According to the manual you must use Premium fuel. 91+ (for us 93). The extra cost at the pump for 93 will be offset by the increse in performance, engine life, and fuel mileage.

when i had my RSX, it could run off 87, it was designed for 87, but the enthusiast that i am, i want only the best, so i fed her 93 for 3years (in NY, NE prices are a joke compared to Westchester County) till she went off lease. w/ 93 i was able to get 33mpg, my friends w/ RSX's on 87 were getting lower #s and had to fill up more often.

It says 91, no less. dont risk it.

 

Premium. Its recomended. SOA prolly will void your warranty for not using it, they do for everything else.
uncle lewie

 

Use premium,your car will love you for it.

 

According to the manual you must use Premium fuel. 91+ (for us 93). The extra cost at the pump for 93 will be offset by the increse in performance, engine life, and fuel mileage.

when i had my RSX, it could run off 87, it was designed for 87, but the enthusiast that i am, i want only the best, so i fed her 93 for 3years (in NY, NE prices are a joke compared to Westchester County) till she went off lease. w/ 93 i was able to get 33mpg, my friends w/ RSX's on 87 were getting lower #s and had to fill up more often.

It says 91, no less. dont risk it.

thanks guys for the quick and meaningful responses

good point. don't wanna risk messing anything up. plus its only 150 dollars more per year
i did the nerd-math and tha'ts what it came out to

i guess its definitely worth it to save the car, for just 150 bucks a year, plus i'll have better performance =)

 

Use premium,your car will love you for it.

Must agree!

 

if you can't afford to use the proper fuel why would you buy a WRX?

 

I'd use premium. I had a 2nd gen elclipse trubo that was supposed to run off premium and of course being in college I took the cheap way out and used regular for 4-5 years. By the time the car had 75k miles on it the engine ran like crap. I had so much carbon buildup and it never really ran well after 90k miles despite taking care of it (ither than ignoring premium gas).

 

According to the manual you must use Premium fuel. 91+ (for us 93). The extra cost at the pump for 93 will be offset by the increse in performance, engine life, and fuel mileage.

when i had my RSX, it could run off 87, it was designed for 87, but the enthusiast that i am, i want only the best, so i fed her 93 for 3years (in NY, NE prices are a joke compared to Westchester County) till she went off lease. w/ 93 i was able to get 33mpg, my friends w/ RSX's on 87 were getting lower #s and had to fill up more often.

It says 91, no less. dont risk it.

There's no reason to run anything higher than 87 octane in a car that was designed for 87 octane. You are just throwing money away by putting higher octane gas. Octane is a knock or pinging preventor. The higher octane is for higher compression engines to prevent pinging or detonation (fuel/air igniting before the spark plug fires) in the cylinders.

You said that your gas mile was higher than others with the same car running regular gas. There are too many variables in that "experiment" especially that different people were driving the different cars. Your driving habits were probably a lot better than theirs. Even if you have the same driving style, maybe they let their cars ideal in the driveway on cold mornings longer than you did.

Getting back to the original poster's question, don't run anything more or less than the recommended octane rating in the owner's manual. If you have a modded engine with increased compression or boost, that's a different story. Higher octane will be needed, but you definitely never want to run less than 93 octane in your WRX.

If you travel to higher altitudes, such as in Colorado, you'll notice that the highest octane gasoline they sell there is 89 or 91 and the regular stuff is down around 85 octane. That's because the air at high altitude has less oxygen and the engine doesn't need as much octane to prevent knocking or pinging.

Here are some good reads:
http://www.chevron.com/prodserv/fuels/gas_qanda/api_octane.shtml
http://www.cyber-north.com/autotipnet/octane.html
http://www.petro-canada.ca/eng/prodserv/fuels/6823.htm

In my old Jeep, the engine would knock a lot at high RPMs and with high-load driving, like on the highway. If I knew I was going to be doing highway driving on a particular tank, I would fill up with 89 or 91 and the knocking was significantly reduced. The rest of the time I used 87. And it ran fine.

I hope this helps.

 

^ everything you need right there about gas hahaha

thanks, the links were helpful

 

stick with 91 or higher (read my quote)

 

Keep in mind that the increase will be less than 150 because you will get better milage.

 

What kind of gas a car takes is one of the factors that should be involved when considering an automotive purchase. Please use the 91 that it was engineered to use. :wiggles:

 

There's no reason to run anything higher than 87 octane in a car that was designed for 87 octane. You are just throwing money away by putting higher octane gas. Octane is a knock or pinging preventor. The higher octane is for higher compression engines to prevent pinging or detonation (fuel/air igniting before the spark plug fires) in the cylinders.

IMO octane differences aside, the detergents in the higher octane gas warrant the extra cost (in cars that don't "require" it). not to beat a dead horse now but in the wrx, use 91+ period. that's what it was designed for, and being a relatively highly boosted forced induction car, it needs it. if you don't, your mileage would decrease (slightly) because it'll pull timing and you'll consequently put your foot down harded, but also you run the risk of detonation, especially say in the hot summer. i just did the math and on a 16 gallon fill-up with a $.20 price difference you're spending $3.20 per fill-up extra. I fill my tank 4 times per month which makes a whopping 13 bucks . Seriously, if that's too much to pay than buy a different car.

 

Use the premium and give up something else for the time being, or try to earn a few extra bucks a week. If your engine is knocking, even a little, on lower grade fuel you will kill it. A couple bucks a tank will seem like nothing if you have to pay to replace the whole engine! Plus, you will get used to the cost after a few fills and it will seem like no big deal anymore to pay it.

 

damn, should have taken advantage of some of my basic math skills before asking this question... lol whopping 13 bucks

thanks guys for all the help. Looks like i should be worrying about the insurance instead

 

Darrel beat me to the punch on fuel.

The "Premium" label does not mean better fuel. In fact, a gallon of 93 has the same potential energy as a gallon of 87. You will not likely get better performance swapping fuels in a car not made for it.

The higher octane number just indicates a fuel's resistance to igniting. It's typically used for engines that run high temperatures and high compressions...two things that are present on a turbocharged car.

The quick and dirty:

Putting 93 in a car made for 87 = extra fuel in the cat, cat goes bad sooner

Putting 87 in a car made for 93 = knock damage to the engine and messed up computer and knock sensors

Spend the extra $5 a tank. It's worth the lack of hassle.

 

Technically if the engine management computer is good it will be able to advance timing when you use higher octane fuel and this will give you a bump in power. It's not huge but it does happen.

 

If you want to get the full potential of the car, use 93. The ECU will have to pull timing if you use lower octane and the car will feel sluggish.

 

if you can't afford to use the proper fuel why would you buy a WRX?

 

u should read more carefully.
when u open the gas cap,
it says "Premium Unleaded Only"
=)

 

i just bought my 05 wrx monday. The dealer told me this about using premium and such.
He said that if i used 89 octane i should use 89 octane for every fill up. Switching back and forth between 93 and 89 will cause the computer trouble. He recommended 93 octane for better performance though. But if i wanted to i could use 89 and have no problems.

 

i just bought my 05 wrx monday. The dealer told me this about using premium and such.
He said that if i used 89 octane i should use 89 octane for every fill up. Switching back and forth between 93 and 89 will cause the computer trouble. He recommended 93 octane for better performance though. But if i wanted to i could use 89 and have no problems.

There's also a little thing you probably signed that says that the dealer isn't responsible for pretty much anything warranty-wise, so if you go against the owner's manual and use 89 instead of 91 (or better) octane and end up needing warranty work as a result, guess who's not going to pay for it...

 

If you want to get the full potential of the car, use 93. The ECU will have to pull timing if you use lower octane and the car will feel sluggish.

Around here, I have to fill up with 93 all the time anyhow. It's hard to find a station that sells more than the three standard grades of fuel; 87, 89, and 93. Once in a while I see 91, but that's probably once a month when I don't need to fill up.

 

There's also a little thing you probably signed that says that the dealer isn't responsible for pretty much anything warranty-wise, so if you go against the owner's manual and use 89 instead of 91 (or better) octane and end up needing warranty work as a result, guess who's not going to pay for it...

Then you need a new dealer. Even if I signed something like that, the dealer told me this. Im sure he wouldnt say something to me that would void the warranty of my car, even if i did have problems i think he would fix them. And if he wouldnt do warranty work then someone would be getting a lawsuit :baaa:

 

I was thinking of trying reg gas when it was cold out, below 30 deg. But for the small price difference not worth the worries. Besides I paid over 24K for this new car. To spend a couple extra bucks per fill up to "Care" for it is nothing.