Applications and Innovations
| March 01, 2011 |
R Synthetics 4 You?
By John Latta and John Baxter
Synthetic oils: They cost more, right? Well, yes, if you define “cost” as an upfront outlay. But a lifecycle cost analysis, or even a time-specific analysis – winter, for example – might convince you that under the appropriate circumstances, they more than pay for themselves.
Synthetic oil base stocks enable refiners to create engine oils with “better thermal stability,” says Maria Burcham, a technical advisor with ExxonMobil. Thermal stability is critical in keeping oil viscosity high enough for proper component protection.
At the extreme cold or extreme hot ends of the workday temperature scale, synthetics are out-performing mineral oils by losing less of their midrange structure.
“Synthetics offer both superior low-temperature performance and a high level of film strength at high temperatures to better protect all moving parts,” says Dan Arcy, a technical manager at Shell Lubricants. The fluid will be thin enough to flow easily and quickly, and reach all parts when you start up on a cold morning, yet it will remain more than thick enough when running at high speeds on a hot day.
While they are every bit as thick or “viscous” at normal operating temperatures as mineral lube, synthetics will start out thinner when you fire up equipment on a cold morning, says Baxter.
Almost all the oil ends up in the crankcase when the engine sits overnight. When the weather is cold, and at its coldest in the morning when you start work, synthetic oil pumps more quickly and circulates more freely. Also, wear surfaces will be lubricated more quickly with a lower-viscosity oil, and wear will be reduced
“We have a very cold winter now so, for example, there could be benefits to having city trucks with plows run synthetics,” says Arcy. “You get low-temperature pumpability and performance, and also ease and startability. Think what happens if several plows were delayed because they had starting problems, because oil was too thick and it was too cold. That’s costly to the community a number of ways.”
And there are incidental cold-weather costs.
“Cranking a cold engine puts more of a toll on the battery and starter, so there is some advantage there in using an easier-starting synthetic,” says Arcy. “We’ve done testing in cold temps to show how much battery power was needed to start an engine, and it’s significantly less with synthetics.”
The Contamination Problem
In environments where there is a ton of dust getting into the lube, synthetics sometimes lose their edge and may well need to be changed just as often as mineral lubes. It’s the contamination that ruins them and not breakdown. Here we go back to balancing cost and performance.
Any contamination is a threat, and working in a contaminated environment is one circumstance where the use of mineral lubes in drivetrain components might be preferred. In such cases, inspect the lube daily and replace it as frequently as it gets dirty or diluted with a less-expensive mineral oil, says Shell’s Arcy.
“In 2008, Hurricane Ike did some serious damage in Galveston [Texas] and tore up beaches,” recalls Arcy. “They started to rebuild beaches, so they were trucking sand around, working on the shore with dumps that sometimes drove into seawater, with axles going under the water. In a case like that, if I were asked to recommend oils, I wouldn’t have recommended synthetics because that oil would be contaminated, and it doesn’t make sense to use them when they have to be changed constantly in a work environment.”
Research clearly shows that synthetics are ideally suited for use in transmissions and axles, where combustion byproducts are not part of the equation.
Arcy also notes the critical difference between transmission and axle lubes, and the importance of using the right one. Transmission gear teeth are generally flat and the gears sit directly across from one another. In a drive axle, the large running gear sits at the level of the wheel bearings, but the pinion gear that drives it is off-center and at 90 degrees. The gear teeth in the drive axle rub together much more. Your dealer can help your selection for these two distinct uses.
The Semi-Synthetics Situation
There are also semi-synthetics on the market. As the name suggests, they are products that fall categorically somewhere between a mineral oil and a full synthetic. Now, they are also subject to a new debate.
Chevron Lubricants says it recently conducted benchmark and field testing to determine how its premium conventional heavy-duty motor oil, Delo 400 LE SAE 15W-40, performed against other major oil companies’ semi-synthetics. Test results show, the company says, that Delo 400 LE with ISOSYN Technology was equal to, if not better than, leading semi-synthetics in industry-recognized tests in the areas of wear control, oxidation and deposit control.
“Most heavy-duty semi-synthetics are touted as having superior performance over conventional oils, but that’s largely a marketing effort to persuade customers that the addition of synthetic base oil to an engine oil formulation will deliver a higher level of protection to critical components, thus justifying the extra price,” says Len Badal, commercial sector manager, Chevron Lubricants. “The notion that a semi-synthetic or synthetic blend provides significant benefits over a product like our Delo 400 LE 15W-40 is a myth.” Based on the research and general information provided by several large heavy-duty OEMs, says Badal, the performance benefits of semi-synthetics versus premium formulated heavy-duty engine oils are marginal at best, and typically don’t justify the additional price a customer must pay for them.
Through bench testing, Chevron documented examples of the competitive semi-synthetic performance myths in multiple areas versus its premium formulated Delo 400 LE 15W-40. In these tests, the Delo 400 LE with ISOSYN Technology performed equal to or better than many leading semi-synthetics. In one test designed to look at soot-related wear protection, Delo 400 LE significantly outperformed three of the four semi-synthetics tested, showing between 16- and 41-percent better wear protection in this test. Tests for oxidation and deposit control also showed very good performance results of Delo 400 LE versus the four major oil companies’ semi-synthetic products.
The company also conducted extended drain field tests on a dozen 15-liter Detroit Diesel DD15 engines. In these tests, Chevron claims to have extended drains out to 70,000 miles without filter changes, achieving the long drain intervals normally touted as a benefit of semi-synthetic products. According to the company, one engine was torn down and inspected at 400,000 miles and showed excellent durability and low wear.
Fuel Economy, Too
While fuel economy is not the key metric in transportation construction that it is in long-haul trucks, evidence from the trucking industry suggests synthetics could help construction fleet trucks that run up miles.
Peter Thomson, director of commercial and industrial marketing at Valvoline, notes that, “in addition to oxidative stability and low/high temperature performance, Valvoline has statistically-significant tests conducted by a leading independent laboratory that found fuel economy benefits for on-highway Class 8 trucks – up to three-percent maximum improvement in fuel economy using SAE J1321/TMC RMP 1103, Type II techniques.” Valvoline, says Thomson, “guarantees a minimum of 1.6-percent fuel saving, compared to traditional lubricants, when using our SmartWay accredited synthetic engine and axle oils, Premium Blue Extreme and Syn Gard FE in on-highway applications.”
Shell’s Arcy agrees that on-highway mpg advantages are proven, but there is no data to quantify off-highway miles per gallon advantages of synthetics. “I would anticipate that there’s a benefit there, but I don’t have the data. You see it on-highway, so why wouldn’t you see it off highway?”
Can You Swap Out?
It’s a commonly-asked question: Can you switch from mineral to synthetic? Shell’s Dan Arcy says it’s also one of the great myths that goes back and forth. For example, some customers use mineral oil in summer months and go into the synthetics for the winter months. “You can go back and forth without any issues. It’s a myth. Years ago, there used to be some issues, but now with seal compatibility there is no issue.”
What Are We Talking About?
So, what exactly are synthetics oils?
Valvoline executives point out that there are three categories of base oils that can be given the term:
Group III, which is highly-refined, hydroprocessed mineral oil,
Group IV, Polyalphaolefins or PAO, which is an engineered hydrocarbon-based product derived from natural gas, and
Group V, which are Esters, considered more applicable in industrial lubricants.
All offer chemically-stable and chemically-consistent base oils with high levels of oxidative resistance.
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