05 Avalon Fuel Recommendation

[preskev]

05 Limited - Getting 36.4 mpg is pretty impressive. Toyota seems to pretty conservative on their performance estimates for this car. I read in Car and Driver this month, which Avalon won the 30,000 Touring Sedan shoot-out, the Avalon posted a 6.0 on the 0-60 test. I believe the advertised 0-60 was 6.5.

I am curious, being an engineer, since the car seems to handle all octane levels that there maybe something more then just the immediate pinging the operator may experience using a lower level octane. If the engine and computer were calibrated to the 91 octane, and you use the 87 or 89 for a considerable amount of time. I wonder if the risk of gunk build-up in the engine rises with the lower octane levels. I guess only time will tell. My 2 cents.

[johnd]

05,

Thanks for the report. Before I forget it, I guess the graduation also makes for happy in your wallet. I've got a friend says that if he ever gets his last two out of college, he will begin to live in 'high cotton'.
Your trip sounds like the last one I had in my Volvo. Had a slow, long steady climb from the plains to top of a mountain pass, then very fast drop down to a lower alt. Going out MPG wasn't impressive. But coming back it was great. 26mpg vs 33.
I'm not getting what I expected, but it is fair. To date, with 4 fillups, I've gotten a grand total of 26.5mpg. It has varied starting at 22.6 up to 28.3. One good thing, it has gone from the first tank of 22.58mpg to 26.99, to 27.0 to 28.3. Good trend. This has all been on 87 oct. ( in my Volvo, over 68k miles, got 26.7mpg)
Glad you confirmed what all of my past test over the years have proven to me, that hi-test gives no better than reg. Many years ago Consumer Report did a test, found the same.

Preskev, I don't think the low oct hurts the car at all. The Volvo stated it preferred hi-test but would run ok on regular. The 7 years I had it, it only had one tank of hi-test and it was running like a jewel when I traded it in. Yes, I did run injector cleaner through it a couple of times, but saw no change in performance before nor after. Never had a single ping from it.
As you probably know, pings can come from carbon deposits in the cly. head, but that can accumulate from other than low octane.
In P-51s, we use to 'blow out' the carbon every 30 minutes at cruise. First time I did it at night scared the hell out of me, thought the aircraft was on fire!
I take it that you have recieved your cd-rom from Toyota? Does help some in figuring out this machine.

[05Limited]

Originally Posted by preskev

05 Limited - Getting 36.4 mpg is pretty impressive. Toyota seems to pretty conservative on their performance estimates for this car. I read in Car and Driver this month, which Avalon won the 30,000 Touring Sedan shoot-out, the Avalon posted a 6.0 on the 0-60 test. I believe the advertised 0-60 was 6.5.

I am curious, being an engineer, since the car seems to handle all octane levels that there maybe something more then just the immediate pinging the operator may experience using a lower level octane. If the engine and computer were calibrated to the 91 octane, and you use the 87 or 89 for a considerable amount of time. I wonder if the risk of gunk build-up in the engine rises with the lower octane levels. I guess only time will tell. My 2 cents.

You may be correct and if you are that should be part of the explanation that Toyota should give us in the manual. I'm not any kind of expert on this nor should we have to be to read the owners manual. On the back cover of the 05 manual it says you can use 87 octane before it starts that mumbo jumbo about research octane. They know what the heck is provided at the pump so they just need to say plain and simple what grade to use.

[05Limited]

After I posted the above message I decided to send an email to Toyota to see what fuel we should be using and this FAQ screen came up so I captured the below message for all to see. I did not see what the "*" was suppose to mean. I clicked the current model year and it did say 2005.

TOYOTA FAQ SECTION:

You can find the recommended fuel octane rating for your vehicle on the back cover of your Owner's Manual.


Our current model year vehicles have the following unleaded fuel octane rating recommendations: MODELOCTANE4Runner 87*Avalon 87*Camry 4 Cylinder

87 V6 87*

[05Limited]

Toyota's answer to the octane fuel requirements on the 05 Avalon:


SubjectFuel Requirements for 05 Avalon Discussion Thread Response (James)06/16/2005 11:05 AMThank you for contacting Toyota Motor Sales, U.S.A., Inc.

We apologize for any confusion regarding Toyota's premium fuel recommendation for the 2005 Avalon.

Per the 2005 Avalon Owner's Manual:

Fuel type:
Unleaded gasoline, Octane Rating 87
(Research Octane Number 91) or higher.
For improved vehicle performance, the
use of premium unleaded gasoline with
an Octane Rating of 91 (Research Octane
Number 96) or higher is recommended.

The engine will run properly on 87 octane gasoline. Using 91 octane gasoline, the engine will have improved torque and responsiveness as a result of the higher octane fuel; it will not have improved fuel economy.

[jchiu]

Here’s my two cents worth (maybe it sound be a nickels worth with inflation).



Octane is the resistance of a fuel to knock. Knock is when the fuel self ignites and causes a very high pressure rise in the combustion chamber. This pressure rise creates a pressure wave, which reverberates through the combustion chamber. The "pinging" that you hear is the pressure wave hitting the combustion chamber wall, reflecting off the wall, hitting another part of the wall, and repeating. The pressure wave is moving at the speed of sound, so it sounds like shaking a can of marbles. For those of you who understand audio frequencies, it can reverberate at approximately 5-9 kHz, which is much faster than the typical engine noise, approximately 10-50 Hz.



There are two methods to determine octane, a motor octane number (MON) and a research octane number (RON). What you see at the pump is the average of the two (R+M)/2. The MON is a high rpm and high load test condition. The RON is a low rpm and low load test condition. In both tests, the candidate fuel is compared to a reference fuel. Typically, the motor octane number is lower.



Fuel is typically transported in pipelines. The fuel that a refiner puts into the pipeline at a location typically conforms to an American Society for Testing and Materials (ASTM) specification The fuel that the refiner pulls back out at another location may be the fuel that the refiner put in or (a more typical situation) may be a fuel of the same type that another refiner put in. This is called fungible fuel. The difference in the brands (Shell, Exxon, Chevron, etc.) is the additives that are added to the tanker (after the fuel has been pulled out of the pipeline). Some fuels are tracked through the pipeline (Amoco Clear for example) and the exact fuel that was put in is pulled back out. Typically, there are two octanes for fuels, 87 and 91 (high altitude places may have lower octane fuels). Mid-grade fuels (89 octane) are made by a 50:50 mixture of 87 and 91 octane fuels. Higher octane fuels (93 octane) are made using octane improvers to the 91 octane fuel. Since different fuels are carried by the pipeline, there is some mixing, but this is minimized by creating the correct flow dynamics. The mixed fuel is not delivered to gas stations.



Most modern cars have knock sensors. A properly working knock detection system will detect knock and retard timing (which lowers the tendency to knock) before you can hear it. You may never hear knock even though the fuel you are using is letting your engine knock. You may feel a loss in power when timing is retarded (to be politically correct, should I say timing challenged?).



So what does all this mean? Typically, under normal driving conditions, your car shouldn’t knock on the low octane fuel, and you will not see a fuel economy difference between a regular and premium fuel. Under spirited driving conditions, you car may knock on the lower octane fuel, and you may feel a power loss, but it is not detrimental to your engine since you have knock detection.

James

[Jaggrey]

wow that was a good breakdown