Turbo

Have to agree here. A Juke is very very knock resistant, unusually so for a turbo car compared to say a port injection turbo. The cylinder head coolant passages are extensive and this is one of the contributing factors along with good chamber & piston design, DI injection, piston oil injection, etc. You are knocking then something stupid has been done to the tune or the boost is sky high. I would not purposely run 87 octane as it will default to a less aggressive timing/fuel tune map and that sucks but neither would I fear it blowing up. I prefer Mobile or Shell only, bad experiences with BP fuel.

Timing retard saving an engine.....yes but I wouldn't count on it all the time. The Juke with bolt-on parts I dynoed running 100 octane unleaded and always will despite it's knock resistance. I experienced a fuel system leanout on the Juke from the leaking rail pressure sensor and the stock alternator cutout, luckily the Juke survived it as I didn't detect it right away. I've had a fuel system leanout (other vehicle) due to an overrun speed density map sensor and fuel pump heavily affected by high boost pressures and it's only the 100 octane/xylene/octane booster in the fuel tank that saved the engine when it was hit with a massive fuel system leanout. That got corrected but never on that vehicle would I trust the knock retard strategy to save it as things happen very quickly. Was the high fuel octane that did that. Octane matters a huge amount, so does cylinder cooling.

Fuel additives are snake oil. They are mainly Naptha based, read the MSDS and the dilution ratio in the fuel tank is ridiculous. The induction/fuel cleaning is also pointless. Injectors are properly cleaned with a reverse flow and ultrasonic cleaning using a solvent. Intake carbon deposits require full disassembly or blasting to remove or maybe water/meth injection would help. I had much fun removing this buildup with the head off the vehicle. Despite what you will read the buildup has a lot to do with the natural seepage of engine oil past the valve guide seals.....this is normal for proper lubrication. Unfortunately no fuel to wash it off, thus the deposit buildup. Now OEM are running dual Port & DI injection systems. The OP's problem is undetermined and the Nissan dealership has to figure it out.

I'd like to run Sunoco 94, there's one out near the Indiana border if I remember correctly. Japanese I think run 95 octane or similar.

Should read some of the Sunoco Racing fuel blends. If anyone thinks gas is gas, you will be blown away by the hugely different formulations in their MSDS. We are not talking about pump, this is 5 to 50 gallon sealed drums. The fuels are highly tailored to what boost you are running, static compression ratio, timing advance, type of racing, etc. The formulations are all over the place with different Ethanol %, high oxygenation, MMT additives, Xylen/Toulene %, etc. No, fuel are not all the same. Pump gas no way no how would I trust pushing the limit and never have as it most definitely can degrade. If the volatiles components evaporate off (i.e. xylene/toulene) your octane rating is taking a massive hit, and these do over time. I'd only run 93 octane at a high quality/name brand gas station with lot's of traffic.

Japanese have a higher equivalent octane rating than us, even considering the MON or RON differences. Their 100 RON octane is equal to 95 AKI octane in the U.S. and their 98 RON octane is about equal to our 93 AKI octane. Slightly higher but still higher and useful. AKI = (RON + MON) /2.

The Sunoco link shows the correlation between MON, RON, and AKI ratings. Huge differences in fuel types and formulations. Basically a Naptha, Toulene, Xylene, Ethanol, maybe Methanol, & MMT, etc type blend. The SDS if you are a chemist is an interesting read, especially the highly oxygenated fuels. Lot's of stuff that can evaporate off or absorb water over time, thus the aging factor. Highest unleaded is about 105 AKI (110 RON/100 MON) and basically has any and all of the above minus lead. That is how you basically get above 87 octane more or less these days on unleaded. Xylene/Toulene (i.e. paint thinner) will pretty much dissolve deposits which is the main ingredient in fuel cleaners, except at a ridiculously low concentration. You can pretty much buy Xylene/Toulene at Sherwin Williams or online and run some of that in your tank at up to 20-30% max mixing ratio and it will definitely start cleaning out the injectors like no other fuel cleaner ever will if you are brave enough. Costs mucho bucks to run high octane so unless you need that it's basically wasted.

A good link: