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i have a 1997 5-speed sc300, i dont know what type of octane to use?

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Would guess a Super unleaded grade. Every Lexus I have owned runs premium fuel. Call your local Lexus Dealer for details. They will be happy to give you the details.

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From experience the older the model the higher the octane, with time and age the engine components gain wear and tear, slowing down performance and causing the car to run sluggish or not at it's best considering you keep up with your recommended service Sometimes people use lower grade gas to save a buck or two in the end you end you could end up with costly repairs from all that damage done from lower octane gas, the lower the octane the less the knock characteristic it has to protect it from premature detonation . Even with all the technology TOYOTA puts into there LEXUS Line there's still nothing better then a higher octane, for your vehicle,

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Best reference I know of for fuel requirement and choice: http://www.roadandtrack.com/new-cars/car-technology/news/a18008/premium-fuel-futures/

The author, Dennis Simaniatis, was Road & Track tech editor for years, and was previously with SAE (Society of Automotive Engineers). His expertise is well documented.

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Good article, includes helpful discussion of modern powerplants too.

Regarding which to chose? (per article, and as stated earlier in thread)

"follow automaker advice contained in your car's owners manual"

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Agree. Despite cynical comments from the public and various pundits, there is a reason why manufacturers make recommendations / specifications for fuel, lubricants, etc.

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Yes. I see them in line at Costco waiting to buy gas sometimes when I drive by.

Here in CA the uplift for premium is only 5% to 7%, a minor impact on operating costs for those driving cars where premium is recommended by the automaker.

But maybe OP doesn't have the owners manual that originally came with the 1997 SC. Maybe somebody can chime-in on fuel requirement per Lexus for that specific car.

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You will not hurt any modern engine designed to run on Premium fuel by running regular. The computer will make sure that doesn't happen. Of course this also means your engine is not running at optimal performance since adjustment are made to protect the engine from any pre-ignition. My feelings are IF you buy a Lexus, you can probably afford the Premium as well.

I do know that the specs for my 2004 ES330 calls for 91 octane.

Now here is something many of you Premium fuel users may not have considered. WHERE you buy your fuel. If you buy fuel from a station that uses one pump handle for all grades, the first gallon you put in is regular since that is about what the lines hold. If possible find a station that has individual pumps for each grade, OR wait until a Corvette or something fills up in front of you.

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One gallon in hose? I guess the stations here don't have the same 6" diameter fire hoses, lol.

Yes using recommended fuel is minor difference in operating cost.

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The hoses are really long so people can stretch them around to the wrong side. Consider that when you select premium and the car before bought regular, by the time the premium fuel purged all the regular, about a gallon.

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I'll take the "1 gallon" remaining in small diameter hose as a unmeasured and unsubstantiated guess at best and not worry about it. Recent estimate per Shell puts it at 1/2 litre or about 1/8 gallon. Motorcyclists riding old high compression bikes with very small 2 gallon tanks are aware of impact of remaining fuel though as they should be. For regular Lexus drivers like us, not significant.

My preference is to use nearly 100% Chevron because of the detergent/additives, even if other brands claim top tier the (minimal) additive amounts and qualities are different. I learned from a (fellow Mazda-owner) engineer that worked at a major gasoline distribution center.

Also running regular in a engine designed to run on premium will negatively impact performance and fuel efficiency (reducing net cost savings), not good for long term use.

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While in upstate New York last week I see Sunoco sells 91 NON-alcohol Premium. Engines love it.

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