Hello Everyone,
I am new to this forum. Just purchased a 2023 IS350 RWD and had a question about fuel type. The salesman I dealt with recommended 89 octane or higher. Can anyone give any insight to using 89....is it ok? Thanks in advance.

 

91 or higher. That is what the owner's manual says. Salespeople are known to improvise if they think it'll help them make a sale, going as far as to say break-in periods aren't required, etc.

The car CAN run on 89, but it will potentially experience damage and will have less power output and fuel economy. Personally, I never use anything less than 91 and never will unless there's none available.

 

I have only 400 miles but have been using 89 and 93. 91 hard to find . I use a top tier and alternate 1/2 tanks between 93 and 89(so far). The car will just pull timing if the octane is low. It s not like the old days where a car would just knock constantly. I m sure the dealer just filled it with 87 anyway, LOL. They had one pump at the dealer. I wouldn't risk running 87 unless it was an emergency.

 

Thanks, i'll stick with 93 to be on the safe side.

 

Just to add to the conversation, many countries have poor fuel quality and Lexus knows that. They certainly leave a margin of error factor. That s what an aftermarket tune does, it s runs the ECU closer to that margin for performance and then you certainly have to use the highest octane. I had a WRX (tuned) with the plugin handheld to actually see if the engine is running and reducing timing or the opposite (knocking). I ran a v8 Mercedes for 50K on regular when it called for premium and my nephew still has the car over 100K. So I m not overly concerned but like I said will mix 89 and 93. Not exact science , LOL.

 

I know what you mean, I've had 3 NX F Sports and 2 IS250 F Sports which i used 89 from day 1 with no issue. However, this is my first 350 so I was curious what everyone else was doing. Side note....it's crazy to me that the IS does not come with auto folding side view mirrors....drives me nuts.

 

I stick with the manufacturer's recommendation at a minimum.

US gasoline and service stations leave a lot to be desired so I like to splurge on the safe side even for my cars that don't require premium fuel... especially when it's 105 degrees outside here in Houston.

 

Do what the factory recommends. They know best through decades of testing beyond anything we can figure.

 

Can i put 89 octane in my Lexus IS or will it cause damage, I asked lexus and they said if you have to you can get away with it just dont make it a habit. Ive only ever filled up with 91.

 

87 octane won’t hurt it but the power and fuel economy will suffer significantly enough to take away the cost savings. The car adjusts the timing so that there won’t be predetonation. This has been the case for decades now.

Cliffs: using 87 or 89 won’t hurt the car but it will run worse and you won’t save any money since you’ll use more gas. So use 91.

 

If you do the math at the pump you aren’t saving much money by using a lower octane. Multiply your gas prices by 16 gallons and you’ll see only a few dollars difference. Never mind how poor your engine will run and how much money you’ll lose on inefficient fuel use. If you live in an area where you can’t get the right gas, do some more research before buying a car.

 

89 is a half-measure. You didn't buy a half-Lexus.

The owner's manual clearly states that 91 is REQUIRED. They go on to say that the engine may sustain damage if anything lower than 91 is used and to fill up with 91 or higher as soon as possible.