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.
Just read the manual and find the octane section, and put in the minimum that is stated there. Many cars “recommend” premium/91+ for full performance, but that doesn’t mean they need it, they just benefit.
Some cars literally demand 91+ though. Not using it won’t be immediately fatal, but you may hear it pinging away during acceleration on a hot summer day. If it’s newer and has active knock sensing/retard it will just be working overtime constantly, which isn’t ideal for the long term engine life.
My 1980 Dodge had that. Never heard a ping from it. But that doesn’t change the fact that the car itself was junk, a perfect example of why Chrysler almost went out of business. Bumper to bumper failures and defects.
An engine that requires premium has to use premium. They have higher compression and will constantly ping no matter what causing severe engine damage. The severe engine damage comes from two flame fronts. One from the fuel self ignition g like a diesel running into the fuel which is igniting due to spark. If you don’t run the right fuel your gas engine essentially runs Iike a diesel which causes pretty quick and catastrophic damage.
This is assuming there’s no active knock sensing and timing control, which is unlikely on anything made in the last 15-20 years, especially if it requires premium. The manufacturers learned that people are often stupid, and mistakes happen. So a tank of low grade here or there can be accounted for. But if you use it constantly while beating on the engine, yeah, damage will add up over time if you exit the bounds of what the computer can adjust for.
The computer can either adjust for it or it can’t. Knock sensors have been in cars for much longer then that. Once again knocking is the fuel igniting before spark and after spark. You can still have ignition events occur after spark has occurred.
Use the right fuel period.