Use Cheaper Gas?

[peter hausberg]

I'm new here, so I expect that this has been covered before. But....

I have a 2000 GS 300 and live in Southern California. Manual specifies 91 octane gas. Will running the car 0n 87 or 89 octane hurt the car?

Thanks for any help you can give.

[LexKid630]

The first few weeks my wife had her gs430 (which requires premium) she had put the medium grade 91 octane. There wasn't any noticable change for those few weeks though i would think that there would in the future. going to premium from 87 wouldn't have an effect in case you were thinking of that too.

[lexus ls430]

you could use any fuel on it but i would recommen 93 octane

[TurboGS300]

If the manual specifies 91 you better use 91 or higher. <_<

6.14) Does low octane fuel increase engine wear?

Not if you are meeting the octane requirement of the engine. If you are not meeting the octane requirement, the engine will rapidly suffer major damage due to knock. You must not use fuels that produce sustained audible knock, as engine damage will occur. If the octane is just sufficient, the engine management system will move settings to a less optimal position, and the only major penalty will be increased costs due to poor fuel economy. Whenever possible, engines should be operated at the optimum position for long-term reliability. Engine wear is mainly related to design, manufacturing, maintenance and lubrication factors. Once the octane and run-on requirements of the engine are satisfied, increased octane will have no beneficial effect on the engine. Run-on is the tendency of an engine to continue running after the ignition has been switched off, and is discussed in more detail in Section 8.2. The quality of gasoline, and the additive package used, would be more likely to affect the rate of engine wear, rather than the octane ratin B)

[peter hausberg]

Thanks for the replys.

I should have mentioned that 91 octane is the highest octane we can get in my part of SoCal. I was hoping I could save a few bucks by going to a lower octane.

[TurboGS300]

Thanks for the replys.

I should have mentioned that 91 octane is the highest octane we can get in my part of SoCal. I was hoping I could save a few bucks by going to a lower octane.

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Same here in AZ, however, I spend $30 to $40 everytime filling the tank. It's not worth taking the risk of damage or poor performance to save 10 cents a gallon. B)

[SKperformance]

If you want to be cheap in buying gas then it will cost you when you have to replace burnt out o2 sensors like the others who run cheap gas.

It runs hotter and the o2 sensor work on heat but too much and they wear out faster.

Just because an engine can retime itself to adjust to the lower octane with little notice to the drive does not mean it is doing any good.

[SRK]

O2 sensors will not be affected by the octane of the gasoline. All octanes are made to the same standards for purity and quality. The octane is determined chemically.

The ONLY time a higher octane fuel will be important is at or near full throttle. At engine loads less than that the lower octane fuels behave exactly the same, and the engine will not notice the difference. When the engine does, it will adjust within milliseconds, and no damage will occur.

How many times do we have to beat this subject to a pulp? And every time we do somebody has to get personal about it, and we don't need that on such a great board.

[TurboGS300]

Using a lower-octane fuel than recommended will lower MPG

Jim of Centerville asks if he can use regular-grade gasoline in his 2004 Chevrolet Impala SS equipped with the supercharged 3800 V-6 engine without causing any harm. He states that he likes to save money and the 20 cents a gallon difference between regular and premium makes a difference in the cost of a tank of gas.

The correct answer is that you should use the grade of fuel recommended by the vehicle manufacturer, which in this case is premium because the engine is supercharged. Most vehicles built since the early 1990s use a knock sensor to detect if engine-damaging spark knock occurs, which can happen if regular or midgrade (plus) gasoline is being used. The knock sensor signal is sent to the vehicle computer, which retards the spark advance until the knocking stops. This action by the computer will reduce the performance and fuel economy. Will this be noticed? Often, the difference in performance is not noticed, but often the fuel economy is reduced. Will it harm the engine? I doubt it. If you notice a drop in fuel economy, return to using the recommended grade.

[SKperformance]

SRK i am not suggesting that lower ocatane gas runs hotter i am telling you it is a fact.

I would have loved to hear you actual reasoning rather than an opinion.

Lower octane = easier to ignite

more fuel burnt = hotter combustion temperatures

That is why forced inductino engines need a higher octane gas to promote cooler temps by having more unburnt "cool" fuel running through the system and the turbo fins especially.

Now if an o2 sensor reacts to heat = resistance over heating it will cause it to fail sooner , just ask all the other people who save enough money by using lower octane gas to pay for the labour of the o2 but not the actual part.

[bartkat]

O2 sensors will not be affected by the octane of the gasoline.  All octanes are made to the same standards for purity and quality.  The octane is determined chemically. 

The ONLY time a higher octane fuel will be important is at or near full throttle.  At engine loads less than that the lower octane fuels behave exactly the same, and the engine will not notice the difference.  When the engine does, it will adjust within milliseconds, and no damage will occur.

How many times do we have to beat this subject to a pulp?  And every time we do somebody has to get personal about it, and we don't need that on such a great board.

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This information is incorrect and incomplete. Nothing personal.

[ford212.809]

Bartkat & SK,

Is there a websight or link somewhere that will backup your replys to SRK?

Nothing Personal... ;)

[TurboGS300]

Bartkat & SK,

Is there a websight or link somewhere that will backup your replys to SRK? 

Nothing Personal... ;)

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http://www.faqs.org/faqs/autos/gasoline-fa.../section-1.html

http://auto.howstuffworks.com/question90.htm

[SKperformance]

Well thank you for the backing up the basic priniciples.

I don;t take anything personal , don't worry.

I am here to learn and return it.

[OLY]

Bartkat & SK,

Is there a websight or link somewhere that will backup your replys to SRK? 

Nothing Personal... ;)

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http://www.faqs.org/faqs/autos/gasoline-fa.../section-1.html

http://auto.howstuffworks.com/question90.htm

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You know..., you are both right, to an extent. Just way to many variables. But to sum it up, just do what the manufacture recommends!! If its gas, oil change intervals, transmission fluid, coolant changes, etc. Why take the risk. You know the ol saying, "pay me now or pay me later" Usually later is more expensive.

[SRK]

Let's see, an O2 sensor reacts to......wait for it.......Oxygen! Well how about that. And to do so it must be at the correct temperature, which means in modern cars that it is electrically heated to maintain that temperature, something past 700 degrees F. Combustion temperatures are far higher, but drop quickly in the exhaust system, so much so that at idle, without electic heaters, most O2's will put the ECU back into open loop, which means the engine would fail emissions. Hence heated O2's. Gasoline octane does not affect them.

As I predicted, this thread is getting personal, assurances to the contrary notwithstanding. That's my opinion. Everything else I have written is fact.

I use 92 octane in both of my Lexi. I have used 89 when nothing better was available. I didn't worry about it for a second. I use full throttle frequently, and want everything that engine can deliver. And gas here is nearly $4.50 a gallon.

If you wish to read good information about all this stuff, then go to Bosch (the company that invented the O2 sensor in collaboration with Volvo), Denso, Delco, or other fuel system manufacturers, rather than a few rambling, poorly written, and misleading grade school level "articles" of questionable authority.

Begin the personal attacks gentleman, I can take it.

[TurboGS300]

I don't see anyone here starting a personal attack, nor do any of those "grade school" articles even talk about O2 sensors and low octane. They were all to show that there are problems with using lower octane fuel than is reccommended by the manufacturer! Namely lower fuel economy and reduced engine performance. However you answered the question of "should I use lower octane than reccommended"? in your statement that you use 92 octane in both your Lexi <_<

[SKperformance]

Oxygen which is degraded faster by higher heat levels.

Nothing personal but do some more digging before coming up with a wise crack answer.

Know it alls usually really know nothing........

[SRK]

Oxygen which is degraded faster by higher heat levels.

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What is the extent of your knowledge of chemistry? And what do you know about the operation of an O2 sensor?

Oxygen is not "degraded" by "heat levels". It is consumed during the combustion process, or combined with other elements to form other compounds, like CO, CO2, and oxides of nitrogen. The level of O2 not consumed by combustion or compounding with other atoms, is that which is detected by the O2 sensor, which uses ambient air as a reference. A voltage is generated in the sensor when there is a difference in the oxygen content of the exhaust gas compared to ambient air. More exhaust gas oxygen, less voltage and conversely less exhaust gas oxygen, more voltage. It does not detect fuel, it detects oxygen. If the engine burns 87 octane or 94 octane at the stoichiometric ratio, the O2 sensor will read the same - about 500 millivolts. It cannot detect the octane, or the temperature of combustion. Universal fit O2 sensors are sold all day long to fit cars of varying compression ratios, and none of them are designated for use depending on octane. It simply isn't a consideration. More cars by far operate on regular fuel than premium, and since 1987 all of them have O2 sensors. The service life of an O2 sensor may be degraded by many things, but octane isn't one of them.

I have done my best to explain this and the only response from you is that I am "wise cracking" and that I know nothing.

[ford212.809]

<_< I am not a gambling man, however, judging from SRK's profile/website and

his experience/AGE, I would be willing to say he KNOWS what he is talking

about. :D

[SKperformance]

I don't gamble much either , the last answer is better but still just states basic principles not any conclusive research in favour of his beleif.

I ment to say "Oxygen sensor " not just oxygen.

It is very consistant with everyone who builds race engine works as a technition or anything in the feild of engines lower octane runs hotter .

Heat breaks down anything faster . It doesn't matter if it is made for high temps as running it higher just reduces its life.

It is easy to prove that anyone with a turbo or superchargers knows that as well. My exhuast temp gauge proves the 200 degree difference.

I am willing to be wrong or misinformed with anything , their is nothign bad about being wrong. I am adament in this because i know its effects.

[jgr7]

Some more good info on octane, see my posts #20-21.

http://us.lexusownersclub.com/forums/index...hl=octane&st=15

Jeff

[SRK]

Some more good info on octane, see my posts #20-21.

Jeff

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A very well written response on the subject of octane.