Premium fuel for the 2.2

[fffourtwenty]

Excellent luck so far bringing my 1990 Legacy 2.2 Estate back from the dead, many small fixes, AGIP ATF fixed the torque-binding straight away, trips to the local breaker yard fixed all the missing bits

 

I bought the car for $250 as-is where-was and it has turned out to be a very reliable car so far and thank goodness the previous owner eliminated the air suspension! Currently has 288k km

 

Noticed lately that when I feed this car Premium fuel, like Sunoco 100 or higher, it runs much quieter than if i use the standard 89 from Shell or the like, I know the boxer configuration makes for a bit more noise or maybe just a characteristic "sound" but it changes noticeably with the 100+ fuel

 

We're at 1300+ metres elevation here and it's been said that the higher-octane fuels are redundant at this elevation but wow does it make a difference

 

Anyone else have any fuel-use input? Additives?

 

D

[sqc151]

first of all. subaru never made an estate. its a gimmick the dealers use to sell cars.

 

secondly, i would run 87 oct in the car. thats what is it tuned for. maybe once a month run a higher octane, but all ur doing is wasting money. 93 and higher is for turbo cars and some of the newer luxury cars.

[Platinum_Racing]

Most of the time cars with higher compression ratios use high octane fuel because it is harder to ignite. Since the fuel is harder to ignite it is less prone to pre-ignition (AKA: Knocking) caused by hot spots in the combustion chamber. The higher the compression ratio of a vehicle, the hotter the combustion gasses become in the chamber as a result of the increased pressure. The hotter the combustion gasses get, the more likely the fuel is to ignite early.

 

If it runs that much better with high octane fuel chances are there is a lot of carbon buildup in the combustion chamber. Excessive carbon build-up can also lead to hot spots causing knock, but its fairly uncommon nowadays with all the detergents/additives in gasoline.

 

I hate to say this, but you should try and figure out if the increase in performance is the placebo effect, or if the car really takes a liking to high test fuel.

[ehsnils]

There is another factor too - and that is if the ignition advance is incorrect. Especially if there is a bad knock sensor.

 

Just do a general checkup of the engine to see that it conforms to specs. Include compression test.

 

If everything checks out try to find some suitable additive to the fuel that's intended to clean out soot. And a few hours of long hard driving where the engine has to work harder can burn off excess soot too. Just keep an eye on oil level and water temp when doing it. It's way cheaper than to tear down the engine for a pure cleaning.

[wish]

running 93 isn't a waste of money on an NA car. i run 87 in my legacy, but in my NA impreza i got better gas mileage running 93 and it was only a few more dollars per tank so it evened out.

[Platinum_Racing]

All I'm going to say is that the only reason octane is used in gasoline at all is to prevent knocking. The higher the octane, the harder the gasoline is to ignite. Its perfect for high compression or turbocharged engines where hot spots in the combustion chamber can cause potentially harmful pre-ignition of the fuel. Sometimes build up in the combustion chamber can cause a slight ping, which higher octane fuel can help get rid of, but its not made to give cars extra performance. Any benefits to using higher octane fuel is in direct relation to the cars running condition. Higher octane fuel doesn't necessarily have a higher potential energy, its just harder to ignite.

 

Car manufacturers have gotten exceedingly good at designing combustion chambers without hot spots, reducing the need for higher octane fuel. Gas stations try and make people think that higher octane fuel is better for your car by tricking them into thinking its either cleaning something, or making it run better. They've succeeded, and now the world is convinced that the key to maintaining a car is to put a full tank of "Supreme" or "Premium" fuel in there Toyota Camry once a month. All they're doing is coating the pockets of the oil companies.

 

If the oil companies called 93 octane.... 93 octane instead of "PREMIUM" or "SUPREME" or "V-POWER" 75% of the population would never buy it. Its advertising, and its good advertising. Why put plain old "REGULAR" in your car when "FOR $0.24 MORE PER GALLON YOU CAN HAVE SHELL V-POWER!!1!!!!1!!1!!111omgwtfbbq"

 

 

 

 

Its the same reason why the McDonalds golden arches look like a pair of tits and their color scheme is designed to make people more hungry. But it works.....