AS SEEN IN LUBES'N'GREASES
BY STEVE SWEDBERG
Fuel Economy,
Any Way You Can!
f you are like me, and
have a pickup truck or
an SUV, you know the
cold terror that runs
through your body as you
pull up to the gas pump at
your local “petrol purveyor.” Regular gasoline at $4
per gallon is your fate, or
even worse, you might
need mid-grade or premium. My truck has a 24-gallon tank which means that
if I wait until the last fumes
are burned, I’m looking at
$100 for a fill up.
I
What I thought might be
instructive is to take one
vehicle (my pickup is the
guinea pig) and see what
can be done to gain as
much fuel economy benefit
as possible. With that in
mind, let’s get started.
Engine Oil
My owner’s manual recommends SAE 5W-30 for yearround use. However, I wondered if something would
give me a bit more fuel
economy. To that end, I
spoke with Bob Olree,
development engineer,
materials engineering for
fuels and lubricants at
General Motors Powertrain
in Troy, Mich., about using
lower-viscosity engine oils.
Olree pointed out that my
owner’s manual also recommends SAE 0W-30 for colder climates. When specifically asked about SAE 0W-20,
he would not recommend
that grade for my truck —
but he did indicate that he
has confidence in the quality
of modern engine oils. (I
should note here that Olree
took me to task in a Letter
to the Editor in July’s issue
for my concerns about wear
protection with SAE 0W-20.)
Reading between the
lines, I think that I could use
SAE 0W-20 and not put my
engine at significant additional risk. Changing from
SAE 5W-30 to SAE 0W-20
should net me an additional
0.5 percent in fuel economy. That’s worth an additional one-tenth of a mile
per gallon at my current
estimated 20 mpg. Maybe
I’ll try it next winter.
Transmission Fluid
Automatic transmission
fluids have been very low
viscosity, friction-modified
fluids for some time. While
there are diverse and incremental changes going on in
the ATF area, no one has
quoted any fuel economy
benefits from the fluid
alone. There are some
rumors circulating that
improvements in fuel economy might be able to be
captured with advanced
ATF chemistry.
Transmission hardware
designs are changing to
provide better fuel economy, so think continuously
variable transmissions (CVT)
or double-clutch designs for
your next purchase.
If you have a manual
transmission you can possibly use a lower viscosity
lubricant. One recommendation is for an SAE 75W85 synthetic product meeting the API GL-4 specification. It may be possible to
go to an SAE 70W-85 and
perhaps capture a miniscule amount of additional
fuel savings. Many manual
transmissions are using
ATF too, which is probably
going to give maximum
© 2008, LNG PUBLISHING CO. REPRINTED WITH PERMISSION FROM THE SEPTEMBER 2008 ISSUE OF LUBES'N'GREASES MAGAZINE.
1
benefits for fuel economy.
However, before making
that change, read on
about gear lubricants.
Rear-axle Lubricants
The recommended axle
lubricant for my truck is
SAE 75W-90 synthetic
gear oil meeting GM
Specification 9986115. I
wondered if I could gain
from a gear lube of lower
viscosity (SAE 75W-85)
with improved chemistry.
Remembering that
Lubrizol had worked on
fuel-economy-enhancing
gear oils back in the
1980s, I contacted Paul
Lewis, the company’s
global automotive gear oil
additive product line manager, in Wickliffe, Ohio. I
asked whether or not any
new work had been done
to enhance fuel economy
via gear lubes.
Lewis and I discussed an
article on Lubrizol’s website about automotive gear
oils that raises “A Question
of Balance.” It points out
the basic conflict between
fuel economy benefits that
could be gained by going
to lower viscosities versus
the necessity of maintain-
ing and enhancing the
fluid’s impact on durability.
It is not difficult to claim
axle efficiencies can be
improved by reducing viscosity to minimize frictional churning losses.
However, light trucks and
SUVs are often used in
conditions that result in
high loads and high operating temperatures. In
addition, engine horsepower has increased by 34
percent over the last
decade, while axle sizes
have remained constant.
Sump capacities have
been reduced and drain
ENERGY LOSSES FOR VEHICLES
Urban Driving
Standby 17%
Fuel
Tank
100%
Aero 3%
Accessories 2%
13%
19%
Engine
Driveline
Rolling 4%
Engine loss 62%
Driveline Losses
6%
Braking 6%
Highway Driving
Standby 4%
Fuel
Tank
100%
20%
25%
Engine
Aero 11%
Accessories 2%
Driveline
Rolling 7%
Change More than Oil
Engine loss 69%
Driveline Losses
5%
Braking 2%
Source: US EPA
2
intervals lengthened.
The bottom line seems
to be that it has taken new
additive technologies to
maintain and enhance gear
durability, while lowering
the viscosity of the axle
lubricant for improved fuel
economy.
Lewis pointed out that
the durability vs. fuel economy question is one that
is of great interest to original equipment manufacturers. He also pointed out
that the industry is very
interested in developing a
standardized fuel economy
test for gear oils. Currently,
the various OEMs have
data and procedures they
use to characterize the
fuel economy benefits to
be gained from gear lubricants. Recently however,
the U.S. military
approached SAE with a
request to develop such a
test in conjunction with
SAE J2360, which is the
SAE standard for automotive gear oils (formerly
MIL-L-2105E). Although it’s
in the early stages of
development, any standard will likely cover fuel
economy for both passenger cars and commercial
vehicles.
As far as improving my
fuel economy by using a
lower viscosity gear lube
in my truck, it sounds as
though the benefits are
not really measurable and
the risks are too great to
take a chance at this time.
© 2008, LNG PUBLISHING CO. REPRINTED WITH PERMISSION FROM THE SEPTEMBER 2008 ISSUE OF LUBES'N'GREASES MAGAZINE.
As I was writing this
article, GMC e-mailed its
Top 10 fuel saving tactics
to me. Just in case you
missed it, they are as
follows:
1. Go the speed limit.
Use cruise control.
2. Drive evenly. Avoid
hard stops.
3. Avoid idling and rushhour traffic.
4. Open windows at slow
speeds. Use air conditioning on highways.
5. Remove junk from the
trunk.
6. Fill up when it’s cool
and before holidays.
7. Don’t top off gasoline
and tighten the cap.
8. Use the correct fuel
grade.
9. Don’t accelerate uphill.
10. Avoid rooftop carriers.
For most of us, it’s hard
to avoid rush-hour traffic.
As far as driving habits are
concerned (e.g., speed and
road practices), most of us
grew up driving in better
times when “go, go, go”
was the norm. It seemed
as though we were always
in a hurry to get someplace. That hasn’t changed
very much. In my case, it
has required a great deal of
“re-training” and I’m still
learning.
Where I live in Arizona,
opening the windows in
lieu of air conditioning is
not a good idea in the
summer! Filling up when
it’s cool is also difficult in
these parts. In fact, there
has been a lot of discussion locally about what
should be the standard
temperature for weight-tovolume conversions for
fuel. As most of you know,
60 degrees F is the temperature selected a number of years ago as representative of the average
temperature across the
United States. Here in the
Phoenix area, 60 F is probably a bit low in the sum-
mer, but in the winter, it is
an advantage to the consumer. However, that’s a
subject for another article.
Some of GMC’s supplemental recommendations
are to change your oil to
the recommended grade,
make sure your fuel system is clean and functioning properly, inflate your
tires and keep them at the
proper pressure, etc. There
are literally dozens of other
suggestions for maximizing
fuel economy, and I recommend that anyone who is
interested just “surf the
web” to see what’s out
there. (Just remember to
be skeptical about what
you read.)
Stopping Losses
One area of interest is the
amount of energy lost
between the fuel coming in
and the vehicle moving
down the road. The EPA
has detailed the various
factors relating to energy
losses — from the engine
to the driveline and over
the road — for vehicles in
urban and highway modes.
(See chart on page 8.)
What is so amazing
about this analysis is the
variety and magnitude of
energy losses that occur.
No wonder the automakers
go nuts trying to squeeze
every bit of fuel economy
out of their fleets.
In the case of my truck, I
have never seriously considered investing in a bed
cover. After seeing that
there is an 11 percent loss
in efficiency due to aerodynamics at highway speeds,
I am now shopping for
something to streamline
the air flow over the vehicle. Even a snap-on tarp
could help. In fact, taking
the tailgate off will help by
allowing for smoother airflow over the truck’s body.
I’m not sure I can calculate
the impact of this aerodynamic fix but assuming
that half of my driving is
urban and half is highway,
the average impact of
aerodynamic losses would
appear to be 5.5 percent. If
I can cut that in half by
covering the truck bed, I
could perhaps capture 2
percent or 3 percent
improved fuel economy.
That’s about 0.5 mpg, or
another 12 miles per tank
full. Not much, but it is a
step in the right direction,
and five times what I’ll
gain from a lower-viscosity
engine oil.
Some of you regular
readers are probably saying about now, “What
happened to Steve’s view
that such small changes
will never be detected by
the average driver?” I
guess that even an old
curmudgeon like me can
see the light.
water solution to catalyze
combustion.
The EPA has looked at
over 100 of these devices
and has found that none
of them deliver on their
promise of improved fuel
economy. Popular
Mechanics tested a number of these devices and
got results similar to the
EPA findings.
So the bottom line to
fuel economy is to follow
a few guidelines:
1. Maintain your vehicle.
2. Make sure you use
the right lubricants for all
parts of the vehicle.
3. Use good driving practices.
4. Don’t bite on claims of
great improvements in fuel
economy by using add-on
devices.
Drive safely and economically. ❚
Gidgets and Gadgets
No discussion of fuel
economy would be complete without mentioning
the many (and I do mean
many) devices that are
offered to save gasoline.
They can be grouped as
either fuel-mixing or fuelmodifying devices. Some
purport to improve the
mixing of fuel and air by
creating turbulence in the
intake manifold. Some
claim to “align” the fuel
molecules for more complete combustion. Other
devices claim to convert
water to hydrogen and
others use platinum in a
Steve Swedberg has over
40 years experience in the
lubricants industry, most
notably with Pennzoil and
Chevron Oronite. He is a
longtime member of the
American Chemical Society
and SAE International,
where he was chairman
of Technical Committee 1
on automotive engine
oils. He can be reached at
[email protected]
© 2008, LNG PUBLISHING CO. REPRINTED WITH PERMISSION FROM THE SEPTEMBER 2008 ISSUE OF LUBES'N'GREASES MAGAZINE.
3