Here we go again - Octane level

On Sat, 15 Apr 2006 20:33:25 GMT, "billyzoom" graced this newsgroup with:

It's always best to use the recommended octane level for the car. You can usually get away with one or two octane lower with no problems. Your knock sensor will compensate.

Of course it best to use recommended brand of gas. What I am looking for is someone who has had their vehicle for an extended period of time, and has real world experience. I guess it really doesnt matter at the rate I am racking up the miles, about 30k per year, I will buy probably buy a '06 or '07 GS300 in a couple of years.

I use regular in my rx 330 with no ill effects, I always used reg in my cars even when premium is recommended and never had anything bad happen. you might see a slight lessening of gas milage, 1-2 mpg lower and a very slight hit when accelerating, but unless you need to be first off the line everytime it shouldn't make a difference YMMV

I've been using 87 octane in my 94 ES for as long as I've had it, about

28 months now. I got it with 124K on the clock it's now at 162K.

I have gotten a steady ~20 in town and ~25 on the highway (as high as 27 occasionally). No ill effects.

And after all, the owner's manual *does* say that you can use lower octane fuel without harming the engine.

So what does your owner's manual say?

OK, which REALLY leads to the question: why is it "always best to use the recommended octane level for the car"?

And what if the recommendation from the owner's manual is like what you said: "use 93 octane, but nothing bad will happen if you don't"?

On Sat, 15 Apr 2006 20:45:13 GMT, "billyzoom" graced this newsgroup with:

Our 00 ES300 routinely runs on 87, although when we fill up at Costco, the price of premium is the same price as regular elsewhere so we fill up with premium there.

We now have 65k on the odo.

On my 02 LS430, I pretty much stick with premium although I've used regular a few times when premium was out at the local station. It has 45k on the odo.

As Elmo has already stated, the only real difference has been a slight loss of power and a 1-2mpg drop.

It's almost always safer to drop in octane level from the recommended octane but it's not a good idea to use premium fuel in an engine that doesn't require it. It can cause an excessive buildup of carbon on the piston heads and valves.

Is that real world enough?

On Sat, 15 Apr 2006 17:39:06 -0400, "Elmo P. Shagnasty" graced this newsgroup with:

because performance and mpg usually suffer.

then use 93 octane or lower. The lower the octane level, the more pure the fuel and the faster the detonation. The timing will automatically be retarded to compensate for knock but in retarding the time, performance and mpg will suffer.

MPG is up in the air; performance, so what? For everyday city driving, for the average Lexus driver, will any of them notice any difference?

On Sat, 15 Apr 2006 18:55:06 -0400, "Elmo P. Shagnasty" graced this newsgroup with:

nope probably not and the difference would probably only be noticeable on a dyno.

What's the engine's compression ratio? If > 10.0 : 1 the need for higher octane fuel grows.

High octane gas ignites at a higher temperature than lower octane gas. That's the difference; and its used in higher compression motors.

So? If the fuel ignites too soon - before the piston reaches the top of its travel - the motor is working against itself and one hears the "pinging" of preignition - ignition from sources like carbon etc., other than the spark plug which fires at the correct time.

Modern engines have knock sensors to detect preignition and when they do the ignition is retarded a bit to depower the motor and so reduce the preignition. 89 fuel may seem OK but it has some performance penalty, particularly in hot weather when preignition is more prevalent with all fuels - because everything is hotter!

The more moderately you drive the car the easier it will be to "get away with" using lower octane fuels, but give it a break and use high octane in the hot months.

I used regular in my 1997 ES for 70K miles and it was fine.

Based on discussions here, I switch to using premium on my 2004 ES and it improves performance, particularly in light of the hesitating tranny, which doesn't bother me as much using premium.

If it's a 2 mpg difference, then premium would actually work out to be cheaper than regular. (And according to some folks here, better for your car). If premium results in a 1 mpg improvement, then premium turns out to cost about 3% more, which is about $40 or $50 more per

10,000 miles. Seems more than worth it to me for better performance and, according to some, better for your car.

I agree. It all depends on how much mpg improvement you REALLY get from premium.

Not sure what your dealer told you or what your manual says, but regular is what is recommended for the RX330. That's all I've every used in mine. ;-)

Something's wrong here, 16 MPG on a GS300, your foot must be all the way into it. We have a 98 GS 300 and have a few friends who have either GS 300 or 400 and none of them gets less than 20 MPG unless they are really pushing it. Our normal MPG is 21-24, town, 24-28 Highway trip 75-80 MPH. Many of us have tried regular & premium and have found that premium pays for it's self on the highway with it about a wash in town.

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none of them gets

town, 24-28 Highway

premium pays for it's

Just about what I have found with my 2006 GS300, 1997 Avalon, and 1998 Audi A6 -- the increase in mileage more than offsets the difference in price. If the car call for premium, buy it and save -- especially on the highway!

Try driving 50 miles one way in LA traffic 2 hour commute each way, then let me know what your milage is. I recently went to vegas and got about 23-24 miles per gallon average speed about 85-90mph.

And your point is... ?

That sitting and idling for two hours burns a lot of gas, hence screws your mileage.