Start-stop systems are another engineering response to changing fuel economy and greenhouse gas regulations. American automakers are employing start-stop across their entire lines, although adoption trails that of automakers of European vehicles. Twenty-eight percent *of 2018 models in the US market came equipped with start-stop technology. And the number is expected to grow. Understanding what’s behind start-stop technology has never been so important.
* US Environmental Protection Agency, March 2019, Highlights of Automotive Trends Report, analysis of 13 large global auto manufacturers.
Performance and wear protection for 300,000 start-stops
Proving Mobil 1™ lubricant technology in the lab
ExxonMobil engineers study the lubricant technology of Mobil 1 oils through specialized start-stop testing – 300,000 start-stop cycles at a time. The engineers aim to create punishing real-world conditions as would occur during the life of the vehicle, which helps them accurately measure the performance and protection of Mobil 1 oils within start-stop systems.
After simulating driving 120,000 miles with extended oil drain intervals, which translates to about 80 daily start-stop cycles, ExxonMobil engineers determined that Mobil 1™ 5W-30 demonstrated excellent performance while providing wear protection under extreme start-stop operations.
Every stop saves: Conserving fuel with start-stop systems
Start-stop systems focus on conserving fuel in a relatively straightforward fashion. It’s all in the name: "Start-stop." For example, when you make a full stop in your car at a red light, your engine shuts down. Then, when the light turns green and you let off the brakes, your engine automatically starts back up in a few milliseconds. So, overall, the fuel economy benefits can be found at every full stop, using less gasoline by limiting the amount of time your engine idles.
However, it’s challenging to estimate what impact start-stop technology will have on mpg. For drivers with start-stop systems, there will be varying results toward fuel economy. In fact, the Environmental Protection Agency (EPA) fuel economy estimates do not factor start-stop into their mpg ratings. Factors like driving conditions and driving style can have a considerable impact on mpg. Many engineers estimate about 3 to 10 percent, which could add a couple mpg (e.g., 20 mpg in city driving improves to 22 mpg).
Meeting the demands of start-stop
Engines with start-stop systems endure more stress than engines without it. While the average driver may only experience about six to eight engine starts a day, the same driver with a start-stop engine could experience dozens. This increase in start-stop cycles affects several engine components – from the starter motor to the battery to the engine crankshaft.
Also, many different starters and batteries can support start-stop systems, but the internal combustion engine design remains the same, requiring enhanced protection from the extra loads on the crankshaft and rod bearings created by frequent start-stop cycles. Some automakers have even begun applying protective coatings on these bearings to address the potential for increased wear. Mobil 1™ advanced full synthetic motor oil is specially formulated to help reduce wear on these critical parts.