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Dave

Fuel Grades - Is Premium Better?

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unrealii posted:

 

The higher octane, the harder it is to burn the fuel. Remember that. The lower octane, the easier it is for the fuel to burn. The reason higher performance engines need higher octanes is so that the gas/air compressed mixture does not ignite before the spark comes, which is known as predetonation/knock..whatever. By using a higher octane, these engines DESIGNED FOR HIGHER OCTANE can get more engery from the gas. If a lower octane was used, the mixture would ignite from the compression, heat, or whatever else that is not the spark and slowly destroy the engine.

 

Now looking at a corolla motor, it was designed to run on 87.

 

If you put any higher octane in there, you are requiring the ignition system burn a mixture which is more resistant to burning THAN IT WAS DESIGNED FOR. That is why they say that you will not get any extra performance by using higher octane in engines which do not require it. However, there are environmental variables which we cannot control...if for some reason the engine is predetonating at 87 octane you should move up.

 

I'm not very familiar with the corolla engine, but I'm sure there is a knock sensor on there which will detect knock and retard the timing if the engine were to knock. If this was the case and you fill in a higher octane fuel, you will most likely notice an increase in performance since the engine does not have to hold itself back.

 

Lastly, I have heard rumors that some honda engines such as the v6 in the accord is designed to run on regular gas, but will actually step it's performance up if a higher octane take advantage of the higher octane. Would toyota do this...maybe....but in a corolla, I doubt it.

 

[Dave noted that Chrysler has done this in the past, going back to 1991 and maybe even earlier, with its many turbo engines - originally a rather crude system where the knock sensor was used to determine whether regular or premium was being used, and to adjust timing accordingly. The Honda engines may use a similar system - I can't think of any other way to do it.]

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well, I totally agree with you but there is a difference I have seen on my 98 (8th gen) Corolla. its not performance but visit to a gas station.

 

the way I drive:

when I fill up 87 octane, the gas tank emptys withing 2 weeks

and if I fill up 89 octane, the gas last about 3 weeks or so.

 

so I chose to do 89 since it gives me almost 150% of 87 for couple of bucks more.

 

also... when you guys fill up your corolla, how many gallon does it usually take in. Mine takes in about 10-11 gallons, 11 gallons when "fill gas damit" light is blinking..

 

but the capacity acording to specifications suppose to be 13 gallons or something.???

 

any thoughts on that?? thanks

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[Dave noted that Chrysler has done this in the past, going back to 1991 and maybe even earlier, with its many turbo engines - originally a rather crude system where the knock sensor was used to determine whether regular or premium was being used, and to adjust timing accordingly. The Honda engines may use a similar system - I can't think of any other way to do it.]

 

Ford had an even more crude system than that. On the early to mid 1980's Thunderbird Turbo Coupes there was a switch on the dash that said "Regular" at the top and "Premium" on the bottom. You had to flip it to correspond to whatever gas you had put into the car. The switch would tell the computer what parameters to use. If you accidentally set it to run on premium when you had regular in the car or visa versa, the cars didn't run correctly..

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but the capacity acording to specifications suppose to be 13 gallons or something.???

 

any thoughts on that?? thanks

 

You have a reserve of about two gallons in the tank when the "Empty" light comes on.

 

This is because the fuel pump is cooled with the fuel and will fail more quickly if it is allowed to get hot.

 

By keeping 2 gallons in the tank when the light comes on, Toyota is avoiding heating up the pump and prolonging its life.

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1zzfe only has one timing map which is optimized for emissions and to burn 87 octane fuel, the knock sensor is a safeguard in the event that knock does occur the pcm can adjust timing to compensate and keep the engine running safely.

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[Dave noted that Chrysler has done this in the past, going back to 1991 and maybe even earlier, with its many turbo engines - originally a rather crude system where the knock sensor was used to determine whether regular or premium was being used, and to adjust timing accordingly. The Honda engines may use a similar system - I can't think of any other way to do it.]

 

Ford had an even more crude system than that. On the early to mid 1980's Thunderbird Turbo Coupes there was a switch on the dash that said "Regular" at the top and "Premium" on the bottom. You had to flip it to correspond to whatever gas you had put into the car. The switch would tell the computer what parameters to use. If you accidentally set it to run on premium when you had regular in the car or visa versa, the cars didn't run correctly..

 

Toyota did that in a SCed MR2 as well. It must have been a standard thing back then.

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I've been paying for premium gas since I was 17 (about 6 years). And that's because I *had* to what with one turbo car and then another one with high compression.

 

If you

re car says it needs 87, use 87. There are 100's of studies, tests, and just plain internet results that show that putting in higher grades of fuel will do nothing for your car.

 

If you put any higher octane in there, you are requiring the ignition system burn a mixture which is more resistant to burning THAN IT WAS DESIGNED FOR. That is why they say that you will not get any extra performance by using higher octane in engines which do not require it. However, there are environmental variables which we cannot control...if for some reason the engine is predetonating at 87 octane you should move up.

 

If the car is experiencing predetonation then you have other problems that should be addressed. Putting in 93, at that point, would be like using tire sealant and believing you should go another 2k miles on said tire. Also, you're right about resistance to burn. What that means is in extremely cold climates you'll find the car might be harder to start with 93 in the car.

 

Lastly, I have heard rumors that some honda engines such as the v6 in the accord is designed to run on regular gas, but will actually step it's performance up if a higher octane take advantage of the higher octane. Would toyota do this...maybe....but in a corolla, I doubt it.

 

That's a junk rumor I've heard a lot of Honda boys tout. Believe me: If Honda, or another other car make, could get another 20HP out of their engines than they would. As mentioned here early Chrys Turbo I/II/III engines would sometimes be equipped to run into "limp modes" if you regularly used 87. But the gas mileage was much, much better if you stick 93 in those cars.

 

I know the post is old, but I scratch my head when I see people who are into car performance doing uncar-performance things to them.

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I burn Chevron 92 octane in my '03 Corolla, and I seem to get better mileage than when I previously used 89. I'm not sure of the exact difference in kilometers, but during a week's worth of driving to work on 89, I used half a tank of fuel. Switching to 92, I'm burning just below 3/4 of a tank. (a substantial improvement IMO, and worth the few cents difference in price)

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I burn Chevron 92 octane in my '03 Corolla, and I seem to get better mileage than when I previously used 89. I'm not sure of the exact difference in kilometers, but during a week's worth of driving to work on 89, I used half a tank of fuel. Switching to 92, I'm burning just below 3/4 of a tank. (a substantial improvement IMO, and worth the few cents difference in price)

 

 

I would still do more test. I don't see how the compression could take advantage of 93 pump. I'm still not convinced that the ECU software can't take advantage of 89, but I still don't put it in. I have fast cars to drive fast. I used 89 once on a road trip cause it was the same price as 87, but I couldn't tell anything on the HWY on one tank.

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I put the cheapest, lowest octane rating I can find into my car. I go thru a tank of gas so fast that even with higher mileage and less frequent fill-ups, it doesn't seem worth it to use higher octane rated fuel. I get around 30 MPG and that is me driving like I normally do (pretty agressively).

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but the capacity acording to specifications suppose to be 13 gallons or something.???

 

any thoughts on that?? thanks

 

You have a reserve of about two gallons in the tank when the "Empty" light comes on.

 

This is because the fuel pump is cooled with the fuel and will fail more quickly if it is allowed to get hot.

 

By keeping 2 gallons in the tank when the light comes on, Toyota is avoiding heating up the pump and prolonging its life.

 

ahhh, offcorse, thanks for the Info.

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This whole arguement seems a bit dumb to me. If Toyota advertises Corollas for use of regular gas (87 octane), then just use 87 octane. A higher octane resists burning more, which means that you'll most likely see a drop in your car's performance.

 

It sounds to me like MPG is the only reason you would put premium in a Corolla. The gains you get in MPG by using higher octane is most likely negated by the extra 20-30 cents per gallon you spend. Another thing I would be worried about is stalling the engine. The Corolla's engine is designed to burn a certain minimal amount of fuel for every stroke cycle of the pistons to keep it constantly moving (especially while idling). If you introduce a fuel which burns slower, then your engine's idle speed is going to logically slow down too. Think about it; that's the only possible reason why you would get better MPG from premium fuel.

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With all this octane discussion - another set of factors to keep in mind is that the recommended octane rating is based on carefully controlled conditions on a new engine. As an engine see use, how it is driven, what is the relative humidity of the driving environment, what is the average altitude of the driving environment, average ambient temperature of the driving environment, engine's state of tune, etc. will all influence the octane requirements. May have to go up or down depending on what the situation calls for. Use the 87 octane rating recommended in the owner's manual as a good first starting point for gasoline.

 

That said - don't expect a miracle gain in performance or fuel economy with a switch in octane rating. You will probably see that statistics of any apparent gain will be similar to switching to different brands of gas or filling up at a different station. Depending in on the type of driving, severe stop and go, high speed, heavy loads, etc. one may see that the engine will benefit from higher octanes to help reduce the amount of detonation. Knock sensors on these cars are pretty advanced, most of the time, you will not notice much of any drivability issue.

 

Also, don't read into that idea that higher octanes are "harder" to burn than lower octanes - that might be the wrong word for it, as it invites too wide of an interpretation. Think more on the lines of the higher octane rating represents decreasing sensitivity to pressure and heat, delaying ignition. Premium or Regular - it will all burn the same way, only difference is its resistance to ignition from non-specific sources (sources other than the spark plug - the primary source of ignition). In other words, think of higher octane fuels as having a better chance for igniting more "accurately" than regular octane fuels. That doesn't mean stop by a race track and pump in the 110-118 octane race gas (most are "leaded" gas anyways) - there you are running beyond what the engine was envisioned to run on.

 

Not uncommon for older cars to use gas that is 3-6 numbers higher in octane than when new - just a function of carbon buildup (similar effect to decreasing combustion chamber volume or raising compression ratio). Higher average temperatures, hotter running engines, low humidity and a lower altitudes all require bumping the octane to keep the engine from detonating. Some just tend to get better MPG with mid to premium fuels (due to age, mileage, driving conditions, etc.).

 

Bottom line - pump in stuff that you feel is best, works well, and fits your budget. No worries.

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This whole arguement seems a bit dumb to me. If Toyota advertises Corollas for use of regular gas (87 octane), then just use 87 octane. A higher octane resists burning more, which means that you'll most likely see a drop in your car's performance.

 

It sounds to me like MPG is the only reason you would put premium in a Corolla. The gains you get in MPG by using higher octane is most likely negated by the extra 20-30 cents per gallon you spend. Another thing I would be worried about is stalling the engine. The Corolla's engine is designed to burn a certain minimal amount of fuel for every stroke cycle of the pistons to keep it constantly moving (especially while idling). If you introduce a fuel which burns slower, then your engine's idle speed is going to logically slow down too. Think about it; that's the only possible reason why you would get better MPG from premium fuel.

 

87 pump has a lower flash point then higher octane fuels. The car can and will run on 87, but because the ECU is going to try and optimize timing and the ECU has no ideal what fuel is in the tank, I still think the car could take advantage of 89 over time. It wouldn't happen over night tho, because the ECU should slowly try and optimize the cars tune. 91,93 would be a complete wast because the car doesn't have the compression for it. Why do you think the car would stall? That's just silly. It's still gasoline. Depending on how the ECU was programmed, 89 could get more gas, if the injector pulse length could be shorter from having a higher flash point fuel.

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Don't forget that using a higher octane fuel in your car also has a psychological advantage.

Whether it is true or not - you feel like you are helping your car to run better.

Those extra pennies per gallon and maybe a few more miles per gallon makes you feel like it is a good deal.

For all those using higher octane fuels in your cars - keep on smiling!

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