Premium fuel in the GX470 necessary?

trust me you have to use premium and i mean mobile,shell,amoco,thats it "James P. Clark" wrote in message news:zywzb.8695$ snipped-for-privacy@news1.news.adelphia.net... I've got a GX470 on order and should be picking it up next week. I know that Lexus recommends premium gas be used, but I'm wondering if there would be ill effects in using regular octane gas instead?

The general rule of thumb on recent cars is that you can use regular, but you'll reduce performance about as much as you'll save in gas. So if you don't want/need/use all the performance of your GX, go for it. But it always seems like weird economy to spend big money on a high-performance vehicle to feed it cheap gas that turns it into a cheaper, lower-performance vehicle.

- Mark

If you like your car's engine, use premium, it's worth it. I doubt the few dollars saved relative to the cost is significant... or... penny wise, pound foolish.

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i switched to regular in my '91 LS400 and I haven't noticed anything different at all. No knocking or pinging at all.

that Lexus recommends premium gas be used, but I'm >wondering if there would be ill effects in using regular octane gas instead?

You do not need to use premium. The engine down-tunes itself for lower octance gas, with no ill-effects.

Dan

Ignoring his agents wishes,"John" flung open the hotel room door and announced to the gathering crowd:

you will *not* damage your engine by going with a lower octane fuel. You *can* damage your engine by going with too *high* of an octane fuel for an engine that's not designed for it. Higher octane is to prevent predetonation in a higher compression engine. If you don't have a high compression engine or if you're not getting any knocking, you're not going to lose losing power and your not going to hurt your engine.

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-Unknown

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I've got a GX470 on order and should be picking it up next week. I know that Lexus recommends premium gas be used, but I'm wondering if there would be ill effects in using regular octane gas instead?

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Ignoring his agents wishes,"Carl" flung open the hotel room door and announced to the gathering crowd:

experienced nothing but lower gas bills. No performance problems, no engine damage, no nothing, just plain old lower costs.

Lexus recommends premium gas be used, but I'm wondering if there would be ill effects in using regular octane gas instead?

"Are you tempted to buy a high octane gasoline for your car because you want to improve its performance? If so, take note: the recommended gasoline for most cars is regular octane. In fact, in most cases, using a higher octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage or run cleaner. Your best bet: listen to your owner's manual."

.....however...

"What's the right octane level for your car? Check your owner's manual to determine the right octane level for your car. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock"

....but....

"Should you ever switch to a higher octane gasoline? A few car engines may knock or ping - even if you use the recommended octane. If this happens, try switching to the next highest octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking."

from: "The Low-Down on High Octane Gasoline"

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Please explain how using too high of an octane fuel can damage an engine. Although it may not make sense from an economic viewpoint, the only difference between low octane and higher octane is that higher octane burns slower (which is why it pings and knocks less). Some say higher octane also has higher detergent levels, but I have never been able to verify this.

For what it is worth, in my GS 300, it recommends premium for best performance but does not rule out lower octane fuels. I have tried regular, mid-grade and premium and can not tell any difference in performance. So, I compromise and use mid-grade. Most modern engines have the ability to sense knock/ping and will automatically retard the ignition timing to compensate for the lower octane fuel, with maybe a slight degree of reduced performance. Steve

Gas doesn't burn "slower" or "faster". The octane rating is relative to the temperature at which the gas burns. Higher octane gas combusts at a higher temperature than lower octane gas. Compression heats the fuel/air mixture, and if the octane level is too low for the engine, the fuel/air will combust from the compression heat before the spark plug ignites it. That causes knocking.

Well, this is a chicken/egg argument. No, you're not going to be able to detect knocking on regular, but that's because the engine has detected it long before you could, and has reduced engine preformance to elminate it.

So "not getting any knocking" tells you basically nothing about what your engine is doing or what octane appetite it has.

- Mark

You're right, it can't. This is an old wive's tale. Using a high-octane fuel in an engine designed for lower-octane does nothing except waste money.

- Mark

Except a loss in performance. You may not detect it, but the dyno doesn't lie - you run most premium engines on regular and peak horsepower drops 10% or so.

- Mark

This document says nothing about modern engines with knock-sensors. It is completely out of date.

- Mark

From some of the reports that I saw, it's more like 2% performance decrease... I will try to find the article again.

C&D is the only definitive test I've seen.

- Mark

Agreed. But the flame front actually takes longer to advance (milliseconds) so there is a slower burn. At least that is how it was explained to me by my Technology instructor in college. Also, think about diesel fuel for a moment. Diesel fuel is a light fuel oil and has a lower octane that gasoline (actually diesel fuel is measured in cetane, if I recall correctly) It would take a much higher temp to cause diesel fuel to ignite than it would gasoline, yet by your reasoning the opposite should occur.

I've got a GX470 on order and should be picking it up next week. I know that Lexus recommends premium gas be used, but I'm wondering if there would be ill effects in using regular octane gas instead?

-- Please remove all UPPERCASE letters in the reply email address!

I've got a GX470 on order and should be picking it up next week. I know that Lexus recommends premium gas be used, but I'm wondering if there would be ill effects in using regular octane gas instead?

-- Please remove all UPPERCASE letters in the reply email address!