United Kingdom & Ireland

Stop-start systems

Stop-start systems are another engineering response to changing fuel economy and greenhouse gas regulations. This technology is gaining popularity too with car makers, employing it across their entire lines. Understanding what’s behind stop-start technology has never been so important.


Proving Mobil 1 lubricant technology in the lab

ExxonMobil engineers study the lubricant technology of Mobil 1 oils through specialised stop-start testing – 300,000 stop-start 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 stop-start systems.

After simulating driving 120,000 miles with extended oil drain intervals, which translates to about 80 daily stop-start cycles, ExxonMobil engineers determined that Mobil 1™ 5W-30 demonstrated excellent performance while providing wear protection under extreme stop-start operations.

Every stop saves: Conserving fuel with stop-start systems

Stop-start systems focus on conserving fuel in a relatively straightforward fashion. For example, when your car stops 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 fuel by limiting the amount of time your engine idles.

However, it’s challenging to estimate what impact stop-start technology will have on mpg. For drivers with stop-start systems, there will be varying results toward fuel economy. In fact, the Environmental Protection Agency (EPA) fuel economy estimates does not factor stop-start into its 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 of mpg (e.g., 20 mpg in city driving improves to 22 mpg).

Meeting the demands of stop-start

Engines with stop-start systems endure more stress than engines without. While the average driver may only experience about six to eight engine starts a day, the same driver with a stop-start engine could experience dozens. This increase in stop-start cycles affects several engine components – from the starter motor to the battery to the engine crankshaft.

Also, many different starters and batteries can support stop-start 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 stop-start cycles. Some car makers 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.

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