Gas in the WRX?

[Below Zero]

So the manual says premium....blah, blah, blah, but can you put in regular or plus and not harm the car?

[72Twenty]

Wouldn't is cause engine knock?

What about using regular and adding octane booster?

[snwbdrhoon]

i have a audi a4 avant.
i have been experimenting with the whole gas thing (regular, premium, super)...

the best bet is to add octane additive to keep things going smoothly. with regular the car ran fine, but the turbo was a bit delayed and not smooth. same thing to a lesser degree with the premium.

i did watch a guy in a BMW 5 series fill up his car with super and blow past the $50 mark.

[Obstruction]

Modern engines will usually limit engine performance (revs) in order to prevent knocking (pre-detonation) when fuel with a less than optimal octane level is used. So even though you may not hear the knock you may have an issue. It is likely that the car will not perform as well and possible that you may do some damage.

This is a good basic explanation of how octane from "How things Work"

__________
The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.

________

Octane boosters? No real experience. I'm a little skeptical. Usually the companies selling these kind of products aren't huge brands with a lot to lose if their product fucks up so ...

[snwbdrhoon]

good explanation.

small companies?

http://www.stp.com/fuel_oct_boost.html

some more info: i definitely see it as a short term solution. i will be varying between premium and super at the pump until things stablize.

http://www.cars.com/carsapp/national...odaysgas1.tmpl

[Shrubs]

Stick with what the manual says. 90 or 91 octane is probably the lowest you should run. Like holmes said above, it's all about knock. Your engine was designed to run at a high compression and all kinds of bad things happen when you start running lower octane fuel in it. You can get away with it in emergencies, but I wouldn't make a habit out of it, and especially keep your foot out of it if you do have lower octane fuel in there.

Octane boosters can work for you, but I would be very careful. A lot of times they are made with ingredients that eat up fuel lines and kill oxygen sensors, which get expensive real fast. Get on some WRX forums and find out what people are using effectivel before you go crazy with octane boosters. Also, get familiar with calculating octane for a tank of fuel. Octane boosters usually only bump up the octane by about .1-.2 octane points per bottle in a regular tank of fuel.

Usually, you are better off just buying 91-93octane at the pump after you do all the math. Don't get irritional just because gas is going up. People are losing their minds over this.

[Obstruction]

Corporate ownership -- You're right STP isn't a small comapny and they've mada lot of $$ in the additive bidness over the years.

If I'm not mistaken your Audi prolly calls for 91 octane and most of the premium in New England is 93. Mixing Regular (87) and premium (93) would probably do the trick. ... Forget it I just read your link which details this trick.

One warning careful not to overuse the additives. I blew the engine up in a chevy many years ago when I was young and foolish (I'm not young any more) by loading in too much alkyhol based additive.

[StroupSkier]

Turbocharged engines don't have a compression ratio as high as other performance engines. The problem occurs when the turbo kicks in. You could get away with a lower octane grade IF YOU CAN KEEP YOU FOOT OFF THE GAS!

However, if you use the low octane and drive like a maniac, you stand a good chance of throwing a rod.

The WRX does not have as low a compression ration as most turbocharged cars though - 8.2:1. This is more on line with a Mustang Cobra and a little lower than the Audi A4s. My old Probe had a ratio of about 5:1.

I would stick to the high octane myself.

BTW, just drove back from lunch, and there was a line 50 cars deep with police officers routing trafic around the station. Come to find out that there is a rumor going around that we will run out of gas in Raleigh, NC sometime around 4pm. The governer is saying thsi is not the case though.

[Below Zero]

Thanks for the info. The car is too valuable to take any chances, plus you can not drive that car slow, it's impossible. I'll sack up the cash and stick with the premium.

[Hugh Jass]

...You could get away with a lower octane grade IF YOU CAN KEEP YOU FOOT OFF THE GAS!....

Literally. The only time the turbo isn't spun up with that car is at low enough engine speed so that it hasn't gotten spinning yet.

Mine is still getting the high test. An extra $1.20 a fill up over mid grade doesn't seem like a problem.

[bad_roo]

The car's knock sensor should theoretically do the job for you.

[funkendrenchman]

As Hugh said the price difference isn't much. It stays the same even if the overall price is going up. You're spending $2.80 more per fill up no matter what the cost is. If it were 90 cents/gallon it would still be $2.80 more per fill up. One fill up a week X 52 weeks equal about 150 bucks/year which in the grand scheme is almost nothing. (assuming 14 gallons/ tank which is the most I put in at a time)

[Core Shot]

The car's knock sensor should theoretically do the job for you.

What the fuck do you know about cars? phhhht.

I vote for mid-grade as a good compromise. You feel good about saving money and feel good about almost using the right octane.
I've done it for years and haven't blown up any engines yet.

[bossass]

Premium is a sham. Don't buy the lie.

[nealric]

Premium is a sham. Don't buy the lie.

If you are running a low compression normally aspirated engine, yes.

With a turbo/high compression, running low grade really will cause problems.

[verrückter]

$50- if only I were so lucky...a tank of diesel cost me EUR 75.00 the other day near Bielefeld.

[phUnk]

In before some dirty hippy chimes in with "ride a bike!"

[StroupSkier]

Literally. The only time the turbo isn't spun up with that car is at low enough engine speed so that it hasn't gotten spinning yet.

Mine is still getting the high test. An extra $1.20 a fill up over mid grade doesn't seem like a problem.

The 1000 mile breakin period was probably the longest time in my life...

[Dexter Rutecki]

The car's knock sensor should theoretically do the job for you.

True in terms of preventing detectable knock, but not for protecting the engine in the long term. I remembered reading about this awhile back, and actually found it again. I know roo probably doesn't know who the car talk guys are, but they know everything about cars, went to MIT, and are basically wicked smaht.

Ray: Most modern cars have knock sensors, which detect pinging, which is often caused by the wrong grade of gas. When the engine pings, the computer retards the spark timing to compensate for the lower octane. That's designed to prevent engine damage if you get a bad tank of gas or travel someplace where the correct octane is unavailable.

Tom: But it's not a good idea to run your car with retarded timing over the long run. Among other things, you'll force the engine to run hotter than it's supposed to run, which will shorten its life. And you'll force it to run rich, which can eventually ruin your catalytic converter.

Ray: So I'd say you're stuck with premium unleaded, Conrad, at whatever octane the owners manual recommends. It's a good reminder to the rest of our readers. Before you buy a car, find out what kind of fuel it requires. If you don't, you may be unhappy to discover that you're going to be out an extra 25 cents a gallon at every fill-up for the foreseeable future. © 1999 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

[Markhpnc]

Hey Below Zero (or anyone else), how does the WRX perform in snow? Right now I drive a Civic DX hatch (most likely under 100hp ) which is good on gas, but I can not get up a snow covered mountain road to save my life. I have always wanted to get a Civic Si, but recently I was thinking I should maybe be looking at AWD for snow purposes. I live in NC so I don't drive in the snow too often, but it does happen sometimes without notice when I go to mountains to ride and it limits my options of places I can go. Plus I may be moving out west or up north sometime, so it could be more of in issue. I don't want an SUV or wagon, so the WRX or STI seems like it has everything (AWD, crazy power, etc.) What kind of tires do you use on it?

[funkendrenchman]

Hey Below Zero (or anyone else), how does the WRX perform in snow? Right now I drive a Civic DX hatch (most likely under 100hp ) which is good on gas, but I can not get up a snow covered mountain road to save my life. I have always wanted to get a Civic Si, but recently I was thinking I should maybe be looking at AWD for snow purposes. I live in NC so I don't drive in the snow too often, but it does happen sometimes without notice when I go to mountains to ride and it limits my options of places I can go. Plus I may be moving out west or up north sometime, so it could be more of in issue. I don't want an SUV or wagon, so the WRX or STI seems like it has everything (AWD, crazy power, etc.) What kind of tires do you use on it?

Great, except in really deep snow where clearance becomes an issue. I use Continental Xtreme Contacts... get rid of the Potenzas first thing.

[Markhpnc]

Yeah I thought about that too because if snow wasn't an issue I would probably lower it an inch or so. I guess ground clearance is something you sacrifice without an SUV. Is that an all-season tire? It would be nice to not have to change them.

[Core Shot]

http://www.usatoday.com/money/autos/...emiumgas_x.htm

"I personally use regular even though my owner's manual says you'll get better performance with premium," says Lewis Gibbs, consulting engineer and 45-year veteran at Chevron oil company. He's chairman of Technical Committee 7 on Fuels, part of the Society of Automotive Engineers (SAE) Fuels & Lubricants Council. Gibbs knows gas.

"My wife runs midgrade (89 octane) in her car, and it's a turbocharged engine" meant for 91-octane premium, he says.

Premium — gasoline having an octane rating 91 or higher — is just 12.1% of sales this year, down from 13.5% in 2002, when it was 22 cents a gallon cheaper, and well below the modern high of 20.3% in 1994, when it was 49 cents cheaper, according to industry and government data. Despite the allure of premium, once they abandon it, most motorists don't come back, the data suggest.

For every dime increase in the price, sales of premium gas drop 1%, Bob Johnson, general manager of gasoline and environmental services for the 7-Eleven chain, figures, based on data back to 1998.

The main advantage of premium-grade gas is that it allows automakers to advertise a few more horsepower by designing and tuning engines to take advantage of premium's anti-knock properties. But auto engineers generally agree that if you use regular in a premium engine, the power loss is so slight, most drivers can't tell.

"I go back and forth, and I'm hard-pressed to notice" whether there's regular or premium in the tank, says Jeff Jetter, principal chemist at Honda Research and Development Americas. He drives an Acura designed for premium.

Import brands, especially, use premium fuel to distinguish their upmarket models. Most Toyotas, for instance, are designed to run on regular or midgrade, while the automaker's Lexus luxury brand prefers premium. Same with Honda and its Acura luxury line.

"Generally, the more expensive the vehicle, the higher the expectation for performance and the more the customer is willing to pay for fuel," says Pete Haidos, head of product planning for Nissan in the USA.

Actually, the price debate is nearly worthless. At 20 cents more for premium, pumping 20 gallons of it instead of regular would cost $4 more. Annually, that's a difference of $171 for a vehicle that averages 14 miles per gallon — as some big sport-utility vehicles do — and is driven 12,000 miles a year.

Gasoline retailers and refiners like high-test because it's more profitable than regular-grade gas is. The retailer paid about 8 cents more for the premium you pay 20 cents more for — though that margin can swing wildly. Refiners make a few cents a gallon more on premium than on regular when they sell to wholesale distributors.

As long as it's clean

Profit is meaningless to the modern engine, which, regardless of what's specified in the owner's manual, hardly cares what you use — as long as it's clean.

Today's engines use highly evolved versions of a device called a knock sensor to adjust settings automatically for low-octane gas. And more engine control computers have adequate memory to allow separate sets of instructions for various octanes. The engine control computers keep pushing to maximize performance on whatever grade of fuel is used.

Extreme pressure inside the cylinders causes knock, which is the sound of the pistons literally rattling inside the cylinders. Too much too long can damage the engine. A little now and then won't.

The only modern engines that should really need premium are those with superchargers, which force-feed fuel into the cylinders. "You're driving along and just tramp the gas and the knock sensor cannot sense the knock fast enough in some cases," because the supercharger boosts pressure so fast, says Bob Furey, chemist and fuels specialist at General Motors.

Burning regular when the owner's manual specifies premium won't void the warranty, nor damage the engine, even the most finicky automakers say. "You're giving up perhaps just a little bit of performance that a customer wouldn't really even notice, it's so slight," says Furey.

Automakers say they don't test premium engines on regular to check the difference, but some auto engineers estimate that power declines roughly 5%.

"We can't guarantee the vehicle will perform as specified if other than premium fuel is used," says Mercedes-Benz spokeswoman Michelle Murad. All U.S. Mercedes engines specify premium.

[brit]

which is the sound of the pistons literally rattling inside the cylinders.

Thats's a pretty technical description - not to mention wrong. I think whilst that article had some good points, a lot was bull (like the above) and makes sweeping generalisations.

Hey, shock horror, some bits of my degree were a little bit useful!!

R

edit: typo

[Core Shot]

Duhhhh,
You may be a little stupid if you think I posted that for the journalists uneducated blatherings (which carry almost as much weight as the uneducated baltherings of most of the posts in this thread).

The highlighted sections are direct quotes from engineers and chemists who are a wee bit more knowledgeable than I am.

Personally, I am still looking for technical info and opinion in support of premium (other than Click and Clack, no offense). The techno quotes I posted were the best I could find.