premium octane fuel? 87 vs 91?
Thread Starter
Lead Lap
Joined: Feb 2008
Posts: 546
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From: california
premium octane fuel? 87 vs 91?
I have a question lexus recomends premium unleaded fuel of 91octane or greater, i was looking online for a descent family car rx 300, then when i came to ask the owner on who's rx300 i was interested i asked him a question, i asked him does he always use premium unleaded of 91 octane or greater, he said he mostly used 87 octane fuel with no problems.... so now i backed out and have a big question in my head if lexus recomends 91 premium fuel what will happen if you used 87 octane fuel instead? can you harm anything on your vehicle? can any expert in this forum please advise on what could go wrong or bad and etc if you went to 87 fuel octane? i know putting 91 premium fuel makes car smoother and more responsive and lessknocks and pings but anything other then that that can cause maintaince issues and etc? thanks
They recommend premium for 2 reasons:
Firstly to allow the engine to operate at it's optimum timing - 87 octane willlikely cause the knock detector to kick in a retard the timing loosing some performance and some economy (yes).
Secondly, premium gas contains (more) detergent than regular to keep everyhting a little cleaner.
It probably hasn't done the car any damage but you actually don't gain much by cheaping out!
Firstly to allow the engine to operate at it's optimum timing - 87 octane willlikely cause the knock detector to kick in a retard the timing loosing some performance and some economy (yes).
Secondly, premium gas contains (more) detergent than regular to keep everyhting a little cleaner.
It probably hasn't done the car any damage but you actually don't gain much by cheaping out!
Driver
Joined: Mar 2002
Posts: 1,800
Likes: 13
From: Maryland
I thought the owners manual said to use 87 octane gasoline in the RX300. That's what I've been using. What am I missing?
My mother's ES300 of the same year (2002) recommends 91 octane gasoline. The car brothers on PBS radio (click and clack the tappet brothers) have said that using a lower octane than reecommended in the onwers manual will cause the engine to run hotter than normal. As the price of gasoline has increased and the spread between 87 and 91 octane has remained constant, the percentage increase in cost has gone down.
My mother's ES300 of the same year (2002) recommends 91 octane gasoline. The car brothers on PBS radio (click and clack the tappet brothers) have said that using a lower octane than reecommended in the onwers manual will cause the engine to run hotter than normal. As the price of gasoline has increased and the spread between 87 and 91 octane has remained constant, the percentage increase in cost has gone down.
Lexus Champion
Joined: Jan 2003
Posts: 2,754
Likes: 6
From: Colorado
The RX300 manual recommends 87, though it also says higher octane can give better performance.
I use mid-grade (87 in Colorado) which gives me 10% better gas mileage vs. regular 85. The premium 91 does not give me better gas mileage over mid-grade.
Not sure about the performance. All 3 grades feel the same to me in Colorado mountains.
I use mid-grade (87 in Colorado) which gives me 10% better gas mileage vs. regular 85. The premium 91 does not give me better gas mileage over mid-grade.
Not sure about the performance. All 3 grades feel the same to me in Colorado mountains.
Thread Starter
Lead Lap
Joined: Feb 2008
Posts: 546
Likes: 0
From: california
so thats what the owners manuel recomended is 87 gas? kool because gas price for premium is 3.99 dollars a gallon i figure i could go use the rest of the money to have a bite to eat at mcdonalds or something lol....
They recommend premium for 2 reasons:
Firstly to allow the engine to operate at it's optimum timing - 87 octane willlikely cause the knock detector to kick in a retard the timing loosing some performance and some economy (yes).
Secondly, premium gas contains (more) detergent than regular to keep everyhting a little cleaner.
It probably hasn't done the car any damage but you actually don't gain much by cheaping out!
Firstly to allow the engine to operate at it's optimum timing - 87 octane willlikely cause the knock detector to kick in a retard the timing loosing some performance and some economy (yes).
Secondly, premium gas contains (more) detergent than regular to keep everyhting a little cleaner.
It probably hasn't done the car any damage but you actually don't gain much by cheaping out!
Just buy one latte less and you've offset the cost of the price differences.
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Mine has seen 87 octane all its life. 110k miles.
What are knocks, pings, unsmoothness? Never experienced any of those.
Not like we have a high performance engine in our cars.
What are knocks, pings, unsmoothness? Never experienced any of those.
Not like we have a high performance engine in our cars.
Last edited by gsrthomas; Feb 22, 2008 at 10:35 AM.
Lexus Champion
Joined: Aug 2007
Posts: 4,507
Likes: 38
From: Bethlehem Twsp. Pennsylvania
I believe I can add to this thread,I sent lexmex a private message on this topic of reg.vs prem. gasoline.Here is what I discovered,first tank of reg. it ran real good,second tank of reg.well,it must have figured out what was going on.Lost performance BIG TIME!,felt like I was driving a grand torino with a 200 cid six cylinder under the hood,(yes that bad)switched back to premium(same gas station btw)and almost an instant gain in performance,and throttle response.Gas milage didnt seem to change much in my trial period.As for the engine being high performance?I did some research on that,and found lexus tweaked out this camry engine vie. timing and computer related tuning.that is why a 2001 camry and a 2001 rx are not rated the same horse power.rx has more.As far as running hoter on reg.,that could happen,due to ign. timing being @ a retard status(engines do run hoter when timing is retard) so,food for thought.Thats what I personaly have discovered.
Lexus Champion
Joined: Feb 2007
Posts: 2,489
Likes: 4
From: Lou-Evil KY
