GM
Engineer States that Oil Change Intervals Average 8,500 Miles with
Oil Life Monitors
By Nancy DeMarco
Typical drain intervals with General Motors’ Oil
Life System, the onboard computer algorithm that tells drivers when
it’s time to change their motor oil, are8,500 miles, versus 5,000
for GM’s competitors, a GM executive told last week’s World
Tribology Congress. Drain intervals over 30,000 miles are achievable
with minor engine modifications and appropriate oil quality.
“We cannot say exactly when it will happen, but
drain intervals will be lengthened,” James A. Spearot, director of
GM’s Chemical & Environmental Sciences Laboratory in Warren, Mich.,
told the World Tribology Congress meeting in Washington, D.C. Sept.
15. And itwill happen, along with numerous other technological
advances, thanks to the contributions of tribology – the science of
rubbing surfaces.
“Tribology is on the cusp of a renaissance,” Spearot said,
“triggered by the increasingly competitive manufacturing environment
around the world.” Manufacturing enterprises must have efficient
production, and they must produce products that customers want and
need. Tribology affects both.
Using the auto industry as a case study, Spearot
introduced some of the tribological challenges the GM Research and
Development Center is tackling.
“The auto industry doesn’t sell cars and trucks,”
said Spearot, “what we really sell is ‘automobility,’ the freedom to
move around at will.” Vehicle sales, which offer accessibility and
personal freedom, relate directly to personal income, he continued.
In 2000, 12 percent of the world’s population had
personal transportation, and Spearot projected this will reach 15 to
16 percent by 2020. “But,” he cautioned, “there will be societal
impacts.”
These challenges
include energy (where will it come from?), environmental
degradation, safety, congestion (“a very difficult challenge,” said
Spearot), and affordability. In almost every case, potential
solutions rely in part on tribology. Advanced propulsion systems
andadvanced materials will address energy and environ-mental
concerns. Vehicle electronic controls and soft-ware will mean more
safety. Agile manufacturing techniques will contribute to
affordability. Telematics mighttell drivers how to avoid congestion.
Quick plastic forming (QPF) of
aluminum is the first example Spearot cited in the area of using
tribology to improve manufacturing productivity and environmental
compliance. Automakers want to take the weight out of vehicles,
Spearot noted, and this GM process allowsthe company to form complex
parts from light weight aluminum and magnesium alloys. “Check out
the Chevrolet Malibu Maxx Lift Gate,” he said. “It’s made by this
process.”
Tribology is
essential to the entire medium-temperature(500 degree C) QPF
process. The surface quality of the die is critical, and microscopic
galling is an issue. In addition, “we’re still looking for a good
laboratory wear test to make friction measurements for the process,”
said Spearot. “Current tests do not accurately measure deformation.”
Lubrication is also critical to the QPF process,
reducing the coefficient of friction, improving formability,
increasing die life and reducing forming cycle time, among other
functions, but irregular lube application can deform the finished
piece, Spearot said. GM has looked at boron nitride lubricants,
which are “good but expensive,” and at graphite, which is “good and
cheap-er, but has clean ability issues.” And both lubricant shave to
be removed after the process.
Turning to tribology in product performance and
durability, Spearot noted that GM now uses light weight aluminum
engine blocks with cast-iron liners. The challenge is to replace the
cast-iron liners, he said. His researchers are looking at new
alloys, such as high silicon-content aluminum alloys, and they have
tried spraying an iron coating into the engine cylinders, but the
process isn’t resolved yet. “We still need to better understand the
wear surfaces.”
Extending oil drain intervals
is another area of product performance and durability, driven by
customer demand, environmental benefits, and increased warranty
protection. GM is concerned, Spearot noted, about the “uncertainty
of service-fill oils.”
Major drain interval improvements are achievable
with appropriate oil quality and hardware technology, to over 30,000
miles with minor engine modifications and over 40,000 miles with
major engine modifications, he added. “But we still need to strive
for the best fuel economy, no compromise on engine durability, and
no negative impact on emissions systems.”
GM’s goal in every application is to increase
lubricant life. The new Dexron-VI trademarked automatic
trans-mission fluids for all applications worldwide will be
fill-for-life, Spearot said, adding that “‘life’ will be defined as
perhaps 100,000 or 150,000 miles.”
Looking ahead, said Spearot, GM is studying advanced
materials and tribological systems. One key goal is to develop
“self-healing” tribological surfaces based on shape-memory materials
such as nickel-titanium alloys, for recovery of scratches.
In every application, Spearot concluded, “the
correlation between bench tests and performance is a critical
requirement. [The automotive industry] needs a fundamental
understanding of mechanisms and predictive models to guide materials
development.” Tribology is indeed the critical enabler for improved
efficiency, productivity and performance.
