Is knocking harmful?
Occasional light knocking won't harm your engines, and doesn't indicate a need for higher octane. But don't ignore severe knocking. A heavy or persistent knock can lead to engine damage.
IMHO, the knocking does not harm today's engines (due to better design than old ones), however, unthoroughly burnt exhaust would harm your CAT(cat. converter) and gradually shorten its life.
Come to think of it, most cars either recommend 87 or 91, who is buying 89 octane anyway?!
In some other countries, the rating system is different (not (R+M)/2). Their 91 could be our 87 here. Their 97 is close to our 91. Make sure you know that when you travel abroad.
Occasional light knocking won't harm your engines, and doesn't indicate a need for higher octane. But don't ignore severe knocking. A heavy or persistent knock can lead to engine damage.
IMHO, the knocking does not harm today's engines (due to better design than old ones), however, unthoroughly burnt exhaust would harm your CAT(cat. converter) and gradually shorten its life.
Come to think of it, most cars either recommend 87 or 91, who is buying 89 octane anyway?!
In some other countries, the rating system is different (not (R+M)/2). Their 91 could be our 87 here. Their 97 is close to our 91. Make sure you know that when you travel abroad.
