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I'll be picking up my JX in a couple of weeks, and I noticed the manual says "premium fuel recommended". The manual for our current vehicle says "for optimum performance, use premium fuel", but we have been using 87 octane exclusively for the last two years with no issues. I already found out it won't void the warranty by using regular unleaded, but I'd like to get some thoughts from any current owners if they are using regular or premium and if they notice any difference in performance. Obviously, the way gas prices are right now, I'd like to get away with using regular if I can, But I will bite the bullet and use premium if I find that it is measurably better for the vehicle. Thanks
 

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I use the premium, if your spending over a $50,000 for a car might as well put the best possible fuel in it! I personally don't want to take a chance by the regular fuel doing any damage so I use the premium.
 

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The high performance of Nissan engines used in Infiniti have a high compression ratio. Using premium (high octane) fuel allows it to operate in its mid-bell curve. The fuels sensors once detecting a lower octane fuel will set its computer setting to retard-delay the timing of ignition to prevent knocking at that compression ratio. Hence, at that setting, the operation is not at its mid-bell curve. I just don't know at what level of engine running demands will that "outside-of-the-mid-bell-curve" show knocking, lower output, etc. when regular 87 octane fuel is used. I would strongly opine to use premuim high octane fuel for this reason. :)
 

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It'll work with a lower grade but it's not healthy for the engine. If the engine was tuned for premium then it should be using premium. It can use regular in an emergency but it's not recommended. Use premium and your car will last longer.
 

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Dealer said you can use regular instead of premium. You lose 6 horsepower.

Mine is a 36 month lease so I could give a sh$t about lasting longer. I guess this is for a different thread but with over 60 % residual I don't understand why you would purchase instead of lease? But I always lease.
 

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Use the fuel in between. If recommended is 91 octane then you can try using 89. 87 might be too low, car will run shitty.
 

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When I test drove the JX, we had to stop off at a gas station for more gas. I was surprised to see that the salesman used 87. He said that it was corporate policy for their Infiniti dealerships to use 87 on all of the Infinitis on their lot!
 

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Anyone read the manual? :) Talks about using 87 in the rare occasion you can't get 91. And that too, it advises you to fill upto half a tank for emergency.
 

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As G37X-JX35 stated above, the engine will automatically compensate for the fuel grade you buy. High octane does NOT equate to quality. It's one of the biggest myths running, right up there with the 3k/3m oil change.

The ONLY change you'll see is a small hit to economy. There is no harm to the engine.
 

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Only reason for premium is to minimize detonation given the high compression. If the sensors detect any detonation, it automatically pulls timing thus losing some HP (minimal). There's no octane sensor on the vehicle btw, if it makes you feel more comfortable use premium during hotter months (if in hot climate region).
 

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It all comes down to the engine you have and if's it an high output/high performance engine for it's class. Usually most 4 cylinders and 6 cylinders use 87, once you step into V8 territory 91 octane is recommended.

Using 87 in a high output engine can do some serious damage in the long run!
 

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Actually it's the opposite. Engineers usually try and squeeze more performance from smaller engines. With this you need to precisely control fuel detonation, thus higher octane.

Technically, the lower the octane,the quicker it will ignite under pressure.
 

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Here is the label from the fuel filler door. 2013 JX : Premium unleaded RECOMMENDED for maximum performance. I take that to mean that it is OK to use regular unleaded, but you won't beat another JX off the line that has premium.

On my 2007 G35 S Sedan : Premium unleaded fuel ONLY. I think the that same 3.5 liter engine is even higher compression for max performance at 306 HP, so it requires Premium.

The JX engine is the same basic 3.5 liter engine but only 265 HP, so I don't think the compression is so high that premium is a must. I bet you can use regular unleaded on CVT sport mode and get similar performance to premium unleaded in CVT normal mode.
 

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Here is the label from the fuel filler door. 2013 JX : Premium unleaded RECOMMENDED for maximum performance.
Thanks for the additional details. This exact same wording is used in my 06 M35. For the last 6 years I've used regular fuel without a single knock or problem. Again, the motor will correct against octane levels.

I'm sure if I use premium the MPG will bump along with horsepower. Since I'm not an aggressive driver the HP hit has never been noticeable.
 

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I'm using premium and plan on continuing. My thoughts at premium gas cost 5-10% more right now. If you loose 1 mpg (just a guess) using 87 octane then your loosing about 5% in fuel economy so its almost a wash.
 

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The new motors, really do not make a difference it will jsut adjust to the octane you put into it,m unless because where you could only run one octane.
 

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Actually it's the opposite. Engineers usually try and squeeze more performance from smaller engines. With this you need to precisely control fuel detonation, thus higher octane.

Technically, the lower the octane,the quicker it will ignite under pressure.
^^ he's got it right.

There are actually more and more small engines requiring high octane because of their high compression ratios and high efficiency.
 
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