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Discussion Starter · #1 ·
Hi all:

I bought a touring elite a week ago. I am wondering the type of gasoline to put in the tank. As I research a little more; it just gets more and more confusion.
2011 Honda Odyssey Touring Elite vs. 2011 Toyota Sienna XLE Comparison Test
It states that
+87 is acceptable and +91 for best performance.

I thought adding a +91 fuel gasoline into an engine that's designed for +87 won't actually do anything at all so I am just wondering why they make such claim. If that's true, does that have to do driving habits?

I don't expect it makes a difference on 5 or 6 speed transmission but I am definitely not mechanically sound enough to make such claim.

Just curious.
 

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I'd go by the owner's manual. Page 540 of the manual says:

"Your vehicle is designed to operate
on unleaded gasoline with a pump
octane number of 87 or higher. Use
of a lower octane gasoline can cause
a persistent, heavy, metallic rapping
noise that can lead to engine damage."

There is no separate manual (or instruction) for the "Elite" model so I assume a minimum of 87. Anything lower can cause engine damage. Anything higher, won't.
 

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Running our Touring on 87 octane from Costco. Runs smooth and quiet for us.
 

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They make the claim because the PCM is designed to adjust to any fuel put in it. The only thing is you won't make up the difference in cost of gasoline in increased mileage.
 

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Discussion Starter · #5 ·
So are you saying that putting in a higher octane rating fuel would improve the mpg in this type of Engine? I can understand how it would impact mpg if one puts +87 fuel into an engine designed for +91 due to knocking.

Maybe I should just use the +89

Please excuse my lack of mechanical knowledge and thanks for all the comments.
 

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Running a higher octane will either do nothing or possibly lower your HP a touch. Octane is the rating against detonation, not the energy potential of the fuel. Just like a higher ethonal mix in gas ups the octane but doesn't increase the HP.

The only way you could take advantage of the higher octane is if the ECU is able to increase timing but even that will have a limit since the compression ratio and everything else is the same. The ECU is more designed to account for a fuel of lesser octane and retard the timing to account for it.

Its why the Prelude could run on 89 even though I would recommend it as with its 10:1 compression, VTEC, and timing it was designed for 92+ octane

Sent from my GT-I9000 using AutoGuide App
 

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Oh.. forgot the main point.. higher octane = slower burn. So if you run higher than you need you get a slower burn and a reduced energy output

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Running a higher octane will either do nothing or possibly lower your HP a touch. Octane is the rating against detonation, not the energy potential of the fuel. Just like a higher ethonal mix in gas ups the octane but doesn't increase the HP.

The only way you could take advantage of the higher octane is if the ECU is able to increase timing but even that will have a limit since the compression ratio and everything else is the same. The ECU is more designed to account for a fuel of lesser octane and retard the timing to account for it.

Its why the Prelude could run on 89 even though I would recommend it as with its 10:1 compression, VTEC, and timing it was designed for 92+ octane

Sent from my GT-I9000 using AutoGuide App
What does "increase timing" mean? Did you mean advance the timing?

My understanding is this. In vehicles with a recommended octane of 91 (Anti Knock Index or AKI), if you use a lower octane fuel, the ECU will adjust the timing to try and avoid pre detonation commonly referred to as "knock". This has the effect of reducing power and mileage, so while you'll save on gas, your fuel economy will be poorer so you don't really save anything. In addition, if you put the engine under "lugging" loads regularly, the ECU may not have the range available to it to completely avoid pre detonation and you can cause engine damage.

On an engine designed to operate with 89 octane, adding a higher octane does nothing as there was no knock with 89 and will be no knock with 92. The ECU isn't programmed to advance or retard the timing in that case and in any event a higher octane fuel doesn't contain any more energy than 89 so you are just paying more for fuel that doesn't benefit you.

As I suggested above, following the direction in the owner's manual is the best advice one can give here.
 

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What does "increase timing" mean? Did you mean advance the timing?

My understanding is this. In vehicles with a recommended octane of 91 (Anti Knock Index or AKI), if you use a lower octane fuel, the ECU will adjust the timing to try and avoid pre detonation commonly referred to as "knock". This has the effect of reducing power and mileage, so while you'll save on gas, your fuel economy will be poorer so you don't really save anything. In addition, if you put the engine under "lugging" loads regularly, the ECU may not have the range available to it to completely avoid pre detonation and you can cause engine damage.

On an engine designed to operate with 89 octane, adding a higher octane does nothing as there was no knock with 89 and will be no knock with 92. The ECU isn't programmed to advance or retard the timing in that case and in any event a higher octane fuel doesn't contain any more energy than 89 so you are just paying more for fuel that doesn't benefit you.

As I suggested above, following the direction in the owner's manual is the best advice one can give here.
correct.

modern vehicles will generally retard timing to adjust for lower octane fuel as much as they can.

putting a higher octane in does pretty much nothing. while most people 'claim' to see increased fuel economy, realistically there's another factor causing the change (normally that they're subconsciously changing their driving habits).

If you manual says 87... use 87. if it says premium... use premium.

I'll give you a hint: there are very few Hondas that recommend anything other than regular. I think it's pretty much limited to the Civic Si and the FCX that don't recommend regular unleaded. Acuras on the other hand... tend to be premium or mid-grade gas.
 

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When I had the 2000 Ody I used 87 Octane, I put over 95000 miles on it and no problems. The manual said you use 87, but with higher Octane you would get 5 more horsepower. Maybe some that still have a 2000 manual can verifiy this.
 

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I use 87 Octane as well. I tried a full tank of premium, no change in fuel econ.

With that said, with my 1995 maxima, I did get better fuel economy by running it on premium so I kept using that. (i can't remember at this time what that engine was designed to run on).
 

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... Running a higher octane will either do nothing or possibly lower your HP a touch...
Absolutely not. If that was the case, the whole
racing world would save billions, instead of using
the much expensive 100 plus octane gas. So you
are saying they would get more horse power with
a lower octane gas? Not.

I only use Shell 91 in my cars, cause here in Ontario
it is the only gas Ethanol free, besides having the highest
octane rating.
 

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Absolutely not. If that was the case, the whole
racing world would save billions, instead of using
the much expensive 100 plus octane gas. So you
are saying they would get more horse power with
a lower octane gas? Not.

I only use Shell 91 in my cars, cause here in Ontario
it is the only gas Ethanol free, besides having the highest
octane rating.
I think the point you might be missing is those race cars running 100+ octane have engines designed to produce maximum horsepower with a particular timing set up and usually much higher compression ratios. If they didn't have high octane fuel, something would have to "give", perhaps a lower compression ratio which would result in lower combustion force and less HP output.

I think we can all agree that putting a lower octane in those cars would reduce power as the ecu would have to retard the timing or suffer engine damage from pre detonation (ping) of the fuel/air mixture. But putting high octane fuel in a car that doesn't have an engine to take advantage of it won't provide extra HP and is just a waste of money.

Try reading this:

Premium Fuel - Do You Really Need High Octane Gasoline?
 

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When I had the 2000 Ody I used 87 Octane, I put over 95000 miles on it and no problems. The manual said you use 87, but with higher Octane you would get 5 more horsepower. Maybe some that still have a 2000 manual can verifiy this.
Yeah, our '99 said something like that. You can run on 87, but if you want all the HP, you need to bump up to premium.

I think the point you might be missing...
...is that the Ody is one of those vehicles that DOES gian hp when you use premium.
 

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Yeah, our '99 said something like that. You can run on 87, but if you want all the HP, you need to bump up to premium.


...is that the Ody is one of those vehicles that DOES gian hp when you use premium.
I would run only 87 regular octane in it. I believe the Honda 3.5L you will gain 5 to 10 horse by using 91 octane+, it will take a few tank fulls for the computer to adjust, but you most likely never going to notice the 5 to 10 horse gain in this 4500 pound vehicle.

I remember in my older Pilot, the owners manual said to use higher octane if pulling/towing a heavy load or something to that effect.
 

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What does "increase timing" mean? Did you mean advance the timing?

My understanding is this. In vehicles with a recommended octane of 91 (Anti Knock Index or AKI), if you use a lower octane fuel, the ECU will adjust the timing to try and avoid pre detonation commonly referred to as "knock". This has the effect of reducing power and mileage, so while you'll save on gas, your fuel economy will be poorer so you don't really save anything. In addition, if you put the engine under "lugging" loads regularly, the ECU may not have the range available to it to completely avoid pre detonation and you can cause engine damage.

On an engine designed to operate with 89 octane, adding a higher octane does nothing as there was no knock with 89 and will be no knock with 92. The ECU isn't programmed to advance or retard the timing in that case and in any event a higher octane fuel doesn't contain any more energy than 89 so you are just paying more for fuel that doesn't benefit you.

As I suggested above, following the direction in the owner's manual is the best advice one can give here.
Depends on the car... Some cars the computer (ECU) will notice and advance or retard the timing, adjusting for higher octane, I believe the Honda 3.5L will.. On my previous post, on an older Pilot I had, the owners manual from my recollection said to use higher octane when towing or carrying a heavy load...

I agree, to just use the 87 octane in the Oddy and save your $$.

On a side note, on come cars you can have them "Tuned" like I had my Corvette. The tune alone added 20 horsepower at the rear wheels on the dyno using the same 91+ octane that was recommended. That said, you can only notice the extra 20hp if you are hard on the gas, since the car already had 400 horse stock.
 

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I use regular 87.
Even the service department at the dealer recommends that I just use regular.
 
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