Octane needed for 05 Legacy GT

[gjeff80]

Hi All,

 

I just picked up my first Legacy. I got an 05 Legacy GT. Now my buddy that is big into Subaru's tells me that i MUST run high octane fuel in this to get better gas mileage? Is that the case? What happens if I run regular 87 octane fule in this thing? Around here right now, 87 octane is 2.45 per gallon and 93 is 3.15 per gallon.

 

 

Could someone let me know if higher octane fuel will still be necessary?

 

Thanks

Glenn

[technicalgarage]

You should run 91 or higher to reduce the chance of detonation (knock). Anything lower has a chance of knock on the turbo model. I'm sure 87 will work with the ECU pulling timing to prevent knock, but I definitely wouldn't recommend it.

 

Is saving a few dollars each year really worth risking your engine's internals? I certainly don't think so.

[Pataker]

I am pretty sure the owners manual recomends 91 or better.... check the owners manual for a sure fire answer though

[Aczwild]

Short story: 91+ is necessary for your vehicle as indicated in your manual and on the door for the gas cap, dont deviate

[Pataker]

thats what i thought...

[gjeff80]

So, is there any benefit in running 91 vs 93 octane? I will try and run atleast 91 octane. I will drive it slow for now to burn out this tank of 87 octane and then add some better stuff in.

 

Will I get better MPG using higher octane fuel?

[one69chev]

if you can't find 93, use 91. you cannot drive an LGT and put regular in it. if that is what you plan to do, its best to get a non-turbo which will perform fine on regular. and no, you will get no mpg gain from premium, but is a requirement for the LGT's

 

and be prepared for the inevitable flames. it seems like a couple times a month, somebody starts a thread on this topic. use the forum search option, check your owners' manual and i believe the premium requirement is indicated in the fuel door.

 

good luck and welcome to the leggie boards

[gjeff80]

What are the inevitable flames?

[johnAWD]

"Flaming" posts from fellow LGT members. This issue has been discussed in depth. If the car didn't require 91 octane, it would not be in the manual nor under the gas filler door. Educate yourself on what octane numbers mean and you'll be happy that you did.

[NJLGT]

yepp, better put you flame suit on . seriously though run the highest grade gas available... i only use shell vpower 93 octane but sunoco also has very good gas. i wouldn't put anything else in my car except for 93 octane from either gas station.

[c-lo]

may I be one of the first:

 

we've all been guilty of it at some point, but did you not know what you were getting and what type of fuel it needed?

 

and did you put 87 octane in before or after your friend told you not to?

[drewmanman3]

im pretty sure i read somewhere that if you dont put the required gas in your car youll hurt your mpg. i could be wrong. i know when i had my rubicon it said only but 87 in it because it will worsen gas mileage

[subarovsky]

Just put Premium in it and it will run fine, If your real worried about gas mileage you should have went with a Prius, for the power these cars make and the AWD they are very good on gas in my opinion, and if you sit down and figure it out using Premium VS. Regular only costs you about $240 more per year. good luck

[RabidWombat]

im pretty sure i read somewhere that if you dont put the required gas in your car youll hurt your mpg. i could be wrong. i know when i had my rubicon it said only but 87 in it because it will worsen gas mileage

 

This depends a lot on the car and how aggressive the tuning profile is. For example, newer Audi's will run fine on 87, but you'll lose power compared to using 91. Subaru runs a more aggressive factory tune and higher boost pressures. If you run 87 for any significant period of time you will significantly shorten the engine lifespan.

 

When I purchased my LGT the dealer warned me to only use premium. They said that they a customer had brought in an FXT that needed a new engine after 50k due to always running on 87.

[one69chev]

regular in a turbo subie will not only "worsen" your mpg, but it will most certainly "worsen" your engine. i would return the veh under a temporary insanity claim, and then get a naturally aspirated subie. you'll get decent mpg and awd in a very attractive package, and no fuel concerns.....

[timmahh]

More or less - higher octane = higher combustion temperature

 

If you put 87 in, you run the risk of the fuel/air mixture detonating before the spark plug fires... which is bad. 91 octane burns at a higher temperature than 87, so it's able to deal with more compression and heat before it ignites.

 

 

(I think.)

[one69chev]

http://i47.photobucket.com/albums/f159/RaulMonkey/Animated/beating-a-dead-horse.gif

[Mickeytl]

If the car has over 120k miles, then you can put any kind of gas you like...

[Impulse]

If the car has over 120k miles, then you can put any kind of gas you like...

wut? 404 funny not found. if you dont like your engine, listen to this guy.

 

otherwise, dont. last time you opened your gas cover you should have noticed the "PREMIUM ONLY" so, fill up whatever PREMIUM is around you, 91+

[Yamarocket630]

Just for fun I'll throw a wrench into the works... In cold temps you can run 87 Octane all you like. Your engine is much less likely to detonate running on cold air, and winter blend fuels have more ethanol, which while it may still be RATED at 87 octane, will have the effect of reducing detonation further due to ethanol's latent heat absorbency.

 

I wouldn't recommend this for a tuned or modded car though.

 

I dare you to challenge me with FACTS or science, not "my cousin works at the delaer and saw a engine explode one time because the owner used mobil1 and 87 octane at the same time!!!one1"

[one69chev]

this debate/thread/inane line of conversation has been exhausted to death and back on these boards. it's really quite simple, if you buy a turbo, be prepared to use effin premium, if you buy a naturally aspirated subie, use what ever fuel you want.

 

the point is, don't buy a veh that requires the good stuff and then cheap the f*&k out just to save a few pennies per gallon. the other 9000 threads on the boards concerning the exact same effin' topic all the same effin' thing; and that's the frustrating part. do a search, find some info, get some answers. that's what the search function if for dammit.........................................................................................................