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Oil upgrades by the letters and numbers

Say what you will about the technological marvel that is a modern engine, but they all require motor oil as their first line of defence. And at no time has the quality of your oil been more important ...


The research continues.(Cummins photo)
The research continues.

(Cummins photo)


Say what you will about the technological marvel that is a modern engine, but they all require motor oil as their first line of defence. And at no time has the quality of your oil been more important than it is today, as it’s expected to handle ever-higher soot loads that come with environmentally friendlier engine designs.

Most on-highway trucks use standard 15W-40 multigrade engine oil. The numbers, 15 and 40, respectfully refer to the viscosity of the oil, or its resistance to flow, at various operating temperatures. The first number, 15W (W is for winter), means the oil has a viscosity rating of 15 when cold, meaning it is formulated to be thinner to allow for cold-weather starts. At higher operating temperatures, the same oil is formulated to thicken to a viscosity rating of 40.

The key to distinguishing one 15W-40 oil from another though, lies more in the letters on the can than in the numbers.

Diesel engines manufactured in North America generally specify a certain API (American Petroleum Institute) service standard – denoted, as on the bottles of oil, as some level of “C” (for compression ignition) grade. The standard signifies that the oil allows the engine to operate within certain environmental parameters, provided specified change intervals are met. But diesel emission requirements, which are set by the U.S. Environmental Protection Agency, have been evolving rapidly, forcing the manufacturers to establish ever-higher operating standards for engines and, therefore, engine oils.

“The last 10 years has been a period of huge, huge change in this industry, and emissions have been the driver for everything we’ve done,” says Crawford Smyth, a Calgary-based category manager for Shell Canada. “As fast as one standard was developed, there was another there to replace it.”

The first emissions-related engine-oil standard, the CE classification, came into force in the late 1980s. The CE standard established a particulate-emission ceiling of 0.6 grams for every horsepower burned in an hour (g/hp-hr), and 10.7 g/hp-hr for nitrous oxide (NOx), both of which make up the soot pumped out in the combustion process and contribute to smog. That was followed in 1991 by the classification CF-4 and, in 1994, by CG-4. The current standard is CH-4, introduced in November 1998, when allowable emissions tightened to 0.1 g/hp-hr for particulates and 4 g for NOx. While oil formulated to meet the current standard works well in an older engine, below-standard oil is simply not formulated to handle the stresses of more compact modern engine designs.

The challenge currently facing the manufacturers of both engines and lubricants is the latest EPA emissions regulations, scheduled to come into force on Oct. 1, 2002. The new oils, known as PC-9 in the industry, will have to address a drop in the ceiling for NOx to 2 g. To meet the tightening requirements, engine manufacturers have done such things as reduce fuel-injection timing, which also lowers combustion efficiency and raises soot production by as much as 500 per cent. So if that soot isn’t allowed to go up the stack anymore, where is it going? You guessed it – into the engine oil.

“A few years ago, the trend was toward lean-burning engines, which improved fuel economy but created more NOx,” Smyth says. “But the EPA came down hard on the engine manufacturers and handed out some big fines. So the industry changed the engine electronics to deal with that and ended up with increased soot levels. (The next series of standards is expected to require such things as Exhaust Gas Recirculation.) But that upset some oil buyers because it increased the drain intervals; if the oil gets dirtier faster, it has to be pulled out faster.”

Soot doesn’t dissolve in engine oil: it gets suspended so it can’t form larger particles that could wear engine components or collect to form sludge. The trick for lubricant engineers is to formulate the oil such that it can disperse large amounts of soot without thickening out of grade. For example, a 15W-40 that has thickened to a 20W-50 provides inferior low-temperature starts and reduced wear protection.

In the future, an oil’s ability to deal with the soot problem, while delivering the same wear protection and drain intervals, will separate premium products from the rest of the pack.

So the race is on.

“We are already formulating now with 2002 in mind,” says Ellen Falconer, an oil product-line advisor for Imperial Oil. “But we are formulating new oils all the time, really. We spend a tremendous amount of money on research, and that’s just the ticket to the game if you want to be considered a premium brand.”

Unfortunately, Falconer says, engineers are designing lubrications for engines that are still just being designed. Smyth confirms this.

But assuming viscosity grades and performance standards are the same, how can consumers distinguish one heavy-duty engine oil from another? Well the short answer is, they can’t, at least not by looking at the bottles.

Every brand of oil is a finely mixed chemical cocktail, engineered to achieve certain characteristics. In truth, the base oil-stock only accounts for about one per cent of most mineral oils, and there are also different classes of base stock. For the most part, engine oil is made up of various additives (five to 10 per cent), viscosity improvers (10 to 20 per cent) and various inhibitors (75 to 80 per cent). The additives and inhibitors are there to improve lubrication and protect the engine from deposits, wear, friction, rust and other corrosives. The viscosity improvers stop the oil from foaming and breaking down.

By mixing these chemicals in varying amounts, lubricant engineers can formulate a particular oil to provide optimum performance under certain operating conditions. These could include unusually hot or cold operating environments, stop-and-go driving, severe service applications, frequent starts or longer drain intervals.

In the end, the decision of which brand to use often comes down to experience.

If you are really looking for something different, and you aren’t afraid to spend more money, you might consider a synthetic engine oil. While conventional lubricants are distilled from crude oil in refineries, most synthetics are manufactured, or “synthesized,” by reacting components to make the desired product, in chemical plants. Some examples are poly-alpha-olefins, diesters, polyol esters, and silicone fluids.

In formulated products, synthetic base fluids offer use over wide temperature ranges; good stability; long service life and unique performance traits.

But while synthetics do have some advantages over conventional lubricants, it is important to match the correct fluid with the application for the best results. For example, synthetic oils can be the perfect choice for heavy-load applications and steep operating grades. While some people believe synthetic oils deliver extended drain intervals and protect engine components better, Falconer says expert opinion differs on the subject.

Even when the lube industry gets a handle on the PC-9 standard, Smyth points out that the EPA has made it clear it won’t stop there. Yet another – even-lower – emission standard, PC-10, is in the works for 2006.

“The industry had been put on notice by the EPA; we are in an era of constant change,” Smyth says.

“We are going to see gas technology move over into diesel engines with things like catalytic converters and particulate traps. And once we have those completely new engines, we are going to have to create a completely new lube for them.” n


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