I have been testing 87 octane gas in my 2012 QX56.

Before someone says some BS like "if you can afford QX56, you can afford premium"... True, but premium here is about 40% more than 87, so if the vehicle can use 87 I essentially get to increase my MPG by about 40% (20 to 28 on highway) for free. That's like going from a 6,000 pound behemoth to a sedan.

So, after over 1,000 miles, I have found the vehicle runs perfectly fine with 87 and gets the same MPG on the highway - about 18MPG going 75MPH cruise. In fact, if anything, 87 seems to get slightly higher MPG, but I'm going to say it's within the margin of error. I did not test city because it's harder to get an apples-to-apples comparison in stop and go city driving with different routes, traffic, etc.

Has anyone done any tests like this or used 87 for an extended amount of time?

you are opening up a can of worms and digging a rabbit hole.

yes you should use high test in this engine. its on the petrol door and in the operator manual. if you wanted to use 87 you should have picked up an armada.

ill chime in but note this is my opinion:

the car is designed to get its peak efficiency and power off high test petrol.

the car can run fine on any unleaded octane rating--the computer will simply adjust timing. this is true for any modern car with a computer running the engine.

sure you are getting a savings by using 87 octane. its cheaper than high test. the car , as mentioned, runs just fine because timing is retarded and other things are adjusted to keep the engine running at that octane.

i would not use 87 for extended times in the engine because the tolerances and compression are much higher in this engine because its a higher performance engine and low octane can cause more engine knock as the engine gets hotter and as ambient temps rise. sure the computer will just retard the timing more if it hears the knock but now your performance is suffering and you can potentially cause some engine dame due to the increased knock.

in the end its your money and your car. you can do what you want. you will get varying degrees of opinions on this as as other chime in.

My first QX 56 - 2006 Purchased NEW ..I just Traded in with 294,348 miles.....and everyone on REGULAR GAS !!
Because I like that body style I just found a 1 owner 2010 QX 56 that I purchased. Plan to use the same ole regular !!

In my life as a 2006 owner,,,,the only major repairs (not counting suspension) were exhaust headers...(Infiniti flaw covered up by factory denials) right rear wheel bearings (twice...my roads convex/concave will cause this) (not the left side ever)...BTW...sparks plugs changed @ 125,000 and 250,000....I do change gas filters every 35,000 no matter what gas supplier you use...they all need to be filtered !! 87 forever pal....

From what I have read there is difference between premium "recommended" and premium "required".

Here is an excerpt from an article I found on Edmunds.com. They have a list of vehicles for premium-recommended and premium required cars.

...It's a different story for a car whose engine requires premium fuel. The car will still run on regular fuel in a pinch, but you shouldn't make a habit out of it. The fuel's lower octane can result in elevated exhaust-gas temperatures and possible knocking, both of which can adversely affect the engine's health in the long run. Running regular-grade fuel in a car that requires premium might sound like a good way to shave a car's running costs, but the short-term savings won't come close to offsetting the cost of repairs to a damaged engine...

https://www.edmunds.com/fuel-economy/to ... emium.html

Any car with an 11+ compression ratio should be ran on premium. With emissions requirements they are already running on the edge of lean and pinging, so why even risk it? Both my cars are 11+:1 compression, I would not dare put regular in.

Page MA-13 of the service manual for the 2010 QX56 calls for an octane rating of at least 87. No mention of premium fuel.

the car can run on 87. thats never been debated.

mac , yeah and one thing the people who THINK regular is hunky dory can do what savvy tuners here ,AZ do
and go to 1 colder on an Irridium plug ,because the RETARD conditions are magnified when using a "Lesser than Recomended Octane"( as virtually everyone above is saying in their "own words" ) and at least the cyl's are not as "constantly" pushing the DETONATION ENVELOPE ! G 2/25/2018