After reading all of the posts in this thread, you seem to be the voice of reason. In my opinion, you're just playing with fire if you don't use Hi-Test (Premium). Eventually the knocking WILL damage something in the engine.

I tend to believe engineers & mechanics over buddies and self-schooled experts.

Is it really worth it to take a chance with a $40,000 automobile to save a few bucks by putting regular gas in your baby, just because you can't hear or feel a difference? A Turbo charged high compression engine? My vote's with the majority.

 

There are knock sensors in the engine and the ECU will alter timing and boost if it detects are knocking. You can safely use regular fuel for the cars entire life with no ill effect except for reduced engine power under some conditions. Some engines are more sensitive, require premium or boost will drop off. Other cars may only require premium under specific conditions, such as under heavy load in hot conditions.

Some cars I have tested include a 2008 VW R32, requires premium. I dyno tested the car with 87 octane E10, 93 octane E10 and 90 octane gasoline. Found no measurable difference when using each fuel. Same for a 2013 Mercedes Benz C250 1.8L turbo. Engine power was the same with 887 octane and 93 octane. What was interesting is when testing a 2009 Volvo C70 w 2.5L Turbo I5 engine. It requires 87 octane fuel. However while it ran fine with 87 octane, that car made measurable more power with 93 octane fuel. Boost levels held higher into the RPM range with 93 octane instead of dropping off lightly as it did with 87 octane.

I have not dyno tested the NX but I am guessing that using 87 octane fuel may cause the ECU to cut back ignition timing or possible drop boost pressure under hot difficult conditions, such as towing or highway driving with a heavily loaded vehicle (4 people) etc. Damage to the engine is not likely

 

This issue was discussed extensively about a year ago here. I actually started the thread.

If your interested in reading the thoughts and opinions click on this link,

https://www.clublexus.com/forums/nx-...ular-fuel.html

I ended up using the blended method suggested by Corrado when premium prices were high, but when the prices bottomed out I used premium exclusively. Now that prices are inching back up i will have to consider blending again when they get into the 4 dollar range.

 

After reading all of the posts in that other thread, my thoughts go back to our Gas Cap label which states: Premium Unleaded Fuel Only. The chance that I could void my warranty or POSSIBLY harm the car by using lower octane fuel kinda ices it for me.

Those, and other comments made by thoughtful posters outweigh the possibility that I MIGHT not be causing harm to the engine. The two sides make some good arguments, but to me, it's just not worth the risk.

 

I forgot to mention that there was one poster who is very knowledgeable but doesn't know how to communicate in a civil manner dominated the thread. He has since traded in his NX. I thought there was enough good info to link it but as I said I was sorry I asked the question.

Bottom line, it's up to each owner to make his own decision based on the info at hand.

 

While everyone has opinion, there is one thing all experts agree: use the grade manufacturer recommends.
We used premium in both RX even tho regular recommended.
I felt it burned cleaner, especially since I had a fuel part replaced under warranty early on. Service said I was using bad fuel. Never had issue again with premium on RX.

 

The octane rating does not have anything to do wit hate quality or the cleanliness of the fuel. It's just the ratio of heptane to octane molecules. The Octane rating is not a physical measurement of the ratio, but of an equivalent resistance to igniting. In fact most brands of fuel all start off from the same storage tanks and the distributor adds the correct additive package before delivering the fuel to the gas station based on the brand they represent.

 

I would inject here that the experts I've read say that using higher-octane fuel than required is a waste of money. But it is your money.

 

Best advice right here. The regular vs. premium discussions go on all the time with most brand/models normally with no resolution or agreement.

 

This and This.

Lexus' official rating in the User manual and SAE filings for the engine calls for RON 91 rated fuel. This is a specific method for measuring octane level in gasoline. There is another method for measuring octane, it's called MON, and that one uses the RON method but adds specific operating characteristics in the measurements.

Then there is the gasoline companies in North America, and they use yet another number to "market' the gasoline and their rating is an average of the RON and MON numbers called AKI.

For US/Canada:

AKI 87 is equivalent to RON 91 (marketed as Regular in NA)
AKI 91 is equivalent to RON 93 (marketed as Premium in NA)
AKI 94 is equivalent to RON 95

Cleaners and detergents have to meet a minimum requirement anyway. Rely on facts and data but ultimately use what you feel comfortable with.

 

On the topic of fuel and sorry if I'm hijacking the thread, but for those in the US, is Costco branded premium gas okay or is that a no no?

 

we've been using costco fuel for over 10 years in our Lexus;. Just need to get there when they open at 6am to avoid lines.
As someone else stated, all fuel is from the same 'faucet'. Each brand adds minor additives in order to advertise something special.
Most important is how the fuel tanks are being maintained/tested, which I want to believe Costco does.

 

If you refer to your manual(heaven forbid), there is a whole page devoted to Fuel information.

See page 599, it refers to the use of Top Tier Gasoline which Lexus recommends. There is a web site listed to go to and you find what gasoline retailers meet the standards. Costco is listed.

Also, on that page,

Lexus says,
octane rating 91 = RON 96
87 = RON 91

 

I've been using Costco gas for years. Costco is considered a "Top Tier" fuel provider. You can look up Top Tier providers online (as someone had mentioned) or use the "Gas Buddy" app on your smartphone—it shows if a particular station is Top Tier or not.

 

I would even dare to say that Costco gas station is better because they maintain the pumps on a regular and frequent basis unlike other gas stations. They change the filters quite often, and constantly check the pumps to make sure no one has tampered with the card readers. At times, they stand there with stopwatches to measure the rate of flow. They are also rated as a Top-Tier gas station like Chevron and 76. Just because they are significantly cheaper than outside stations, doesn't mean they are delivering a subpar product. Kirkland has high standards for all their products.

The only drawback is the long lines...I usually go after 6:30 and the lines are quite short.