I run 87 in my m112 and I can’t tell any difference in power or mileage Sent from my iPhone
> On Sep 29, 2023, at 5:27 PM, Bob Rentfro via Mercedes <mercedes@okiebenz.com> > wrote: > > A car guy friend posted this about knock sensors and octane #s. Will this > make us all run out and burn 87 in our 91 only cars? > > “Short story on knock sensors: All modern cars have them. And because of > knock sensors, you can run 87 octane in a vehicle that says you have to run > premium*. > > Long story on knock sensors: Let’s start with gasoline. It typically comes in > 87, 89, 91, 92, 93 octane at the pump. Drag strips etc. often have even > higher octane. What is the difference between higher octane and lower octane? > Well, 87 octane will ignite at a lower pressure than 93 octane. So, with 93 > octane, you can compress the air (think turbo or supercharger) and have the > spark ignite sooner (timing advance) which creates more power. With 87 > octane, since it ignites at a lower pressure, high compression engines might > ignite the gas before the intake valve closes and you hear a noise (ping). > Often, in old cars, you will hear this pinging under load (moderate throttle > going uphill). What this noise is, is the detonation of the gas and air > mixture in your cylinders igniting before the intake valve is closed. The > explosion is partially sent into the intake causing the noise. What a knock > sensor does is detect this noise (the “pings” or “knocks”) and tells the > computer to spark/ignite at a slightly later time. > > *The only reason the manufacture tells you that you have to run premium fuel > if that the vehicle was tested for gas mileage with premium. Running premium > will get you slightly more power per molecule of fuel, thus better gas > mileage. If you run 87 octane, you might get slightly (and I mean slightly) > less gas mileage out of your vehicle. The manufacture doesn’t want to get > sued for advertising a certain MPG and you getting slightly less. They have > to tell you to run premium or risk litigation with the EPS or the consumer.” > > Accurate or BS? > > AZBob > > Sent from my iPhone > _______________________________________ > http://www.okiebenz.com > > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
