Copying my post from this thread: https://www.jukeforums.com/threads/premium-vs-regular-gas-debate.117910/page-37#post-2663210
I still can't believe this conversation is continuing. Octane rating is a means of measuring the fuels resistance to knock. You can run 87/89 (US grading) fuel in a juke without issue. Unless your beating the snot out of the car, or tuned for more aggressive fuel, it will not hurt anything. OEM's always recommend higher grade fuel as a form of butt protection. Call it plausible deniability. Also, note the key word. RECOMMENDED. Not REQUIRED. A Ferrari REQUIRES premium. It is a sports car. Tuned for power. A GTR REQUIRES premium. Same logic. If you don't believe me, go stand at a local gas station for a day. Take down the vehicle, and the octane selected. Then look up how many vehicles that day recommend premium vs how many people used it. OEM's would not dare sell a vehicle that could not safely run on cheap fuel. That's just asking for a nightmare. Unless your Subaru in the early 00's. At that point you just hope the engine will run a mile up the road. But I digress.
During normal driving, the combustion chamber does not get hot enough to cause pre-detonation. Even if you have absolutely terrible quality fuel in the tank, the crapiest spark plugs known to man, or 2mm of carbon on the valves, the ecu has the ability to predict a detonation event before it happens but use of the knock sensor listening for un-natural combustion that can lead to knocking. If you look at the ECU doing a knock count, you can see it does not pull any ignition timing until you are well above 1000 units.
The ECU also has the ability to pull as much timing as needed to stop knock from happening. On our shop test car we have been able to get the ECU to pull 9 degrees of timing as part of a rev experiment we did. The same car was able to make 350 wheel horsepower on 87 octane fuel with no additives. Not that we recommend this or would ever keep a car like this, as eventually it will knock pretty badly during a real world pull. But it is do-able in a controlled environment.
Also, if you look at places like California, They do not even have access to 93 octane fuel, and in some areas you cannot even get 91. So if running a lower octane fuel was going to blow cars up, don't you think there would be mass engine failure in those areas?
I work on and interact with a lot of jukes and juke owners. I can PROMISE you that 95% of them have never put anything higher than 87 in their car and they run totally fine. I don't think I have met someone who drives an un-modified Juke that I do maintenance on that has ever used 93. I may start asking people as they come in so I can get hard data on this.
When money is tight for me, I even put 87 in my Juke. I load up a tune I have made that's very conservative, so around OEM, and run 87 until I feel financially able to put 93 in and load up more power. And that's a car running a massive turbo.
the V1 is a 9.5:1 compression ratio. The V2 is a 10.5:1. But the compression is not what causes knock in this case, it is the addition of nearly 1 atmosphere of boost and high revs that can do it. Most modern NA cars run compression ratios much much higher than this, and you see those cars getting 87/89 every time you drive by a gas station.
So again, the only time premium fuel is RECOMMENDED is in the following situations;
-Hard, aggressive driving. If you have a lead foot and are doing WOT pulls every chance you get.
-High altitude driving. Reduced oxygen in the air can throw off fuel mixtures, so you want to reduce the chances of a lean condition causing knock.
-Towing. Engine loads are always much higher and engines run a lot hotter when doing this. But you should not be towing in a Juke anyway.
-Tuned specifically for performance. If you have been tuned on 91/93, you MUST run that fuel. Your tuner more than likely ran the car to the bleeding edge of what the fuel can handle at your power level.
If the car is just getting commuted and driven like 99% of people drive their cars. 87/89 is fine.