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2011 rx350 octane

I have a 2011 rx350 lexus that calls for premium fuel. In 2012 they modified the same engine to run on regular fuel. Was that a minor tweeking,if so can a mechanic do it. If not,is mid range ok to use?
What would be the ideal octane on a trip?

Does the manual say premium is recommended or required? If it’s required, then it’s required. Otherwise, you can use lower grade gas, but you will suffer a performance hit.

I don’t know what they did in 2012 to make it run on regular gas, but whatever it was would probably cost you more to modify, if that were even possible, than you would save in gas bills.


An extra 40 cents per gallon seems like a lot of money, but it works out to only an extra $200 for 10,000 miles at 20 MPG. The mileage is the average for your RX from the EPA web site, This is if there is no change in mileage for using regular instead of premium. Your gas mileage will likely suffer and that will decrease the $200 savings. It seems to me that having optimum performance for your RX350 is worth the $200 per 10,000 miles, even if you can use regular. It’s your choice, though, not mine.

Like @shadowfax said, it’s all in the manual: “recommended” or “required”. I bet it says “recommended”. That’s what my ES300 said, I used regular after finding no difference in power or economy. Your 3.5 L V6 is basically identical to that used in the Highlander, which I think uses regular.

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Here is what your owner’s manual says:

Premium unleaded gasoline with an octane rating of 91 (Research Octane Number 96) or higher required for optimum engine performance. If 91 octane cannot be obtained, you may use unleaded gasoline with an octane rating as low as 87 (Research Octane Number 91). Use of unleaded gasoline with an octane rating lower than 91 may result in engine knocking. Persistent knocking can lead to engine damage and should be corrected by refueling with higher octane unleaded gasoline.

If this were my car, I’d use premium, especially when you consider that the engine might retard the timing and reduce your fuel economy when you use regular.


Here’s my issue: the engine in the Highlander is the same, including compression ratio. It’s rated at 270hp vs. 275hp for the RX350, which looks like optimizing for premium gas. If the only real cost is the loss of 5 hp (and maybe some fuel economy) I’m willing to try it out and see if there is any difference. Of course, if any knocking occurs I’d be back on premium immediately. But $0.50/gallon (around here) is significant, to me.

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You use a lower octane at your own risk.

Nobody other than the engineering team that designed the engine knows exactly why one version requires premium and the other only requires regular. Engines are very complex design projects, full of eccentricities, and if it were my engine I’d be highly reluctant to make any assumptions.

Your money. Your call. I wouldn’t do it.


As far as I can tell, it’s the result of different ECU mapping. Tuning the ECU is not something that typical independent shop would do. It’s more in the realm of dedicated performance shops. The dealer can do it as well, but they might not be willing to due to the liability issue. I guess if you really wanted to, you have the vehicle dyno tuned to run on regular, but that would cost a couple hundred dollars, probably more that you’d ever save over the life of the car given the price difference between regular and premium

91 octane is the stated minimum. For this vehicle, premium is a requirement, not a recommendation.

91 octane or better.

My car recommends premium grade, but I have used mid grade without any issues for over 50K miles.

I have had no knocking.

I found no mileage increase when I used premium grade.

Gas stations ream customers who use other than reg gas.

No they don’t because no one forces them to buy premium and their cost is higher. Andrew, stop making blanket statements.


One reason premium gas is going up in price is all the new cars that recommend/require premium. Think about all those high-output turbo motors. There’s concern in the industry about this:

My info is from retailers and refinery workers.

You have to pick on someone else.

Some high output engines use regular fuel. The 3.6L direct injection engine used by Cadillac has 335 HP with regular. Chevrolet and Buick the same engine with lower horsepower levels and also use regular fuel. Cadillac has a twin turbocharged 3L engine that does require premium fuel, but that’s reasonable for its very high output. Maybe others will do the same. Mazda does.

thanks for the comment

thanks,makes sense