Is premium fuel really necessary?

[cruiser73]

I have a 1999 Aurora with 89000 miles, and it runs just perfect. I've only owned it a few months.

I know that the manual states to use premium fuel. The owner I bought the car from said that he always used mid-grade gas, which is typically 89 octane.

Since I have owned it, I probably have only put 4 or 5 tanks of fuel in it, and I too have used the 89 octane "plus" or "mid-grade" fuel.

It runs perfectly, and I have not had any pinging, run-on, hesitation, or anything.

I was wondering if any of you have had any problems with NOT using premium fuel in your stock 1st gen Auroras?

I'm not worried about losing a little bit of power due to the computer retarding the timing a bit for the lower octane fuel, I'm just wondering about any problems.

Has anybody tried using "regular" unleaded, 87 octane? How did that work out?

Thanks!

[Marc]

From what I have seen firsthand & from what I have read, all Auroras will run better on premium.

[Deleted]

oohhh boy I smell a fuel war. I ran regular octane in my aurora for almost a year. Premium every once in a while. Car never ran bad and I could never notice loss of power compared to premium. Still managed about 27-33 mpg on long trips.

[XJSman89]

Not this again! Yes it probably runs fine on mid grade because it is a mix of unleaded and premium. It will run better with higher octane gas. Don't run unleaded. Why would you risk paying for a costly repair to save a dollar or two at the pump? Think of it like insurance. They wouldn't tell you it needs premium without a reason.

[sall]

Run Premium, 91+. Lower than 91 and you risk knocking. If in an emergency you can use as low as 87 Octane IF no knocking occurs. If you don't use 91 you can and may fail an emissions test. Don't believe me read the owner's manual.

I won't state my opinion only factual information in this regard. There is a lot of info on this posted everywhere online about detonation/knocking/retarding. Ageless debate.

[jprice90]

WELL..
i fail..

i only put about 5 gallons of premium in my car when i 1st bought, i was told there wasnt a diff, so i always used unleaded from then on, but NOW that i know that it can really mess the car up, it's mid grade for now on, hopefully this thread didnt jynx me and mess my car up , it's been running great though..

[oldsmobile99]

for the past couple months ive only been running regular. the only thing ive noticed diffrent with the car is, not as much power and dosent run as smooth, and also a decrease in mileage.

[jprice90]

Feb 23, 2010 18:02:15 GMT -6 oldsmobile99 said:

for the past couple months ive only been running regular. the only thing ive noticed diffrent with the car is, not as much power and dosent run as smooth, and also a decrease in mileage.

yup, exactly
never really thought about it, but since you said it..lol

[Marc]

With 10.3:1 compression & using 87 or 89, the PCM is going to retard the timing very far back......bottom line, big drop in power.

[jprice90]

it just hasnt been done yet
cant you tell when the PCM is retarded?

[sall]

lol... was that a joke or a lack of understanding of timing? retard is the opposite of advance.

Burning fuel with a lower octane rating than required by the engine often reduces power output and efficiency one way or another. If the engine begins to detonate (knock), that reduces power and efficiency for the reasons stated above. Many modern car engines feature a knock sensor – a small piezoelectric microphone which detects knock, and then sends a signal to the engine control unit to retard the ignition timing. Retarding the ignition timing reduces the tendency to detonate, but also reduces power output and fuel efficiency.

[jprice90]

no i knew what that was, just didnt know exactly what will happen, so instead of knocking, the sensor sends a signal to the ecu, ecu retards timing but the engine doesnt knock

i just wanna get this old #$#@ out so i can put a tank of good stuff in..poor Rora

[jprice90]

sooo i tryed to run all that unleaded crap out, and put $15 super in, i dont do alot of driving so it's usually just $10-15 every now and then lol, man it feels so much better lol, like it has a little bit more power or pickup, weird

[Marc]

When you use premium, the PCM allows more spark advance.
More spark advance = more power, up to the point where knock starts.

[dens95olds]

My car stumbles, backfires when i don't use premium. Once, i filled up in a Union76 premium, but they had a warning saying that the gas may have ethanol or some kind of nol, and it stumbled until i ran a bottle of techron. So, I don't know, I think it does need premium and a clean premium at that.

[intheb0x]

ethanol is allmost in all our gas now, most of it is 10%, but they were trying to mandate it to 15-25%, which kills our motors and small engines.
ethanol is CRAP, its less efficient and more dirty for the environment then regular gas..

in some state they were trying to mandate a higher % of it and Chrysler said it would not be honoring its car warranties if it happened, goes to show u what it does to cars that arent supose to use it..

here its 10% in all gas, i never noticed a change BUT if i see a ethanol free station(a dying breed btw) i always stop even if im broke.. it equates to better MPG and more power...

like i said ethanol is a joke and far from a efficent "renewable" source of energy, all its doing is making people pockets fat fat fat, and they lobby for it, thats why 10% is already mandated here and in many other states and they are trying to bump that up to 15-25% in a few years..

[jprice90]

thanks for that info, i'll keep my eye out for that crap/any signs
i dont recall seeing any though, but im sure i will soon

[drivenmad]

I had troubles when I first bought my Aurora, because the previous owner used 87 octane. The throttle would click and sound like it had a blow off valve. I also had problems with it idling too high in warm weather or too low in colder weather. I switched to 93 octane from BP and after the second fill up (after the rest of the 87 was out of the tank) everything ran properly. But, I think I'm the only one who has experienced this. But like everyone says, if the manual says to use Premium, use it.

[therev]

If its a .$30 increase from 87 to 93, That factors out to a little over 5 bucks a tank. I wouldn't it.

If it helps, I get 24.1mpg for a tank on 93, and I got 22.3 running 87 (first tank had 87 in it)

[soggytom]

Around here, it's typically an extra $.20 a gallon. And no, the higher mileage probably won't offset the higher cost. But it's worth it to me knowing the knock sensors and the computers are melting down trying to keep the engine from exploding just because I wanted to save a couple bucks.
With a full tank costing $58 today (March 18), the extra $4.00 is worth it. If I were a total road warrior- well, I'd be driving something much more efficient and reliable, anyway. ;D

[scottydl]

This dispute never comes to any REAL conclusions. A lot of people throw out "well I tried this" and "I did this for 1 tank and here's what happened" ... the truth is you'd need a very controlled environment and guarantee that your driving style doesn't change to really tell if the premium makes a noticeable difference.

I ran 89-90 octane mid grade for the majority of the 5+ years I owned my Aurora, with no engine problems whatsoever. I did a somewhat scientific trial of premium for 6 months straight (there's a thread about it around here somewhere), and I noticed NO significant improvement in performance or fuel economy.

READ THE OWNER'S MANUAL. It says that 87 Unleaded is required, and 91+ Premuim is recommended. You may notice a decrease in performance/acceleration when using 87 octane, the manual will say. I know the fuel gauge and tank filler cap sound more sinister with the statement "Premium Unleaded Fuel Only" but obviously the car will run on anything sold at a gas pump in the United States. This car is smart... the knock sensors will alter the timing if you are using lower grade fuel, so chances are high you'll never notice a real difference.

[sall]

Mar 18, 2010 12:14:43 GMT -6 scottydl said:

READ THE OWNER'S MANUAL. It says that 87 Unleaded is required, and 91+ Premium is recommended. You may notice a decrease in performance/acceleration when using 87 octane, the manual will say. I know the fuel gauge and tank filler cap sound more sinister with the statement "Premium Unleaded Fuel Only" but obviously the car will run on anything sold at a gas pump in the United States. This car is smart... the knock sensors will alter the timing if you are using lower grade fuel, so chances are high you'll never notice a real difference.

I beg to differ.

Verbatim from 1996 manual.

Fuel:

Use premium unleaded gasoline rated at 91 octane or higher. At a minimum, it should meet Specifications ASTM D4814 in the United States and CGSB 3.5-M93 in Canada. Improved gasoline specifications have been developed by the American Automobile Manufacturers Association (AAMA) for better vehicle performance and engine protection. Gasolines meeting the AAMA specification
could provide improved driveability and emission control system protection compared to other gasolines.

Be sure the posted octane for premium is at least 91. If the octane is less than 91, you may get a heavy knocking noise when you drive. (In an emergency, you may be able to use a lower octane -- as low as 87 -- if heavy knocking does not occur.) If you’re using 91 or higher octane unleaded gasoline and you still hear heavy knocking, your engine needs service.

If your vehicle is certified to meet California Emission Standards (indicated on the underhood tune-up label), it is designed to operate on fuels that meet California specifications. If such fuels are not available in states adopting California emissions standards, your vehicle will operate satisfactorily on fuels meeting federal specifications, but emission control system performance may be affected. The malfunction indicator lamp on your instrument panel may turn on and/or your vehicle may fail a smog-check test. If this occurs, return to authorized Aurora retailer for diagnosis to determine the cause of failure. In the event it is determined that the
cause of the condition is the type of fuels used, repairs may not be covered by your warranty.

Some Canadian gasolines contain an octane enhancing additive called methlycyclopentadienyl manganese tricarbonyl (MMT). If such fuels are used, your emission control system performance may be affected. The malfunction indicator lamp on your instrument panel may turn on. If this occurs, return to your authorized Aurora retailer for service.

To provide cleaner air, all gasolines are now required to contain additives that will help prevent deposits from forming in your engine and fuel system, allowing your emission control system to function properly. Therefore, you should not have to add anything to the fuel. In addition, gasolines containing oxygenates, such as ethers
and ethanol, and reformulated gasolines may be available in your area to help clean the air. General Motors recommends that you use these gasolines if they comply with the specifications described earlier.


There are the facts. Maybe the owner's manuals differ between the years.

[aldrichd]

Don't forget that first generation Auroras are to use 91 octane or higher for best performance and 2nd generation Auroras are NOT regulated to 91 octane.

[governor]

I cross the border in to the U.S. and you guys are lucky. Your most premium is (like mentioned above), .15 - .30 more a gallon. That equates to roughly .04 to .07 more a liter for Canadians - wow! In Canada, the most premium is a bloody .12 or .13 a liter more!! That equates to .50 + more a gallon! For some reason premium fuel is double the extra here in Canada - we are getting ripped!
We can't get 93 octane any more, only 91 or 94(second mortgage required for Sunoco 94).
This is why Canadians hate fueling up with premium. I wait until Thursday's when Ultramar 91 is .03 less a liter for premium..

[soggytom]

There's also the subtle differences between the 95-97 and 98-99 models. Perhaps the later ones deal better with cheap gas?

[scottydl]

The '99 manual is indeed worded differently, with these statements...

Use premium unleaded gasoline rated at 91 octane or higher for best performance. You may use middle grade or regular unleaded gasolines, but your vehicle may not accelerate as well. . . Be sure the posted octane for premium is at least 91 (at least 89 for middle grade and 87 for regular). If the octane is less than 87, you may get a heavy knocking noise when you drive. If it’s bad enough, it can damage your engine.

So it really only condemns octane under 87, which I've never even seen for sale. There ARE some differences over the years of Classic models, but they all used the same engine and fuel systems from what I understand. I think it's more likely that the knowledge of how the Classic's 4.0L engine manages fuel improved as the years went by. Under that theory, the '99 manual would be the most up-to-date on that issue and many others that the Classics share.

Mar 7, 2010 18:32:17 GMT -6 drivenmad said:

I had troubles when I first bought my Aurora, because the previous owner used 87 octane.

These are the statements that can be a little misleading. Perhaps the previous owner used really low quality budget gasoline, without the standard detergents that reputable gas stations offer. But it seems unlikely that using 87 octane alone would cause engine damage.

[lanceslambos]

a lot of people don't know that Casey's was the first gas station to start mixing ethanol in their gas back when the classic Auroras were being produced. from what i've read it takes 2 or 3 (maybe more ) gallons of oil to produce 1 gallon of ethanol. so in reality it makes no sense as a "greener" fuel. it's making the rich richer and that's why they are really pushing it, not cause it's more economical at all. when i first got my Aurora i paid close attention to my mpg when i would fill up with premium and 87 and according to my experience its worth the extra 10 - 20 cents a gallon for the extra miles the car achieved on premium. i also figure that if 87 consistently ran that much worse, what was it doing to the sensors and so on. i have never in my life seen any gas that was rated below 87 octane.

it's pretty hard to find anything above 91 octane around these parts unless i want to pay 6 bucks a gallon for cam2 which is either 100 or 110 octane. as far as mid grade goes; i never noticed a difference in performance or fuel mileage between mid and premium but from mid to low grade the difference was small. i also heard from mechanics that as the engine gets more wear that the compression slightly drops and thereby mid grade would suffice as premium.

[soggytom]

That makes sense, as the engine ages and wears. It seems to me the evolution is similar to that of the Ford Mod Motor- early versions use premium, leak like sieves and are crazy expensive to maintain. After a couple years, some subtle updates (plug wires, etc.) cure most of that. Then, an overhaul involving a switch to coil-on-plug and ability to run on regular. Oh, and no more leaks.

So, I stand by premium on 95-97s, probably mid on 98-99s, then regular on the Gen2s.

[parks]

Just to add another wrinkle.

I live at 7500 feet and have always heard at high altitude you can use a lower octane.
I found this at popular Mechanics Q & A.

Octane is the ability of a fuel to resist knock, and high-compression engines tend to knock more. The obverse of that is that lower-compression engines can run on lower-octane gas. Air is thinner the higher above sea level you go. Less air going into the cylinders means less pressure at top dead center when things go bang. It’s a lot like lowering the compression ratio in the engine, reducing the need for high octane. Cars will run just fine on lower-octane fuel when they’re well above sea level—and all of those states are. Hopefully, by the time you get back down to denser air, you’ve burned off most of the low-octane stuff, and can refill the tank with higher-grade fuel.

cheers

[Marc]

Mar 19, 2010 18:03:27 GMT -6 parks said:

Just to add another wrinkle.

I live at 7500 feet and have always heard at high altitude you can use a lower octane.

Because of the fact that the higher you go, the thinner the air gets. And if the fuel system is set for a lower altitude, the higher you go, the richer the fuel/air mix gets. A richer fuel/air mix will surpress knock better than an even or lean mix.