The Eco light means your Variable Cylinder Management (VCM) is engaged and that you are using either 3 or 4 cylinders, and not all 6, thus saving fuel.
there is no ECO mode in the RX350, that is unique to the RX450h. The ECO light is the only thing that the RX350 has. Im not sure if you can turn that off. NOTE: ECO light does not change the driving habbits of the car like ECO mode. It looks at your own driving habbits and illuminates the light if you are driving frugally. It does not change the pedal resistance like ECO mode does on Posts: 2. Question: ES 350 MPG difference among Eco/Normal/Sport. Hi Everyone, Does anyone know the MPG difference among Eco, Normal and Sport mode. I would like to know how much gas savings I can make driving with Eco mode, and how much more gas spending driving with Sport mode instead of Normal mode. I would greatly appreciate if anyone can tell me what is the MPG for Eco mode and Sport mode. I believe this 21/31 MPG is based on Normal mode. I was thinking to buy a ES 300h but changed my mind to buy ES350 because I was able to discount a lot more. This is my first Lexus. Elliot is very correct. I actually calculated this; I first started with Eco mode and drove 300 miles and filled up, I got 24.46mpg, then I tested the Sport it came out to be 24.44mpg and the last one was normal and it came out to be very close to Eco mode. If you've shopped for a new car in the past year or two, you may have noticed a new feature that's creeping into all sorts of models: The eco button.. Manufacturers are installing the little, illuminated squares of plastic in everything from hybrids to sporty coupes, high-horsepower sedans to V8-powered SUVs.  Since you mentioned the ECO light I am assuming you have a V6 model. When the ECO light comes on it means that 3 of your cylinders have cut off and the car is only running on the other 3. It burns less gas that way, which gives you better gas mileage. I have an 06 Honda Odyessy and it does the samething. Great on long trips with cruise control. Best Answer: The Eco light means your Variable Cylinder Management (VCM) is engaged and that you are using either 3 or 4 cylinders, and not all 6, thus saving fuel. This link explains it very well http://automobiles.honda.com/accord-seda... . Lexus believes that we Lexus drivers can't chew gum and !Removed! at the same time. You use the DISP button on the steering wheel to toggle to the ECO light setting. Hold in the DISP button for several seconds and the indicator will change to either off or disabled, I forget. You can also turn it back on the same way.You keep punching the DISP switch on the right side of the steering wheel. 
http://www.clublexus.com/forums/rx-3rd-gen-2010-2015/440001-eco-light-and-eco-mode.html http://www.clublexus.com/forums/es-6th-gen-2013-present/676179-question-es-350-mpg-difference-among-eco-normal-sport.html http://www.autoblog.com/2011/01/28/car-eco-button/ https://answers.yahoo.com/question/index?qid=20080904091515AA75UfN http://us.lexusownersclub.com/forums/topic/62542-2010-es-350-eco-light/
what does ECO mean in a lexus