DarkJediKnight
Member
Can someone explain to me the purpose of 89 octane? It seems your common gasoline car runs on either 87 or 91. Why does 89 exist? Is it an in-between gas for premium users? Makes 87 users drive smoother? I don't know.
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89 Octane Gas: The Middle Child no one wants?
- Thread starter DarkJediKnight
- Start date
Its sometimes the only option in rural spots where they might not have 91. Also generally a 91 car will be fine if you put 89 in it if somewhere is charging way too much for 91.
Octane preference isn't as set as that. A car that ask for premium will run on a lower octane gas but the ECU will retard timing to prevent engine knock. Most of the time(100% of the time) this means less power and worse gas mileage. Also 91 isn't always available in some areas and 89 is a close substitute.
I've always been told that they are measured differently. Let me look up a source.
Edit: https://youtu.be/cfhTTuxF6Mk
I've always been told that they are measured differently. Let me look up a source.
Edit: https://youtu.be/cfhTTuxF6Mk
You're right.
This explains it pretty well.
https://www.etuners.gr/fuel/
Just saw that you found it first.
It's a different way of measuring and closer in real value, but generally European gas is slightly better refined. Doesn't matter a lot though, since putting higher octane in an engine that doesn't need it won't do much for normal traffic. You just need a high octane to prevent knocking (unwanted ignition of the fuel in the cilinder) at high (compression) speeds. Many modern car nowadays have better knocking sensors and can compensate for the fuel injected, but older cars can have erratic behaviour at high speeds if the octane is low.
The mid-octanes are all mixed at the pump (from two main tanks) anyway.
ChainedMaster
Banned
Can someone explain if I'm correct here please. My car is recommended for 91 octane. What I like to do is put half 93 and half 89 octane. Does that equal 91 octane? Does octane work that way that you can add them and divide the rating by two?
SMOK3Y
Generous Member
Why not just use 93?
Just put in 93 and make it simple.
ChainedMaster
Banned
Not necessarily. Octane is a number that says how unlikely it is that a mixture of fuel will experience unwanted ingnition compared to a specific fuel. Mixing two mixtures will not gaurantee the new mixture number is exactly the average of the two mixtures and can even have a worse number (although that will likely never happen). It's best to use all fuel above the recommended rating if you want to keep good engine performance and durability.
Subpar Scrub
Banned
Yep. I usually run 95 minimum in any car I own and 98 in my bike.
The only issue I've experienced is that 91 fuel is generally less refined here. Almost every car I see at work that needs a new fuel filter or pump (before the expected replacement date) was run exlusively on 91 and the parts are gunked to all shit.
Also, never run a car or bike under the quarter tank mark if you can help it, people.
Petrol/diesel/LPG are standard types of fuel. Usually, petrol come in variants with different octane levels. I've never really seen diesel have a non-standard variant. Never owned an LPG vehicle.
zorlaczerohero
Banned
Yeah, though my local station has changed to 91e/94e/98 for some reason. Means I have to use 98 in my wife's car and my fucking mower because neither will take ethanol.
Define high-end.
Basically. Unless your car specifically says it requires higher octane using does nothing.
David Incorporated Esq.
Member
Because I'm a cheap shit. I need to get me one of these pumps:
Just use 93, the amount of money you're saving is negligible.
It's based on engine design. Some cars that are sub-20k still require premium, but for cars that don't you'll see no benefit using higher octanes.
A little more explanation. Some engines compress the fuel/air mixture more prior to combustion to make more power or get better efficiency, and lower octane fuels might spontaneously ignite or burn too fast for a controlled burn in an engine like that causing damage. Higher octanes are better at resisting spontaneous ignition, so the fuel/air mix can be compressed more before ignition.
Nope. High compression engines (this applies to many modern cars in many price ranges and just about anything turbocharged) benefit from using higher octane. Most modern cars wont stop working if you give it gas with too low an octane rating but it will hurt performance and reliability.
This isnt strictly true. Many cars can adjust timing if you use higher octane and performance improves.
^ Interesting... I'm curious why I know so little about this kind of thing. I love cars and I love mine, but I've never even checked the manual to see what kind of gas it wants. I have always bought the cheap shit (even for my motorcycle) and it's always worked just fine.
"High end" I guess - I'm not really talking about hypercars or anything over $500k, in which it's obvious why you'd use a high octane fuel.
Just when I see the guy at Costco putting high octane fuel in entry-level BMW or Audi or whatever it makes me roll my eyes a little. It's always seemed like an idiot tax to me.
Like luxury cars that will run you $100k or more.
"High end" I guess - I'm not really talking about hypercars or anything over $500k, in which it's obvious why you'd use a high octane fuel.
Just when I see the guy at Costco putting high octane fuel in entry-level BMW or Audi or whatever it makes me roll my eyes a little. It's always seemed like an idiot tax to me.
Thaedolus
Gold Member
It has more to do with compression ratio of the engine, Im reasonably sure. You need a more stable fuel for higher compression or itll cause detonation (engine knock). Higher performance motors tend to have higher compression ratios.
Just use whatever the manual says to use. Youll see no benefits if your car calls for 87 and you use 91. That said, if you use a lower octane than called for, you could be causing additional wear on the engine.
Those cars will almost certainly perform best with the highest octane fuel and probably require it.
My 07 328i asked for 91 or higher. Wish we had 93 here in CA though cause my turbo 135i would appreciate it so much.
No, there are cars much less costly that benefit from higher octane. A lot of power cars do. Now, a Chevy Impala or a Kia Soul? Not so much.
David Incorporated Esq.
Member
Fair enough, I always forget some cars now will advance ignition, not just retard.
I had a 3 series and putting in 89 would give me worst mileage that completely cancelled out the cost savings in getting 89 over 91. Made the car noticeably slower too.
But Ive also had a Acura TL and using 89 only made it a bit slower and mileage was only slightly worse.
Guess it all depends on the car.
sixteen-bit
Member
When there are gas shortages it seem like the last one to go
peteykirch
Member
Here in NJ, Sunoco is the only place that offers 93.
Miss when they used to have 94 Octane.
Miss when they used to have 94 Octane.
David Incorporated Esq.
Member
Yeah it has nothing to do with the value of the car and if you're going to judge people for using it when you don't know why it's needed or not is rather ignorant.
Agent_ShortBus
Member
They don't need to be high end. My 350z only takes 91 and it's not an expensive car it's probably just because it's a sports car. You should really check your manual or gas cap and make sure you're using the right mix. Rather have to pay a couple more cents a gallon then have engine trouble later down the road to save money. Always pumping 91 I kinda don't even look at pump prices since I'll almost always be paying around $3.25+ a gallon. Also lol at the part where you love cars and your car but don't even know what it's supposed to run on. I'm guessing you also don't change your own oil or brakes....
Mammoth Jones
Member
My Grand Cherokee 5.7 Hemi recommends 87. So that's what I've always used. Worth it. I love that v8 engine so much.
Gonna take my baby to the car wash.
Gonna take my baby to the car wash.
Yeah, I have an X5 that also says 91 or better inside the gas door. I do notice better mileage when I use 93 vs the occasional 89. The price difference is like $2 per tank so it makes no sense why I choose to cheap out occasionally. The costco membership helps, their 93 is usually much less expensive than other places..... I need to stop with the 89. Haha.
whatsinaname
Member
Uh huh.
Nope, pretty much any German car or anything with a turbo performance, mpg, and reliability of the car over time will suffer if youre putting 87 in there.
David Incorporated Esq.
Member
^^^ You don't need to make stereotypes based on poor understanding of engine operation, the manual will tell you.
And why bother looking at the price? Are you not going to drive your car? I mean you might decide not to go on a long trip, but are you going to stop going to work?
People seriously over-react to variations in fuel price. I'm not saying you don't notice an increase of $2 to $3 per gallon, but price hunting from station to station for a five cent difference is asinine.
And why bother looking at the price? Are you not going to drive your car? I mean you might decide not to go on a long trip, but are you going to stop going to work?
People seriously over-react to variations in fuel price. I'm not saying you don't notice an increase of $2 to $3 per gallon, but price hunting from station to station for a five cent difference is asinine.
SMOK3Y
Generous Member
I think there's even Diesel & Diesel Super now lol
Ya I've used 98 in everything for yrs now I even find my whipper snipper runs smoother on it
whatsinaname
Member
When I first started driving, I used to map out my routes to include the less expensive stations on the route without too many detours. After 6 months of that, I switched to the station that was easiest to enter and exit...
Mammoth Jones
Member
Shit ads up. Fuck that. I mean there two two gas stations next to each other. 50c difference in price. I don't know how that sunoco stays open. But I absolutely would go somewhere else for 5c cheaper gas. Add that up over a year.
My car says to use premium and as far as I can tell it makes no difference to either performance or fuel consumption
jongkookie
Member
Yup.
Most Beemers need 91 in order to get the best performance and gas mileage. You could definitely put in 87 in it and for a regular person they wont notice it unless the car is about to break lol.
That said, if you drive a car that requires 91 and you dont put in 91, then I also think youre an idiot because you clearly cant afford the car if youre skimping out on gas.
My understanding is that gas mileage is better when you use premium if your car is designed to use premium as the engine doesn't have to strain as much.
whatsinaname
Member
Here's an article from a Ford engineer about using lower than recommended rating gas.
http://oppositelock.kinja.com/the-real-impact-of-using-wrong-fuel-octane-1785829176
http://oppositelock.kinja.com/the-real-impact-of-using-wrong-fuel-octane-1785829176
Yeah I will put in 89 when they are charging a 50 cent + premium for 91 which is actually pretty common here in MN. At that point the savings are worth losing a bit of mpg and performance from time to time. Super America does 10cents off 91 so generally thats my go to but if Im in a weird spot or on a trip and the 91 is over $3 and the 89 is like $2.50 Ill go with the 89. The shell app is also nice with near constant T-Mobile discounts but the issue is there are hardly any shells here.
^^^^ yeah do your best to put in recommended spec but honestly 89 is pretty close to 91 and Ive never had any issues doing it occasionally other than noticing a bit less power and mpg.
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