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.
It won’t have as much power and may knock
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.
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.
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.
If it’s newer and has active knock sensing/retard
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.
Using the wrong fuel does engine damage. If it is made for premium, and it is, then that is what you should be using.
The popular saying usually applies. “ The cheapest thing about a Mercedes is its owner”. Everyone is always running regular, getting $20 oil changes and almost always on the cheapest Chinese tires you can find. Just shows that they chose the wrong vehicle to own.
This is wrong with every vehicle, has nothing to do with the brand.
Throwaway’s statement is actually true: Even with knock sensors and ignition retard, you can still have detonation and engine damage. There’s a limit to how much the computer can retard spark
It can cause engine damage in certain extreme circumstances. The statement made was that it does cause engine damage which, in the context it was used, implies (a least to me) that you can’t even run 87 one time. Unless your car has an aftermarket tune, it’s likely not to have an issue.
My 2019 with GDI and turbo runs much better on 93 octane, even though the manual says that 87 can be used. On 87 engine lags and the transmission seems confused for what gear to be in, none of that happens with 93, ( 87 and 93 are the choices where I fuel up ).
Only used 93 premium even if the manual said to use 91 only
93 is not available everywhere hence mfg recommendations say 91+
91 is mainly available in higher elevations since 93 is not needed, so that 93 youre putting in does absolutely nothing, youre just paying extra out of pocket
same goes for econo shit boxes that you think is a race car because you put a 4" fart pipe and a weak ass looking high rise spoiler. if it requires 87, putting in 91+ wont make a difference in the world
On newer cars? Slightly less torque, slightly less fuel economy.
On older cars? Some pinging at high loads like towing or going up a steep incline.
On modified high performance turbocharged or supercharged cars? Catastrophic failure if pushed too hard too long.
This happened to me, not bad fuel but too much boost.
Ouch, too much boost is definitely trouble. The primary goal of the performance tuning process is slowly raising boost to within the limits of the engine durability, fuel system capacity, turbocharger limits, and fuel octane. Uncontrolled over boost can crack pistons, blow rods through blocks, and generally never end well.
My car isn’t modified but the manual says it will cause engine failure and override any form of factory warranty if 91+ isn’t used. Is this a hoax?
Reduced performance and economy. You’ll usually get better mpg with the recommended fuel so its best to keep using it. You might have some other small issues but it takes years of using the lower number to actually cause issues.
If it says REQUIRES 91, then you will have misfires, trouble starting, drastically reduced power and economy, and engine problems after a while
If you’re trying to cut costs, you could sell the car and get something more economical.
Everyone’s right about the minimum octane requirement as stated by the factory to mitigate knocking (bad) or a pull back in timing (resulting in no damage but lower performance).
However, there’s another advantage of using the highest octane fuel, which is cleaning additives. Fuels are pretty much generic, but additives are proprietary. The higher octane fuels generally have more of these proprietary additives, so using them can better ensure cleanliness within your engine.
If you want the additives in all octanes use TOP TIER FUEL.
100% agree. Here’s a link to Top Tier fuels.
You can also run a bottle of injector cleaner through it every few thousand miles and save the prices at the pump
I had an old Audi years ago that I really couldn’t afford to put 91 in. It ran like shit and would barely work with 87
My 2007 X3 doesn’t seem to care. Lots of other shit breaking but nothing related to fuel or pistons after 100000 km.
I think you can use 87 and put in octane booster into the tank, at least that’s what Scotty says anyway
stop thinking and listening to scotty
Don’t worry it’s just the engine…
The Computer scales back the timing (Can’t use the proper “R” word) when it detects detonation & you lose some performance.