Old man at the Benz dealership says he’s been driving the same car for a long time and usually only puts in 87 octane in sprinkled with 91 every few times. What problems could this cause? Do I have to put in 91?
Disclaimer: I’ve owned (paid off) the car for 6 years and do put in 91, but trying to cut costs.
If you put in lower octane and it knocks, the computer will retard ignition timing to try and stop the knock. But there’s a limit to much it can do that. Also, knock detection is also reactive, after the fact, so you can have detonation and it can cause engine damage before the computer can stop it.
This right here. I’ve driven a few beat up panameras where the owners were clearly not spending money on them. They spark knock like crazy on a hot day when running 87. I’m sure the computer had the timing backed as far off as it could but there’s only so much range when it’s made for higher octane.