legacycentral bbs

ha ha i was sitting at the bank waiting in line and i saw the annual government fuel economy review for all the 08 cars.
it just gives the ratings and such of all the new cars imported to dealerships in the US.

http://www.fueleconomy.gov/ is the site if you are interested.


this is an actual quote i read in the magazine/terribly written collection of paper.

Premium Vs. Regular grade gasoline

"The reccommended gasoline for most cars is regular unleaded. Use of a higher octane gasoline than recommended by the owners manual does not improve performance or fuel efficiency; it only costs more money. Check your owners manual to determine the lowest grade of fuel you can use"


ok i know this really is true for SOME cars, but i just thought that it was funny that this info would be in the bank and that this information is being used to influence the average person looking to get a new car.


obviously this statement isn'y entirely true.

What is the false part?

I think he means to say that the 'false' part is where they tell you that its not a requirement to use Premium fuel in cars where the manufacturer has provided literature citing this.

But I think we all know the real truth. . .

vrg3 wrote:What is the false part?

Use of a higher octane gasoline than recommended by the owners manual does not improve performance or fuel efficiency; it only costs more money.


and tris91ricer;
thats the other point


i literally posted this thread like 30 seconds ago, you guys are too fast!

SubaruNation wrote:Use of a higher octane gasoline than recommended by the owners manual does not improve performance or fuel efficiency; it only costs more money.

You're saying our cars are a counterexample?

I thought our owner manuals recommended "at least 91 octane," rather than recommending an actual octane number... I think that's consistent with the statement above, no?

i literally posted this thread like 30 seconds ago, you guys are too fast!

We have no lives.

yes and no sir, and almost any car is an example.
although you CAN put less than 91 octane in our cars/other cars you will NOT get as good of gas mileage.
and have you also will not perform as well if you put less than 91 octane in it, i have tried it and its worthless when you put 87 or 89 in it. accelleration sucks ass and you will not go as far because the amount of energy contained in the fuel is less than that of 91 octane.

clearly this depends on alot of things, i just showed my friend this and he said if he puts 91 octane in his izuzu, it lurches and wont run very well.

i was just showing the fallicies of the government

vrg3 wrote:We have no lives

ha h ai know i have a geology final and a microeconomics final in less then 18 hours [/quote]

Don't over analyze blanket statements.

Some manufacuters use knock and timing stratagies that are more agressive than others. What this means is that, in some cases, you will make more power and get better milage by using 91+ octane gas. Even in vehicles marked for 87.

I have personally seen this in my old MX-3 GS. The computer basically keeps slowly advancing the timing until knock is detected. This means that after consistantly (weeks) using higher octane fuel the actual timing sits higher then would normally be supported with 87 gas. This behavior was observed with both the original 1.8 v6 and the swapped 2.5 v6, with thier respective ECUs.

10 years ago, when I was active in the Mazda community, this was common knowledge and well documented in Mazda circles.

I cannot comment on Ford, Mitsu, Subaru, Hyundia, Fiat or even new Mazdas, but for Mazdas in the early 90s, raising octane usually eventually lead to more power and better milage.

SubaruNation wrote:....because the amount of energy contained in the fuel is less than that of 91 octane.

I've always read the opposite, but honestly I'm not sure. It's not really an energy thing, it's resistance to spontainious ignition. When heat and pressure reach a certain point, the fuel starts to burn. If this happens to early, we call it knock or detonation.

There's more potential energy in the lower octane. It ignites more easily, which is a problem in some cases. My Mazda3 seems to like higher octane a little better, but I run 87 as it's fine with it.

The N/A Subaru didn't care what I put in except for the 85 I bought when I was driving through the desert back in 2000. I remember seeing the gas prices and thinking $1.56 for 87! F that, I'll just throw some 85 in it and save a few cents. There was just no way I was paying that much for gas.

SubaruNation wrote:although you CAN put less than 91 octane in our cars/other cars you will NOT get as good of gas mileage.
and have you also will not perform as well if you put less than 91 octane in it, i have tried it and its worthless when you put 87 or 89 in it. accelleration sucks ass and you will not go as far because the amount of energy contained in the fuel is less than that of 91 octane.

But the manufacturer doesn't recommend 87 or 89 octane except in emergencies!

And, like Steve says, 87 octane fuel usually contains more energy than 91 octane fuel.

i was just showing the fallicies of the government

And I'm still struggling to see the fallacy.

The factory recommendations are correct, and reliablle over any imaginable operating condition. Using higher octane fuel is not necessary and a useless expense, as it costs more to produce.

However, if the engine is built for higher output, the designers will require a higher octane fuel.

My wagon is tuned for 94 octane gas and the Alfa for 91.

vrg3 wrote:
But the manufacturer doesn't recommend 87 or 89 octane except in emergencies!

And, like Steve says, 87 octane fuel usually contains more energy than 91 octane fuel.

i was just showing the fallicies of the government

And I'm still struggling to see the fallacy.

obviously, the engine CAN and WILL run on a grade lower than the reccommended, and if it'a an emergency you CAN steal gas!
i was pointing out that 91 is necessary in our turbo subies...
and when the article stated that "higher octane fuel does nothing" that is complete Bullshit, and my othre point is that i read this from a government sponsored/subsidiezed whatever organization.
the information should be true and factual, not complete bs.
ok??

evolutionmovement wrote:There's more potential energy in the lower octane. It ignites more easily, which is a problem in some cases. My Mazda3 seems to like higher octane a little better, but I run 87 as it's fine with it.

The N/A Subaru didn't care what I put in except for the 85 I bought when I was driving through the desert back in 2000. I remember seeing the gas prices and thinking $1.56 for 87! F that, I'll just throw some 85 in it and save a few cents. There was just no way I was paying that much for gas.

yeah when i started paying for gas it was a $1.77 at costco and i was driving a ford taurus wagon (wtf was i thiking?)
it's ok though because i totaled it 6 months later ha ha!...along with 2 other cars
now the price in montizzle with STUPID EFFIN-OL is $3.35/gal.

I'm sorry,

I'm with Vikash here....I see absolutely nothing wrong with what you quoted.

I will requote, and bold the words that make that statement acceptable.

"The reccommended gasoline for most cars is regular unleaded. Use of a higher octane gasoline than recommended by the owners manual does not improve performance or fuel efficiency; it only costs more money. Check your owners manual to determine the lowest grade of fuel you can use"

Like I said, I don't see what's wrong with the above statement.

BTW, this is more ashtray material then Misc material....so I'm going to move it.

Yes, I agree with Josh and Vikash...if your vehicle needs premium fuel...the owner's manual will inform the owner of that; or it will be written on the fuel door or whatever (like the Legacy Turbo)

What has happened over the years is that people have thought that since because sports cars require higher octane fuel, that the fuel must therefore be causing the engine to make more power and that it will somehow benefit their normal cars, whether it be from a performance standpoint or that they believe it's better for the car.

As Steve, Vikash, Josh, and the article have said, the lower the octane is,the less energy is required for it to ignite. Period. 87 octane is easier to ignite than 91. Period. So why do high-performance cars want fuel that's harder to burn?

Well, gasoline ignites. We know that. And I'm making a blanket statement here that is probably not entirely true, but the result and byproduct of gasoline burning is essentially the same regardless of octane. The problem is, lower octane fuel will ignite QUICKER than higher octane fuel, and because high-performance engines make more of the energy that requires fuel to burn (be it a forced intake charge from a turbocharger or supercharger, or nitrous oxide, or high compression), a lower octane fuel will ignite quicker in a high-performance engine than it will in a regular engine in a normal car.

The problem is that the fuel usually ignites TOO quickly. It should make sense then that one of the synonyms for engine knock is preignition. The fuel is igniting before it is supposed to, i.e. before the piston is at TDC (again, blanket statement, as the optimal timing of ignition is dependent upon many things, but this is the basic idea). If the fuel ignites before the piston is at TDC, the force behind the explosion will stress the piston and rod and bearings and all other associated bottom-end parts in ways they were not designed to be stressed, and if you're lucky, all you'll hear is a pinging or a knocking sound. If you're not so lucky, you'll throw a rod through the block.

Now, in a way, you're slightly right SubaruNation. A normal engine CAN in fact benefit slightly (at least in terms of performance) with higher octane. The ECU can advance ignition timing slightly because it doesn't have to contend as much with preignition with 91 gas as it does 87 gas.

Want proof that a mass-produced engine benefits from higher-octane? The old 3.0 Toyota engine (the sludge engine) used to be rated at 210hp before the new SAE standards came into effect. Afterwards, it was rated at 190hp. There was no BS in that 210hp rating; it was real. But what Toyota did was run the dyno engine for an extended amount of time on 91 octane gas, long enough to allow the ECU to remap its fuel and timing curves to take full advantage of the 91 gas. Then, when it was dynoed, they ran 91 gas, because the SAE didn't disallow it. The new SAE standards dictate that the engine must be dynoed on the lowest octane gas the manufacturer claims it can be run on. So Toyota was then forced to dyno that engine on 87 octane, and the power rating went down from 210 to 190.

But that's an extreme example if you ask me. I'm surprised that the ECU for that Toyota engine is eager enough to use 91 octane that effectively. However, I believe that Toyota claimed that for 91 octane is 'recommended' for that engine, but will run on 87. Another example is the last-generation Honda Odyssey, which had 210hp as long as you ran 91, but had 205hp if you ran 87.

Most cars' ECUs do not do that though. They might advance it a little for higher octane, but they still play it safe, because the engine was not intended for high performance. That is the more complicated way of saying what the article said.

In fact, some new GM models, including my grandfather's Cadillac and my great-uncle's Silverado REQUIRE 87. Yes, if you put higher than 87 octane in it, the ECU will get mad at you and will actually throw codes in rebuttal.

One more factor is the car's age. As engines get older, they build up carbon (Subarus are actually quite bad about this), and carbon deposits in the cylinder actually remain hotter than the rest of the combustion chamber after the explosion. So when the incoming A/F mixture hits those carbon hot spots, it preignites. I run 89 octane in my N/A Legacy, even though it calls for 87 octane. Even still, I get pinging every once in a while. I attribute that solely to the fact that it has 181k miles on it and the engine is bound to have some carbon buildup in it.

But the initial argument still holds true. Again, I posted a novel, but for all practical purposes, as far as Joe P. is concerned, the article is correct. Most engines intended for daily use in commuter cars gather little to no benefit from using 91 octane gas.

The best Subaru example of this is the 3.0L engine. If you ask any fuji engineer they will tell you this engine MUST have 91 octain to operate normally (the owners manual says this as well.) If you ask anyone in the SOA sales department they will tell you "regular is ok" because to many soccer moms bitched about having to spend SO MUCH MORE on premium. In an extreem case near Seattle one dealership had a customer who couldn't even get out of his steeply graded driveway in the morning when his Tribeca was cold because the ECU was pulling so much timing because he was running our better than most 87octain regular here in WA.

I will say though.....my gf has a 06 outback with the 3.0 L engine, and all she runs is 87 octane fuel. I drive that car, and it runs pretty damn well.

I have put premium in it before, but don't really see much difference. I'm sure if I ran several tanks I might see a difference, but I can honestly say that it drives fine, and has enough power when running on 87.

ok Dubba Tee EFF mate?

i understood the "unless your car says so" aspect of it, but that was not the point. or at least it wasn't to me, just to you people.
the point was {spoon ready for launch} that premium does improve performance and fuel efficiency in SOME CARS. i also gave my experience with this point as an example, and since i only have one car, i can only show my experiences.

555BCTurbo wrote:Yes, I agree with Josh and Vikash...if your vehicle needs premium fuel...the owner's manual will inform the owner of that; or it will be written on the fuel door or whatever (like the Legacy Turbo)

what if it doesn't need it?
what affect will the higher octane have and will it do anything?

Legacy777 wrote: does not improve performance or fuel efficiency.

BTW, this is more ashtray material then Misc material....so I'm going to move it.

the important part was this
sounds good

subyluvr2212 wrote:

Now, in a way, you're slightly right SubaruNation. A normal engine CAN in fact benefit slightly (at least in terms of performance) with higher octane. The ECU can advance ignition timing slightly because it doesn't have to contend as much with preignition with 91 gas as it does 87 gas.

alrighty then

SubaruNation wrote: when the article stated that "higher octane fuel does nothing" that is complete Bull.

anyone take the time to read this?

i believe that this statement is inaccurate, it either does something good or bad for your engine.

if premium does nothing and it is worthless and it costs more to make and it doesn't improve fuel efficiency or power,

then WHY is it provided, and WHY do car manufacturers make cars that require it? (clearly these go hand and hand)

oh right, because it's another market for them to invest in and gain a return from.

and to advance automotive technology?
yeah because i guess thats kind of important too, with the change to diesel and hybrid and hydrogen fuels.

the post was meant to discuss weather or not this is true, not what the manual recommends.
i'll start over right now for ya,

*can cars (as a generalized topic, cars that do not require premium) benefit from using a higher octane fuel and is it worth it?

My Mazda's recommended octane is 87, but I've felt a little better response with a tank of 93 I tried. The Subaru didn't care what was put in unless it was below the recommended 87, whereupon it got pissed off.

Super Fact of the Day:

We've tested the 91 Octane gas from the 76 (conoco philips) station here in Cameron Park, CA against Sunoco 100 octane on an engine dyno.

We were building a mazda miata engine for use in the SCCA Spec Miata series. I can't remember but I think it was the 1.8L engine.

The 76 station 91 octane tested almost as good as the Sunoco race gas! I couldn't believe it!


I know it sounds all in my head, but I swear I get better gas mileage and better performance from 76 gas.

I try to avoid them, but I consistently get about 20 miles more out of a tank from Mobil/Exxon stations vs. the cheaper Hess I usually go to. Mileage seemed better with the wagon as well, but I didn't track mileage as diligently then.

i only use conoco gas b/c i get way more mpg with it than with exxon.
anybody ever used costco gas?
i swear to god they put something in it to make it cheaper.
i dont know how but i dont go as far on it and its always less expensive than anything else.

impresive, i totally believe it.
does what the gas consists of differ from state o state>

Gas also differs seasonally.

Good explanation subyluvr.

Yeah, they add stabilizers and such for the cold, which I think is just more alcohol. You don't get as far on it.

In Detroit they added water. You could see them with garden hoses in the tanks late at night. I learned to never go to the cheapest station. Luckily, I had the GL and though it was a bitch to get going in the -20 wind, it finally limped on a cylinder or two to a quality gas station where some water remover and a fresh tank of gas cleared it up in less than a minute. The new cars they had on the news expose weren't so lucky.

what the hell they add water!?
cant that kill your engine?
how did you filter out the water?