WARNING: do not put anything lower than 91 octane gas (US specs) in your 3IS and also the 2IS as well.
Both engines (250 & 350) have been designed to operate on that specific gas and the ECU will not adapt to lower octane like other engines that accept different octane.
If you have no option when filling up to put lower octane, only fill up about 1/4 of the tank and find another gas station and fill up the rest with 91.
Many people think this is all BS and that they can put anything they like. WRONG. The timing on the engine has been designed for the slower burning the 91 octane gas has. It allows to burn it all and use maximum energy from it.
Using lower octane will result on waste of energy, carbon build up on the valves, and knocking on the lifters (that is a VERY BAD THING). You will lose power which will make you hit the gas pedal harder resulting on extra $$$ out of your pocket (besides having to fix the engine on the long run).
Use ONLY 91 octane gas.
__________________ 2014 Lexus IS350 F RWD - Matador Red Mica
2013 Lexus CT200h - Obsidian
1990 Nissan 300ZX 2+2 Twin Turbo 500 RWHP - "The Silver Bullet"
Use 91 Octane. The higest grade possible is needed due to our engines direct injection and high engine compression ratio. Now unlike older vehicles, you can put a lower grade octane into these vehicles because the ecu is smart enough to adjust for knocking and pinging. So once in a jam or emergency is fine, but prolonged use will affect both engine perfomance and fuel economy.
For those of you putting in anything less than 91... I'm just going to flat out say drink less Starbucks
But seriously lease or not.. Use the correct premium gas.
It comes out to $3 a tank between 87 & 91, if the difference is .20 cents.
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^^^when I travel to the US, I put the higher octane gas because it's so cheap. In Canada it's 12-15 cents more per liter. On a 60 L (~16 US Gallons) fill-up, the dollars become more apparent @ 8 to 9$ more per tank.
I've filled 91 three times, once 94, and my current tank at 89. I noticed a slight improvement in power and response going to 94, and a bigger difference dropping down in power going to 89. The car today feels less responsive as though I have 5 passengers in the car.
Moving forward, it will be 91 most fill-ups and when I have the bigger urge for more power, 94. Too bad 94 costs 20 cents more per liter!!! I wonder if those octane boosters added to my 89 tank will work to bring it up a few points...
The manufacturer has clearly stated to use PREMIUM GAS. 91 or higher for those here in the US. They (Toyota / Lexus) do not have any vested interest to make us buy more expensive gas. It's purely based upon the engineered needs of the engine design.
(Getting on soap box and not directing this at the OP)
We all just bought $35k+ cars so don't "nickel and dime" your gas at the risk of ruining the main component of your ride and as one poster noted, if you want to save a couple of bucks on something.. cut down on the Starbucks.