Is premium fuel really needed?
In a forced induction car, 87 will work, but you have considerably more power with premium. Try it in your nx and you will see, its way down in power, especially at highways speeds. I get around this issue by getting my gas at Costco, which makes premium just a tad higher than standard gas at shell. In my is350, the difference is minimal, but i tend to drive a bit more aggressively so response does change ever so slightly. In either case, hard to believe you will do any damage or blow and engine by using a lower grade of fuel. This would cause all sorts of issues and lawsuits when you end up getting lower quality premium gas, or winter premium in the midwest. As someone stated ford does list 2 different power numbers for regular vs premium on their ecoboost engines, and if you dig deeper the ecu on fords actually has separate fuel maps for high octane and low octane fuel.
Pole Position
Joined: Jul 2015
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From: Texas
In a forced induction car, 87 will work, but you have considerably more power with premium. Try it in your nx and you will see, its way down in power, especially at highways speeds. I get around this issue by getting my gas at Costco, which makes premium just a tad higher than standard gas at shell. In my is350, the difference is minimal, but i tend to drive a bit more aggressively so response does change ever so slightly. In either case, hard to believe you will do any damage or blow and engine by using a lower grade of fuel. This would cause all sorts of issues and lawsuits when you end up getting lower quality premium gas, or winter premium in the midwest. As someone stated ford does list 2 different power numbers for regular vs premium on their ecoboost engines, and if you dig deeper the ecu on fords actually has separate fuel maps for high octane and low octane fuel.
Intermediate
Joined: Jul 2011
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From: Ohio
Pole Position
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From: NY
I think Lexus recommends premium on the NX because that's what's needed to achieve stated MPG and performance.
Using lower grade gas probably won't harm your car but you'll suffer mpg and performance losses.
Has anyone been using 87 for awhile (at least a year) and can tell us their experience?
Using lower grade gas probably won't harm your car but you'll suffer mpg and performance losses.
Has anyone been using 87 for awhile (at least a year) and can tell us their experience?
Pit Crew
Joined: Nov 2015
Posts: 131
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From: Ontario
I think Lexus recommends premium on the NX because that's what's needed to achieve stated MPG and performance.
Using lower grade gas probably won't harm your car but you'll suffer mpg and performance losses.
Has anyone been using 87 for awhile (at least a year) and can tell us their experience?
Using lower grade gas probably won't harm your car but you'll suffer mpg and performance losses.
Has anyone been using 87 for awhile (at least a year) and can tell us their experience?
Pole Position
Joined: May 2013
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From: Idaho
I haven’t commented on this thread as I have the hybrid so I don’t have the vibration issue some here have reported. However, I will say the octane definitely made a difference in how smooth a former Audi idled.
I know modern cars compensate for the different octanes but do they run smoother if they don’t have to compensate? Again, the hybrid doesn’t recommend premium so I am just curious and not trying to express an opinion or set off a fresh debate. Is it reasonable to assume the manufacturer’s recommendation represents the conditions the car was tuned for and likely will yield the best results? Just pondering...
I know modern cars compensate for the different octanes but do they run smoother if they don’t have to compensate? Again, the hybrid doesn’t recommend premium so I am just curious and not trying to express an opinion or set off a fresh debate. Is it reasonable to assume the manufacturer’s recommendation represents the conditions the car was tuned for and likely will yield the best results? Just pondering...
Lead Lap
Joined: Mar 2015
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From: America
That AAA study shines light on "recommended" not required. So this does not really help our case much. The NX runs a turbocharged 2.0L inline 4 cylinder. This spells out high compression and high heat. Heat causes knock, the fuel spontaneously ignites. The RX hybrid is a naturally aspirated 3.5L V6. This spells out mild compression, Less heat would be created from the compression stroke on this engine.
I use premium during the summer but mid-grade during the winter. With outside temps around 30F, I don't see the internal cylinder temp raising the air fuel mixture high enough to knock. But to each their own. I can tell you that Lexus wants premium in the tank. Pg 392 of the NX manual states that if a octane of less than 91 is used it can result in engine damage and a voided warranty. Lexus also states that if only low octane fuel is available that the vehicle should not see heavy loads until refueled with higher octane.
I use premium during the summer but mid-grade during the winter. With outside temps around 30F, I don't see the internal cylinder temp raising the air fuel mixture high enough to knock. But to each their own. I can tell you that Lexus wants premium in the tank. Pg 392 of the NX manual states that if a octane of less than 91 is used it can result in engine damage and a voided warranty. Lexus also states that if only low octane fuel is available that the vehicle should not see heavy loads until refueled with higher octane.
Last edited by skyshadow; Dec 21, 2017 at 10:02 AM.
Lexus Champion
Joined: Sep 2016
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From: AB
That's funny. No one talks about GDI which causes carbon build up on intake valve and cylinder head. Difference in Octane value aside, premium gas has more detergent. If one wishes to own the vehicle long term with GDI engine(most of them in today's small engines) Using top tier premium gas is desired. Our cars in the family all require premium. We only use Shell premium. In the case of my car, Audi SQ5 when I tried to use lower octane gas, I got a DTC code of cylinder
1 mixture imbalance. Back to premium gas and reset the code which never came back. It is your car, do whatever you want. That's the way I see it.
1 mixture imbalance. Back to premium gas and reset the code which never came back. It is your car, do whatever you want. That's the way I see it.
Lead Lap
Joined: Mar 2015
Posts: 423
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From: America
ANYWAYS, what I'm saying is if your car does not recommend or require premium, you are doing it no favors by putting premium in it. The car has restraints on how far it can advance and if it was not engineered around premium, it will not be able to advance enough for it. And that's the only thing "premium" fuel is doing. Again, it is not cleaner or "better" in any other way.
Driver School Candidate
Joined: Apr 2015
Posts: 30
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From: ca
^ your last statement I agree with. But if it's recommended or required, just go with it. It's kind of like the pointless oil threads on BMW forums. Some guys want to save a few bucks every few months by finding an alternative. Just buy the correct damn oil that the engine was specified for and designed for using. It's not that huge of a cost savings.
Lexus Champion
Joined: Sep 2016
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From: AB
^ your last statement I agree with. But if it's recommended or required, just go with it. It's kind of like the pointless oil threads on BMW forums. Some guys want to save a few bucks every few months by finding an alternative. Just buy the correct damn oil that the engine was specified for and designed for using. It's not that huge of a cost savings.
this issue. If one says no difference running different grade gas I wonder what kind of driver you are. I like snappy, smooth running car than rough, sluggish one.....