2015 Lexus NX - Premium vs regular

I purchased a Lexus NX200t. When I went to fuel it the fuel door has a message that says it requires premium fuel. The dealer said that the turbo requires it. I plan to keep this car forever but the extra $6.00 per fill up is killing me. What long term damage can be caused by using regular instead of premium?

You really want to save 6.00 and run the risk of an expensive Turbo repair . The people who built the vehicle put that note on there for a reason. At 2 fill ups a month that is only 144.00 a year . That would not even cover the diagnostic fee is you had a problem by not using the correct fuel.

Since you have a Turbo engine the correct oil and oil change period is also important.


Under certain conditions it is possible for a fault to be set in the PCM; P137800, Pre-ignition detected when using the wrong fuel and the vehicle will go into limp mode.

BTW these vehicles were more than $35,000 new.

If you think an extra $6 a fill up is expensive, wait til you see what a hole on a piston costs.

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Lexus offered another engine in the NX that year that did not require premium. Like many premium brands, that model you chose does use the expensive stuff (with absolutely zero benefit BTW).

Sounds like you bought the wrong vehicle for you. Turbo engines typically require premium. Not all do, but yours does.

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I have a 2009 Dodge with the 5.7L V8 that “recommends” plus or mid grade fuel. Note the difference in “recommends” vs. “required”.

Anyway, I’ve found it gets slightly better gas mileage with mid grade gas, but you pay more for it per gallon. I’ve done the math (I shuffle spreadsheets), and there’s really only about 1/2 cent difference in using plus vs regular, assuming your MPG do increase.

The point of all this is while it sounds like your car requires premium fuel… it may actually be getting better fuel economy with the premium. You may be paying less per gallon for regular, but get lower MPG. Try and look at the whole picture instead of just your cost per week per tank.

Good luck.

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Thanks, I needed a laugh this morning. You’re talking about the price of a cup of coffee.

If $6 a week is more than pocket change to you, you need to reconsider your transportation choices.

Your car requires premium, use it.


There are benefits to requiring premium fuel. The manufacturer can tune in more spark advance, more turbo boost and more static compression. This provides more power and greater efficiency. This improved efficiency gives higher mpg’s to the consumer and better CAFE for the manufacturer.

Per page 592 of your owner’s manual. The dealer is correct. This vehicle requires premium fuel. Note. Not recommended but required

If you’re sweating over $6 a fll up, then you chose the wrong vehicle. Lexi are higher end vehicles, higher end vehicles have higher end upkeep costs.

I’ve seen cars with forced induction that were run on regular (instead of the required premium) get holes in pistons from pre-detonation. Your warranty will be flat out denied if it’s discovered you were using regular fuel. Repair costs will be well into the thousands. It’s easier just to use the specified fuel in the first place.

In general, I agree with you MustangMan. Except that the 2-liter turbo in the Lexus NX has the lowest power and torque in its class. Lower than many equally-sized 2-liter turbos that are rated for premium (for example the Hyundai & Ford 2-liter turbos). Almost no automaker rates a mainstream vehicle for “Premium Required” only anymore. Some still recommend it. The reason is spelled out by the Poster. Here isan image of how Acura rates its new RDX with a 2-liter turbo (much more power and torque than the Lexus)

If there are any practical benefits to Premium in modern non-high-performance vehicles I have not seen it. Nor has Consumer Reports in its testing, nor AAA in its. The real reason automakers opt to rate their cars using premium is the slight fuel efficiency gains they can record. Which are then negated by the fuel’s higher cost to the consumer. Here is a good overview.

You bought a Lexus and you can’t afford 6 bucks a week?

You bought the wrong car.


You are missing the point. There is a difference between “required” and “recommended.” The NX 200t is “premium required.” It doesn’t matter if the Lexus makes more or less power than others in its class. It only matters whether Toyota (Lexus) designed the engine to require premium or not. Very clearly they did. Engines have varying degrees of sensitivity to detonation or pre-ignition and HP is not the defining variable.

Your article looks at the economics of using premium or regular gas when recommended. No arguments there Data and math clearly show the answer if cost is the concern.

Toss a few premium only cars on the dyno with regular gas and test. Then run them long term and see how they hold up.

I’ll follow the manufacturer’s recommendations. They built it, they know what it requires.


Why post a picture of an Acura fuel door on a thread about Lexus ?

No, I get the point about the important difference between required and recommended. I am making the point that Lexus’ engine, being lower in both power and torque than its peers, yet requiring Premium (which we are taking the OP’s word for BTW), is an outlier in not just its class, bit the automotive world in general. Very few vehicles today require premium. That the Lexus does, while offering no meaningful benefit to the owner is a shame.

Thank you.

Thanks for the reply

Thanks for the reply. If they had told me that I probably would not have bought it.

It’s not the turbo that’ll need repair…it’s the engine.

When ever the manufacturer says “Premium Required”…then do it. Not worth the risk.

Thanks for the reply.