How many of you putting regular gas in your M...and for how long have you been doing it? I'm about to stop fueling up with premium, just wanted to know how others are getting along.

I don't, but I just got my wife a '16 QX60 and have been using 87 for about 2-3k. Want to get a baseline with 87 before I start using premium to see what the difference in MPG is.

I have Never used 87, Used 89 or mid grade and it seems to be worse gas mileage, so the price gets negated. The V6 M35 prolly would react better to 87 than the V8 though.

I'm currently on my third Infiniti, a 2016 Q70 with 16k miles
I had 171796 miles on my 06 G35 6speed when I traded it in for my 2012 G37S 6 speed manual which had 94.4k miles when I traded it in for my present Q70

On all my vehicles I only used regular 87 octane and never had a problem

Telcoman

2009 M35X: I use 87 99% of the time. I only use 91 when I'm filling up my gas cans for my yard equipment. I've done tests between 87 and 91 in the past and have noticed/measured zero difference in gas mileage (23-24 pure highway on trips). Due to the knock sensor there should be a difference(timing advance) if you really put your foot into it, but even here (which I rarely do) I don't notice a difference.

I've used only 87 for over 8 years. Unless you have sophisticated test equipment attached, I don't think it makes enough difference in NORMAL driving to notice. I tried several tests early on, and could not tell any difference. I have never had any knocking, even when heavy footing it. With the price differential, IMO it makes no sense to use anything but 87. Now in my boats, I only use non-ethanol 89.........just to let you know I am not that cheap!

Considering any care for the motors asking for HI-octane , you would do this for the COLDER half of the year (North America '48') , not very nice to engine in summer, whether you THINK you can't hear , calculate , accept what others are guessing , whatever - the excuse to allow ECM to retaard constantly !

I find it helpful to specify what year and model we're talking about.

YMMV, but generally the owners manual is a well-intentioned document whose recommendations are based on a lot of proper testing. I follow that, and it allows non-premium gas for the M35.
I don't expect any anecdotal issues for the V6, but I'll tell you that using anything the wrong octane for the V8 is a TERRIBLE idea.

Once again, if in doubt, refer to the manual. Some related discussion here - which-octane-level-are-you-using-for-q7 ... l#p6780536

I do 80 steady for 35 min each way every day....is that heavy footed? That's really the bulk of the driving I do, I don't know how the anti knock would be affected by that. I'm glad to see nobody has really had issues with 87 grade. I hope to see more input though.

I see the same warnings you lot see: Eventually this will destroy your engine and void your warranty, etc etc. If that was really true, then how do these 'experts' account for the thousands of owners for whom none of this happens? The computers and ECU in your engine will run that engine as well as possible based on the octane you give it to work on. But you won't benefit in any way other than saving about $5-7 per fill up. Thinking along those lines, consider this. That's one cuppa coffee at Starbucks,one fast food lunch, or even one pack of cigarettes. Also, although the engine 'should' account for and perform on regular octane, it cannot run as efficiently, which results in lower power output and decreased mpg ... so your savings at the pump are not as big as you may think. For me, I would give up one stop at Starbucks or one meal at Wendy's and let the car be.
And, as always, if you're on holiday and it's a rental ... I follow Jeremy Clarkson's advise: drive it hard, return if filthy, and use the cheapest crap petrol you can find, LOL.

To clarify my comment above re using 87 octane for 8 years, I am referring to only the M35. No doubt about it, it is an engine specific detail.

SOA is an engineering term , safe operating area - no matter how well the car "adjusts to the inferior gas" ,
AZ today's temp @ 117 F in my shade , even above 98 degrees , your riding a very very thin line, SOA , one foot just making it and the other "riding Detonation" to high hell in your cylinders - IN SUMMER. Some know that's hardly good for the motor , some take the cheaper or easy way out and leave to chance, a free country .

Agreed, I live in TX and the summers can be brutal, I rather use the 93 or premium and have that piece of mind that I'm doing the best I can for the engine