.” But I did follow that dang OLM — to a degree — but never getting below 40 percent. It was during one of those 40 percent oil life remaining LOFs that I noticed the mileage driven since the last oil change had reached 11K. 11,000 miles? I lowered my head in professional shame and prayed for engine longevity grace.

Then the ticking started. The ticking was a timing chain and follower in a few pieces that ended up in the pan. Shortly after that the knocking started. Loud crankshaft main bearing knocking. Fortunately, that lump in my throat went away when it was discovered the GDI pump cam follower had worn down from my LOF neglect. I looked at some of the 5 qt. containers of 5W-30 Mobile 1 (full synthetic) now filled with used oil sitting under a workbench. A few of them did not have the logo on them. They were the “high mileage” Mobile 1 oil with ACEA (instead of ILSAC GF5) on the back . . . and that GM dexos logo was nowhere to be found on the jugs. Wrong oil — whoops, major screw up again. But prayers were answered because it all turned out fine. A great Chevy dealer service manager in my hometown applied the extended powertrain warranty and my problems all went away. Well, all except for the guilt. I wish I would have had that class on motor oil a long time ago. But as they say — better now than never!