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.
Basically nothing. Under hard acceleration though it’s not ideal. Cars designed for 91 usually run a bit more advanced with timing so a lower octane fuel would theoretically cause pinging. I doubt old man goes that hard though. Over the long term the engine might be a little dirtier with carbon buildup vs if they used 91 religiously. So yeah basically nothing. Oh and slightly poorer fuel economy.