Over the years, synthetic oils have come with some strong claims about extended drain intervals and fuel savings but high price tags. The investment was considered worthwhile provided a fleet was on e...
Over the years, synthetic oils have come with some strong claims about extended drain intervals and fuel savings but high price tags. The investment was considered worthwhile provided a fleet was on extended drain intervals and didn’t have to drain the costly lube.
But significant improvements in the performance of the lower-priced mineral lubes combined with a drop in the price of synthetics is making for a raging debate over lube economics. So intense is the debate that lawsuits have arisen over specific mileage numbers on labels. Even the word “synthetic” is in dispute. Manufacturers of modern, highly refined mineral oils have argued in court that their processes involve a degree of synthesis, justifying the term synthetic.
In the North American market, API Group III base stocks and poly-alphaolefins base stocks [Group IV] can both be classified as synthetics. But according to some in the industry, such as Clinton Smith, Senior Technical Associate at Imperial Oil, “the term ‘synthetic’ has become basically a marketing term.”
Yet fleet operators continually squeezed by economic pressures to reduce their operating costs require maximum fuel economy and extended oil drains while still maintaining high engine durability standards. They need to cut through the marketing spin and understand the following competing claims, for example:
On the one hand, Jim Abram, Category Manager for Commercial Transport Lubricants at PetroCanada says, “Our full synthetic heavy duty engine oil can extend drain times up to 4 times longer than a non-synthetic 15W40 oil.” He points to real-world examples such as a bus fleet that extended its drain intervals from 12,000 km to 20,000 km with the Duron synthetic (a Group III product) and a construction fleet that extended drains from 250 hours to 900 hours.
On the other hand, Tom Keogh, Product Manager, Lubricants at Shell Canada, says, “If you’ve got a synthetic base oil in [the engine] it does provide some other properties, but quite honestly, it doesn’t allow you to extend the drain very much. I know there’s a lot of people out there promoting the idea that you can extend the drain to X number of miles or 3 times the normal oil and so on, but that ‘s not really true. It’s not true at all.”
At the heart of these claims is a number of issues: what categories of oil are being compared, in what application and what do recent tests say about Group II base stocks with superior additive packages? A basic understanding of how lubricants are made and grouped is useful here.
Since 1990, the American Petroleum Institute (API) has categorized oils in terms of saturate, sulfur and the viscosity index (V.I.). Saturate levels refer to how ordered the hydrocarbon molecule is. Simply put, a saturated oil is highly ordered – the carbon atoms are connected by single bonds. An unsaturated oil has some double bonds between carbons. Double bonds are undesirable because they can crack open, leaving a single bond, but creating a new bond to a foreign molecule, thus introducing chemical impurity to the oil.
Sulfur is a naturally occurring impurity in unsaturated mineral oil, which further refining can remove. The V.I. is a measure of viscosity with temperature. An oil with a high V.I. flows better in cold temperatures and will thin out less at high temperatures.
So a Group I base oil is solvent refined with saturate levels of about 75% and high levels of aromatics – approaching 25%. The aromatics component is responsible for oil deterioration due to oxidation, which results in oil thickening and poor soot dispersion. Group I oils have a sulfur content of more than .03% and a V.I. rating of between 80 -120.
The introduction of hydroprocessing in the mid-1980s, has significantly reduced the aromatics levels in Group II base stocks. Sulfur content in this group is less than .03% and saturate levels are greater than 90% – some are as high as 99%. Their V.I. rating is also 80 – 120. When the V.I. rating is pushed above 120, the oil is bumped up into Group III. Group IV stocks are poly-alfphaolefins (PAOs) synthetics. Each level of refinement adds cost to the oil.
“One of the things a lot of people don’t understand,” says Gary Parsons, Global Consumer & Transport Segment Director with ChevronTexaco “is synthetic lubricants also come from crude oil. One of the reasons synthetics are expensive is because you take crude oil, you refine it, then you separate it into well-defined chemical streams. You then take those chemical streams and make a synthetic base stock. So it’s a more laborious process.”
According to an SAE paper (2000-01-1993) presented in 2000 the extra effort is well worth it. The paper states that fuel savings with synthetics are well documented adding that a 5W-40 synthetic delivers a 3% economy enhancement over 15W-40 mineral oil with both lubricants fresh. It also stated that even a synthetic loaded with 7.3% soot still outperforms fresh mineral oil.
But others claim that semi-synthetics and some Group II oils have closed the performance gap considerably. “We’ve got blends that are about 20% synthetic. We’ve set our targets on low temperature viscosity. To meet that, we put in as little synthetic as we have to, but we have to put in some to meet those targets. Once we meet the target we’re happy,” says Keogh.The bigger question, of course, is whether Group II oils with superior additive packages can perform comparably to more expensive full synthetic oils in terms of fuel efficiency and extended drain intervals.
“We’ve written an SAE paper called Lubricants that Optimize Diesel Engine Fuel Economy and Allow Extended Oil Drains,” says Parsons. “In this, we’ve done field testing and controlled laboratory testing looking at the performance as far as wear, engine durability and fuel economy and extended drain intervals, comparing our multi-grade – which is a group II product – to a leading synthetic product. In this testing, we have statistically shown that there’s no benefit to a synthetic.”
SAE Technical Paper 2001-01-1968, presented to the International Spring Fuels & Lubricants Meeting & Exposition in 2001, gave a detailed account of tests on the following engines: a 1995 Caterpillar 3406E, a 1996 Detroit Diesel Series 60, and a 1999 Cummins N-14. It concluded that “premium additive packages using API Group II base stocks at > 99% saturate levels can equal synthetic oils in fuel economy and extended oil drain capability.”
“What was interesting was that in the audience you had all the major manufacturers of synthetic oils, but nobody challenged these results,” says Parsons. Then he adds that “we’ve done the same thing in gear and transmission lubricants. There, Eaton has a specification that dictates the use of a PAO synthetic – the Eaton Road Ranger fluid… This last September we tore down the trucks [filled with our Group II borate additive oil] at 750,000 miles without any drain. We’ve been able to pass all of the Eaton tests as far as wear control, visual ratings – all of that. We don’t meet some of the chemical requirements they’ve set, which is around the PAO, so we don’t have the full 500,000 mile approval yet… To be honest, they sell their Eaton Road Ranger fluid, so there may be some competitive interest there.”
In the essentially closed systems of gear boxes and final drives, synthetics make a lot of sense. Manufacturer warranties support their use. Drain intervals are up to 500,000 miles. They perform better at low temperatures and offer better protection at the higher temperatures modern truck aerodynamics impose on drivetrains. But when it comes to extended engine oil drain intervals, at least three of the major formulators refrain from making specific recommendations.
Smith of Imperial Oil is typical in this respect: “What we basically say is that you use the OEM recommendation as a starting point. If you want to extend the drain you do that with used oil analysis. You monitor things like wear, soot, etc.”
Or Parsons: “Our [multi grade] meets all of the extended drain intervals of the most severe industry standards… We’ve had customers go out
to 60,000 miles. We’ve had customers go beyond that. What we recommend is doing used oil analysis regardless of what product they use to establish what is a good drain interval.”
The problem with making specific extended drain recommendations for engine oils is that a crankcase is essentially an open system. The combustion process continually introduces contaminants into the oil. That contamination can show up in various forms. In a heavy duty diesel engine, blow-by and the carbon scraped off the cylinder liner enters the oil as soot.
“We’ve tested up to 9% soot in crankcase engine oil. At that level you’ve got 11 gallons of oil, but a gallon of that is soot you’re dispersing,” says Parsons. And with increasingly stringent emission standards requiring retarded ignition timing and exhaust gas recirculation, soot is likely to become an even bigger issue in the future.
Other contaminants from the combustion gases are acids, particularly from the sulfur in the diesel – which forms sulfuric acids. If a truck has a faulty injector or is subject to a lot of cold starting, some of the injected fuel gets into the oil. There can also be contaminants from mechanical problems – coolant from a leaking gasket, for example.
So the type of truck, its condition, the severity of use, climatic conditions – all these make specific drain interval claims a bit of a minefield. In fact, formulators that sell mineral oil stocks and synthetic oils are the least bullish on synthetics. Smith: “A synthetic oil’s ability to deal with soot is really driven by the additives. The oil itself is still a hydrocarbon oil.”
So how does Petro Canada justify its claim? First, it should be noted that its synthetic is a Grade III mineral base stock – and enjoys a price advantage over a POA stock. Abram also says that “Our base oils are 99.9% pure. They’re as clear as water… When you put the base oil through our hydrocracker and hydrotreater, you get that clear base oil.”
It should also be noted that when Abrams says “our full synthetic heavy duty engine oil can extend drain times up to 4 times longer than a non-synthetic 15W40 oil,” he is stating his company’s findings on the basis of “testimonials that support that claim.” Secondly, by “a non-synthetic 15W40,” he means a “Group I mineral oil.”
But why are manufacturers of POA synthetics not more eager to push their products?
Parsons: ” We have synthetics in our line and we’re happy to sell them. But we believe the cost performance of the Group II product is superior. People are getting better value for their money. In the long term, that’s the right thing to do.”
What the lube economics debate has brought to light is that fleets looking for savings now have several options. Which option is the best fit should be determined by careful examination of the fleet’s service applications and objectives.