anyone try 87 octane in their gt?

[941LE]

It takes more heat to combust higher octane fuels, thus higher octane inhibits pre-detonation (knock) as cylinder pressures/timing increase. In theory a car would make = or greater power on lower octane assuming = timing without knock not being an issue. Higher octane means you can run more boost, more timing and thus make more power. LGT being a boosted application, higher octane should be used as a precaution if nothing else. Effective compression is increased while boosting and fuel and weather will vary as will every car. Being intercooled helps immensely as does having low compression, both are almost nesessary on a factory forced induction car. Subaru recommends premium for a good reason, gotta pay to play.

[johnAWD]

Right on, 94.

 

VVG - your avatar owns me.

[altanic]

well, glad I read this. I won't feel so bad buying premium anymore just 'cuz the manual says so.

[Jon in CT]

It is better to keep your mouth shut and appear stupid than to open it and remove all doubt. - attributed to Mark Twain.

 

Let's see who should've kept their yap shut.

 

View octane as a burn inhibitor. More octane gives your fuel a higher flashpoint, which defends against detonation/preignition/knock.

The flash point is the lowest temperature of a sample at which application of an ignition source causes the vapor of the sample to ignite. For gasoline it is so low (normally below -40°C/F) that it cannot be determined by any standard methods. Diesel fuel in the US has a minimum flash point of 38°C (100°F), much higher than gasoline, yet its octane rating is in the crapper.

 

It takes more heat to combust higher octane fuels, thus higher octane inhibits pre-detonation (knock) as cylinder pressures/timing increase. In theory a car would make = or greater power on lower octane assuming = timing without knock not being an issue.

All it takes to combust higher octane fuels is a spark. Adding tetraethyl lead to gasoline doesn't decrease its power but does amazing stuff to its octane rating. The octane rating of methanol is much higher than gasoline yet its specific energy is also higher than gasoline. A fuel's octane rating has no correlation to the power it produces.

[brooklyngenius]

you'll void your warranty if they catch you with lower octane. Turbo cars REQUIRE high octane.

[Garandman]

///

 

VVG - your avatar owns me.

Do a google search for Nikki Cox. She seems to have lost some weight for this season of Las Vegas, so her boobs are only very large instead of breathtaking.

[-Smoke_]

Nothin' but the best for my car...93 + Royal Purple oil!

[Aczwild]

you'll void your warranty if they catch you with lower octane. Turbo cars REQUIRE high octane.

This is very true also they will void your warranty

[chuckzul]

Been running regular 87 almost since day one. 11300 miles later, no problems detected.

[johnAWD]

It's nice that you guys are able to run 87 and not see any difference between it and 91/93. I wouldn't do it to my car, as there's a reason that the manufacturers 'require' premium in factory turbo cars. For the extra $3-$4 per tankful, I'll error on the 'safe side'.

 

I'd be interested in seeing a datalog of a run thru the gears from 0-120 on 87 octane, an ECU reset, and then another 0-120 run with 91/93. Maybe I just need to put down the crack pipe..

[gt_ltd]

Been running regular 87 almost since day one. 11300 miles later, no problems detected.

 

weak sauce. i have been running regular 85.

[JBLU24]

i only put 93 in my LGT and even then I'm particular- i only put shell or sunoco. BP/amoco if i must.

call me weird...call me dumb....i just know it works for me

 

now as for the over 100 taxicabs i operate- i have convinced a handful of drivers to put 93 for 2 tanks when all they put is water/urine with an 87 octane rating and they have been amazed. if these guys can be converted i'm sure anyone can.

for 3-5 bucks a tankful i just dont see why you would downgrade?

[hal9e3]

Using a lower than recommended octane fuel will NOT unconditionally void your warranty. Here's a direct quote from the 2005 Legacy Owner's Manual, page 7-2:

 

The 2.5 liter turbo engine is designed to operate using premium unleaded gasoline with an octane rating of 91 AKI or higher. If premium unleaded gasoline is not available, regular unleaded gasoline with an octane rating of 87 AKI or higher may be temporarily used.

For optimum engine performance and driveability, it is required (for 2.5 liter turbo models) that you use premium grade unleaded gasoline.

 

However, on page 7-3 the manual contains the following CYA blurb:

 

If it is determined that the (CHECK ENGINE) condition is caused by the type of fuel used, repairs MAY not be covered by your warranty.

 

So, as always Subaru (and all other auto manufacturers) reserves the right to jerk you around over warranty coverage. However, using 87 octane in and of itself is not an ironclad reason for denial of coverage. I do have to wonder tho, why'd ya'll buy the hot rod motor if you don't want to put hot rod fuel in it? A few other points. Vehicles are designed to produce the maximum performance/efficency using the recommended octane gas. Running them on a DIFFERENT octane, higher or lower, reduces power and mileage. C&D did a test a few years ago that proved this. Also, care in selecting the gas brand may produce better results as well. Octane ratings are the average of two different tests, one more strenuous than the other. So, two gasolines with the same R+M/2 rating may perform differently because one produced a higher octane rating on the tougher test. Finally, several manufacturers banded together to create a more rigorous standard for detergent gasoline to help prevent or reduce engine deposits. If you want to know more check out http://www.toptiergas.com