why does the 2004 Totota Avalon use high test gas

Evidently the compression is higher than the regular gas engines. If the octane is too low, you will have pinging if the anti knock sensors can't handle it. It will sound like a knocking sound when you get on it. Not good for the engine.

When you use high octanes in gas, you pay more, but people say than you could run more kilometers for the same quantity (in gallons) of gas. Could that be true?

I strongly doubt it. A chemical to reduce knocking has replaced a small amount of the gasoline, so there is slightly less gas per gallon to burn. If anything, that might lower your MPG. It would probably take lab equipment to measure the difference either way.

No.

People *want* it to be true, but it's not true. Octane is not a "power booster" that gives you "more energy". It's simply an indicator of the fuel's ability to resist pre-ignition.

Now, will a lower octane fuel cause lower gas mileage in some cars? Possibly. But that's not because higher octane fuel is "better" or "contains more energy".

El 19/10/14 a las 18:05, Elmo P. Shagnasty escribió:

Thank you, both. Another popular myth.

You are reading your manual incorrectly. I have a 2004 Toyota Avalon XLE and it says Regular octane 87 is required and Premium octane 91 is recommended for higher performance. I've been using Regular fuel ever since I've owned it.

I haven't checked for that in my manual, but that's how my car runs. It definitely seems to take advantage of the higher octane gas by adjusting the timing. "variable valve timing". I can tell the difference between regular and premium. Not huge mind you, but there is a difference. It shows the most on hilly terrain and such with a loaded car. And seems a little more perky around town, but not hugely so. It also idles smoother with premium than regular. I wouldn't expect a difference there, but it does idle smoother on the good gas. I can switch grades back and forth and see the difference. It's OK on regular, but purrs like a sewing machine with premium. There is less vibration. But due to the knock sensors and such, and variable valve timing, it does not ping or knock on any grade of gas.

No, I don't think so. I don't seem to get any better mpg on premium. At least not enough to notice, and I track my highway mpg real close when I drive to my dirt patch. The engine just runs smoother, and seems more perky on premium than regular once the timing adjusts for the change.

What really happens is the knock sensors detect knock and the computer retards the ignition timing, not the valve timing.

Here's a challenge if you want to take the time to try it. My test tend to show that if the car wants premium, but you feed it regular, then it will retard the timing to avoid damage to the engine. You might not feel the loss in performance, but it is there. The challenge is to run several tanks of premium and calculate the Cost Per Mile and see if the cost per mile actually goes down. Here's the reasoning, if you get 20 mpg with gas that costs $3.50, then your cost per mile is $0.175 (3.50 / 20 = 0.175), but if you put in premium that costs $3.70 but the mileage goes to 23, then 3.70 /

23 = $0.161. The cost per mile in this case is 0.014 less. Not much, but if you drive 10,000 and save 0.014 per mile, then you save $140 per year with the more costly fuel. It only cost more to buy, but if the mileage improves as a result then it costs less to use, and the savings over a year is $140, more if you drive more.

My car, a '94 BMW, wants to be fed the mid-grade fuel, but I fill at Costco and I can get premium for the same price as the mid-grade at the gas station down the street. Since my car only calls for the mid-grade, then I probably get little to no benefit of premium, but the price is the same so I do it. If I go to the gas station, I get mid-grade because my car gives better mileage than with regular, so the cost per mile with the mid-grade is lower. Your pricing will be different, but you can still calculate the cost per mile. All you do is calculate the mileage, then use the result to divide into the price of your gas. Your mileage remains the same regardless of the price of gas, although the price of gas changes almost daily, so you should keep track of the price of regular and divide a previous mileage calculation into current pricing so you can compare what savings might exist with the premium.

For example, if you bought regular three weeks ago at $3.40, and today it costs $3.50, then your savings spread will be different because when regular is 3.40, premium is 3.60 on that day, but the result on that day is still a difference of $0.014, so While the premium costs more to fill the tank, it takes you further so the actual cost is lower by about 1.4 cents per mile.

If your car calls for premium but tolerates regular, then you are not hurting anything, but your decision tyo cheap out on the fuel might actually cost you more. Try it on a few tanks and see what happens, I think you will be pleasantly surprised.

Yes, it absolutely can be true. It might not be true in all cases, but it's worth the try in your own car to see how the numbers shake out. As the price of a gallon of gas goes up, the spread actually improves the calculation.

If regular costs 3.50 and premium is .20 more, 3.70 but gives an added 3 mpg, then assuming regular gives 20 mpg, then it costs .175 per mile, but premium at 23 mpg costs .161 per mile, or 0.014 less per mile. If regular is

3.80 and premium is 4.00, then regular costs 0.190 per mile while premium is 0.174, this is 0.016 lower cost per mile.

Not only can premium cost less per mile, it costs less on an upward sliding scale as the price of gas goes up. You have to do the math for your car, but my example of a 3 mpg improvement is not out of line, so the savings I illustrate are real. Your savings will depend on what mileage you get with regular and premium.

If indeed it did detect knock that would happen, but my car does have variable valve timing, and it adjusts constantly for the type of driving, and evidently the grade of fuel also, being as I see a difference. I think about the same as "Vtec" in Honda talk..

Of course.

Mine actually calls for 89 octane if I remember right. I'd have to check the manual. But, basically regular, except that real world regular tends to be rated 87 octane and 2 less than what Toyota is calling for.

They don't call for premium for mine. Mine also seems to see most of the benefit by going to mid grade, instead of full blown premium. Which sort of makes sense being as Toyota is recommending

89 octane, which is pretty close to the mid grade octane. I forgot what mid grade is usually rated at these days.. But it's at least two over regular.

Knock sensors detect knock long before you hear it. You will never know that the knock sensor has kicked in, until it fails. Ignition timing and valve timing are different things. Variable Valve timing is completely indepent of ignition timing that happens because the engine has a knock sensor.

That was the set up, you snipped the meat and potatoes.

Sure, but I still think it's adjusting the valve timing differently for premium, vs regular. How else would I explain the difference in the idle? It's not under load, so knocking wouldn't be an issue. The engine feels like the valve timing changes a bit with higher octane.

That was a test for a car that calls for premium. Mine does not call for premium. It just calls for 89 octane, which is a good bit lower than premium.

I will be happy to conduct a blind experiment with you, and show you how you're wrong.

But you proved it yourself when you defined the higher octane gas as "the good gas". It's not "the good gas" at all. It's not better than a lower octane gas. It simply has a higher octane rating, that's all.

But you think it is "the good gas," so you've fooled yourself into thinking "the car runs better" and "idles smoother". To say anything else would deny your stand that it's "the good gas," so of course you say what supports your thought that it's "the good gas".

Shell is the good gas compared to grocery store gas (or any other non-Top Tier gas), but octane rating has absolutely nothing to do with that.

No, it doesn't.

And "being as you see a difference" is meaningless, because you're seeing ghosts that result from your putting in gas that you erroneously think is "better".

You think that...why? Simply because you think that?

You know, there's this big thing called the internet. Without leaving your easy chair you can learn all about these things.

But you don't, because that would disturb your little world.

It's quite scary that people like you, who don't care about facts and care only about what you feel, can vote and serve jury duty.

Knock sensors set the ignition timing. Valve timing happens due to variables such as load and throttle position. At idle, you would not feel any difference in anything. as a result of premium vs. regular gasoline. Anything you think you feel is only in your head.

It's not a "good bit" lower, it is slightly lower. The same calculations hold true, but the margin would be different. Assuming $0.10 difference in the price per grade, when regular costs $3.50, mid-grade would be $3.60 and premium would be $3.70.

You still calculate the cost per mile the same way, if regular gives you 20 and mid-grade gives you 22, then 3.60 / 22 = 0.163, which is 0.012 per mile cheaper to use mid-grade than to use regular.

Just because the cost of filling the tank is less does not mean it costs less to operate the car. YOU HAVE TO DO THE MATH to know what is cheaper. There is more to the cost of operation than how much it costs to buy gas, you have to know how much it costs to USE gas.

If regular costs 3.50 and gives you 20 mpg, and if mid-grade costs 3.60, then all you need in mpg is 20.6 to break even, if you get 21 or 22, then you are ahead of the game, your cost per mile is lower on the more expensive fuel. Period.