Octane level for 2.5 Skyactive in M6

According to the marketing info, this motor has a 13:1 compression ratio- more than 20% higher than a 428 Cobra Jet! Yet it runs perfectly well on regular 87 octane fuel, generating an advertised 184 HP. With other manufacturers' technologies, knock sensors retard ignition to reduce pre-ignition at the expense of power and efficiency. Does that happen with this engine? Will higher octane fuel enable the 2.5 to produce more power due to a more advanced spark curve? Does "Sky Active" use a different technology to prevent pre-ignition?

I've been wondering this too. The Hyundai/Kia 2.0T both the ones on the Sonata/Optima and Genesis Coupe do adjust as far as I know and so does the 1.6T on the veloster Turbo and the upcoming Kia Forte SX koup/hatch as well as the 3.8 on the Genesis. The 2.0T on the Subaru Forester is also reported to also adjust on a Motortrend article and to get the 250hp you have to put 91 or higher I believe.

It really is a good question. It has come up before. No offence, but the USDM CX-5, which features the same 13:1 compression ratio, has been on the market for well over a year now. It is designed to operate on regular gasoline. No issues from owners operating their 2.0l S-G CX-5 on 87 octane. I have had mine since March 2012, and it now has over 20K miles, with nothing but 87 octane ran through it. It runs great.

As far as engineering used in their design, they implemented a few temperature reducing elements, in order to avoid knock. These parameters include: direct fuel injection (atomized fuel actually cools the charge), a cavity on the piston top (cavity contains high temp initial ignition below plug), a high flowing 4-2-1 exhaust manifold (ensures hot exhaust temps evacuate the cylinder as quickly as possible), reduced engine friction, and electronically controlled variable valve timing, for quick a precise timing adjustments. Generally, the longer exhaust gases remain in the cylinder, the more heat that is transferred into the engine components.

I think you’d be wasting your money by filling up with mid grade, or premium. There would be no performance benefit. The only possibility with premium would be better assurance that the knock sensor wouldn’t “hear” pinging, resulting in knock retard of the timing advance.
Just make certain that you buy good gasoline. With 87, there’s not a lot of leeway, if you do happen to pump in a bad batch of gas.

Just asked about this in my newbie post.
Was curious about the same thing with the high compression. I know the Camaros, when they first came out, said regular, but you got a little more power & better performance with premium. But, that's a sports car, & a 6.2l V8.

The 5.0 in the Mustangs do the same as well, they drop by like 10-15hp with 87 and so do a couple Hyundai/Kia engines though I'm not sure how reliable their hp figures are but I'll put them anyways; Gen coupe 2.0T: 274hp with 91, 260hp with 87, 3.8: 348hp with 91, 344hp w/ 87. I heard the 1.6 in the Veloster Turbo does the same thing as well The new Subaru 2.0 DIT does the same thing from what was written in a couple first drive reviews including Autoblog's and Motor Trends, 250hp with 91, and 220ish with 87, though if I had the Forester XT with that engine, I sure as hell won't put 87 on it. There should be a couple engines that adjust depending on the octane of gas you put in it, so far these are the only ones I know of plus the Camaro.

Edit: I just looked up the owner's manual for the new 6 and this is what it said:

"Your Mazda will perform best with fuel listed in the table.
Fuel Octane Rating*
(Anti-knock index)
Regular unleaded fuel 87 [ (R M)/2 method] or above (91 RON or above)
* U.S. federal law requires that octane ratings be posted on gasoline station pumps.
Fuel with a rating lower than 87 octane (91 RON) could cause the emission control system to lose effectiveness. It could also cause engine knocking and serious engine damage."

There could be benefits but somebody's gonna probably need to dyno their car with a tank of 87 and 91 back to back to know if there's any horsepower gains/losses

The point of my original question was to see if anyone knows details about the technology that allows 87 octane to run with a 13:1 compression ratio without knocking. So far, I've seen that the direct injection, piston design and exhaust header are designed to run cooler and draw off heat faster. Since retarded ignition timing creates more heat, there must be another technology to prevent pre-ignition.

we put Kwik Trips 91 octane in out '13 mazda 3 and the milleage went from about 33 to about 35 mph and the car seems to feel more snappy too.....there 91 is ethanol free to which helps the economy.

its just like fords advertised "piston cooling jets"....direct injection is the technology in conjunction with the piston design that allows for it.