How Shell Rotella Measures Fuel Economy
Drivers and manufacturers alike are increasingly turning to engine oil to reduce CO2 emissions and deliver fuel-economy benefits. But how fuel economy savings are calculated is no easy task.
Today, the heavy-duty diesel engine industry and OEMs are increasingly looking to fuel economy to reduce carbon emissions.
Why? Because 22.4 pounds of CO2 are emitted with every gallon of diesel fuel burned1, so the less fuel a vehicle uses, the less CO2 it emits.
The growing demand for improved fuel economy has, in turn, driven the adoption of low-viscosity diesel engine oils. That the viscosity of a lubricant can contribute to an engine’s fuel economy is well known within the industry.
But it has taken nearly a decade for many operators to transition from heavier viscosity oils to thinner ones due to habit, apprehension about the performance and protection, and sometimes the cost.
In general, lower-viscosity oils reduce the amount of energy required to keep engine components in motion, which lowers fuel consumption.
For example, switching from an SAE 15W-40 oil to an SAE 5W-30 oil could provide significant efficiency gains. Lowering fuel consumption of course lowers fuel costs, however, even if fuel costs are not a concern for a fleet or driver, lowering CO2 emissions may be.
The focus on engine oil viscosity offers greater opportunities to realize fuel efficiency and therefore reduce the total cost of ownership through lubricant choice. However, it’s not enough to evaluate new engine oils in the laboratory: the true test is how they protect vehicles in real-life conditions.
Strengthened by a long history of investigating the effects of lubricant viscosity on fuel economy, Shell has developed a multi-year global fuel-economy field trial program – in real trucks, on the road.
The results help everyone understand these opportunities in realistic, achievable numbers (read on to discover what fuel economy savings certain Shell Rotella oils offer). And our program has shown that switching to low-viscosity engine oils could help operators and drivers achieve significant efficiency gains.
“Shell has accumulated more than 100 million miles in testing CK-4 and FA-4 type technologies, which show excellent engine protection in the field, even at low viscosities,” says Dan Arcy, Shell Global OEM Technical Manager, Heavy-Duty Diesel Engine Oil.
How we did it
Developing and testing new engine oils requires a careful balance: fuel economy must be balanced with product durability. And the precision of laboratory testing must be balanced with evaluating the oil’s performance in real-world conditions.
Consumers want to know that any performance benefits were tested and achieved under conditions that closely match their real operational conditions for the oil. However, evaluation in the field can be difficult because many factors influence real-world fuel economy, mainly driver behavior and driving conditions.
To isolate the effect of a lubricant, oil formulators conduct large-scale experiments that minimize the number of variables to be controlled, and standardize those variables that cannot be controlled. This approach eliminates bias and enables accurate evaluations of an oil's impact on fuel economy.
HERE’S A SUMMARY OF HOW SHELL TESTS OILS THROUGH OUR GLOBAL FUEL ECONOMY FIELD TRIAL PROGRAM.
Urban and highway driving conditions
How you drive can play a big role in your fuel economy. For example, trucks with different duty cycles, such as urban start–stop or high-speed, long-distance highway driving, will have different efficiencies.
Shell uses the Society of Automotive Engineers industry-standard drive cycles designed to reflect different driving environments: J1321 and J1526. The field trial is designed using these standards.
Statistics drive precision
Measurements are repeated and averaged, and the experiments carefully designed to minimize the variables that cannot be controlled, such as weather and humidity.
It’s important to isolate the impact of the lubricant itself. Shell’s experiments are run at certified independent test houses that regularly conduct closed-track experiments that simulate real-world driving conditions.
Comparing the right oils
Shell scientists tested six different development or prototype oils, including a reference CK-4 SAE 15W-40 oil and a prototype CK-4 SAE 5W-30 oil to understand their impact on fuel economy. Each truck saw each engine oil to ensure more accurate results.
Measuring fuel economy
Fuel consumption is measured by weighing the fuel tanks before and after each test run, and using electronic data loggers from the vehicle control unit. The fuel-economy benefit is calculated relative to a reference lubricant:
Fuel saved (%) = Average fuel used (ref. lubricant) ÷ Average fuel used (test lubricant) x 100
Average fuel used (ref. lubricant)
A wide range of engine manufacturers and types of technology are selected so that the results are representative of what customers experience in the market. In this case, six vehicles from different manufacturers were chosen. In addition, the vehicles are matched according to mileage and condition.
From REAL-WORLD FUEL ECONOMY, a technical paper by Shell, May 2019.
Accessible version of the Fuel Economy Infographic
Lubricant selection had a significant impact on fuel economy in real-world driving conditions.
The visual shows an infographic containing the following facts:
16,200km - distance covered in 12 days of testing. Thousands of kilometers covered in 12 days.
6 engine oils tested - from CK-4 SAE 15W-40 to prototype 0W-20 oils.
36 oil-truck - combinations run in repeat for a total of 72 oil-truck tests.
Independent - rest house qualified to run industry standard, heavy duty diesel, fuel economy tests.
5,544 data points collected - fuel economy measured by weighing the fuel tank before and after a test run and corroborated using real-time data.
576 fuel-economy tests - 8 tests per truck per day to evaluate urban and highway driving cycles.
6 vehicles tested - from different manufacturers including SCANIA, DAF, IVECO, MAN, DAIMLER and VOLVO.
The program results
The Shell heavy-duty diesel engine oil technology team applied the above approach to fuel economy field trials in North America, China and Europe between 2014 and 2017. The results showed that lubricant selection has a significant impact on fuel economy in real-world driving conditions.
For example, compared with a market reference SAE 15W-40 oil, an SAE 10W-30 API FA-4 type oil resulted in a statistically significant fuel-economy benefit of up to 2.6% over the combined urban cycles. In other words, switching to a low-viscosity Shell engine oil could lead to a substantial reduction in fuel costs over time.
“We believe Shell to be the first organization to conduct a fuel economy trial of this scale and complexity. At its heart is a drive for the Shell technology team to deliver credible results to our customers using their equipment,” says Dr Jason R. Brown, Shell Heavy-Duty Diesel Engine Oil Global Technology Manager.
We know that going to a lighter/lower viscosity product like our Shell Rotella® T5 10W-30 Synthetic Blend or Shell Rotella T6 Multi-Vehicle 5W-30 Full Synthetic can provide significant fuel economy benefits.
Which Shell Rotella products give better fuel economy?
Based on our extensive field trials
- 2.8% fuel economy saving2: Shell Rotella T6 Multi-Vehicle 5W-30 Full Synthetic Oil
- 2.6% fuel economy saving2: Shell Rotella T5 Ultra Synthetic blend 10W-30 (API FA-4) Oil
- 2% fuel economy saving2: Shell Rotella T5 10W-30 Synthetic Blend Oil
“It’s well known that fuel economy links to CO2 emissions, so even if saving money on fuel isn’t a top priority, becoming greener may be” says Shell Rotella Global Manger, Megan Pino.
“Drivers, fleet owners and manufacturers alike are increasingly turning to engine oil as a way to enable and deliver fuel economy benefits. And we expect this trend to keep growing.”
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