Subaru Crosstrek and XV Forums banner

1 - 20 of 55 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
Hi Guys, i have a question, i used sometimes Gasoline super 91 (5 times) (i confessed),
my question is: with this (91 octane) a i did worse thing to my engine?
 

·
Registered
2017 Crosstrek Limited
Joined
·
1,481 Posts
Just to your wallet :)
 

·
Registered
2021 Crosstrek Limted
Joined
·
54 Posts
I have used, still use 89 octane in all my vehicles fro the last 30 years..... least one lasted 20 years 230K retired due to an intermittent overheating issue and needed reliability.
 

·
Registered
2021 Sport 2.5 cvt
Joined
·
74 Posts
It can't and won't hurt your engine, but you also won't get anything out of it.
Any unburnt fuel going into the exhaust is not going to do anything Good. I also would not want any associated miss fires resulting from the high octane fuel not igniting where/when it should.
Certain engines, high compression, require the high octane. Using 87 in them would be equally a bad idea.
 

·
Registered
2021 Crosstrek Limted
Joined
·
54 Posts
Michael all cars you had are Subaru's?
Nope:MGA and Healey 3000 [Ran "Ethyl"(Premium) as they called it back in the day on those two],.... FJ40, BMW320, Volvo, Jeep, Subaru.... Subaru is the latest but all the others lasted well over 150k and still running fine when sold.

No Knocks, No Pings, No Errors...... Ever.... just luck I guess.
 

·
Registered
2019 Limited with Eyesight
Joined
·
407 Posts
I agree. Using anything above 87 is a waste of money. No better performance, no increased mileage, just a waste of your hard earned money.
 

·
Needs a Butch car
2020 Crosstrek Premium
Joined
·
914 Posts
Any unburnt fuel going into the exhaust is not going to do anything Good. I also would not want any associated miss fires resulting from the high octane fuel not igniting where/when it should.
Certain engines, high compression, require the high octane. Using 87 in them would be equally a bad idea.
Huh? Octane doesn't have anything to do with the fuel air mixture, it's a rating of the fuels resistance to pre ignition. It's not like 91 is high enough octane to not ignite from the spark, and once some of it ignites, it all will. That's literally how engines work. The spark plugs starts the ignition, not compression.
If you run very high octane gas in your car - say 100 octane unleaded - that just makes it extra likely that it'll ignite from the spark and not from something else.
That's completely unneeded of your car is designed for 87, but it couldn't hurt.
 

·
Registered
2021 Crosstrek Base Crystal White Pearl
Joined
·
16 Posts
The choices I have here in southwestern NM are 86, 88 and 91. When I took delivery of my car the dealer filled it with premium per the advice of a tech. 🤷🏻‍♂️

I use the 88 octane. 🚀
 

·
Registered
Joined
·
29 Posts
And also keep in mind that a modern engine has so much computer control that even a lower grade fuel won't do harm since the spark advance and fuel/air ratio is changed by the computer for the conditions. "Back in the day" things were very different and the octane actually did make a difference in engine wear. Today, not so much. Perhaps in a Ferrari but not in a Subaru.
 

·
Registered
Crosstrek Limited 2021
Joined
·
121 Posts
Subaru runs much better on 89 octane and the proof is the better efficiency by ~ 10%. Anything above it - is a complete waste. It can not take advantage of higher octane gas (>89) due to design. With 87 you will get momentary knocks on heavy loads - it means ECU will retard ignition timing to counter it and your efficiency will drop. No any knocks on 89, so efficiency is at the top, so is power. Money wise it is a wash (price difference vs. better efficiency and power), but you get better performance with 89 as well.
 
1 - 20 of 55 Posts
Top