^^^Could mixing different gas types be causing all your "noises, squeaks, and rattles"?

 

Or just use 87 octane. It's probably only under rare conditions that there is any lose of boost. It's certainly not dangerous in any way. The engine management system will quickly adjust for any detonation by first reducing boost and then retard timing to safely run on whatever fuel is in the system. Also any engine will make the most power and be most efficient by using the lowest octane rated fuel it needs to achieve maximum boost that it is designed for. Let's say the NX turbo does best with 91, going higher will not allow for any more power and in fact as the octane ratings go higher power starts to drop off as the high the octane rating, the more difficult it is or the fuel to ignite. The NX may very well run better on 89 as compared to 93 if those are your choices

 

Your assumption is only valid if there is an 87/89 fuel table in the tuning.

My assumption would be there is because of people who CAN"T follow instructions and put the designated 91/93 into the car. However, retarding the timing can only work so far before you have a knocking situation. The need for premium is for boost and compression. Plain and simple.

I legit can't understand why threads like this exist. Or why manufacturers bother putting "premium fuel required" on their cars, not like people listen anyways.

 

If premium is recommended, this is the engine's optimal fuel. It may run on regular—but with the sensor invoking less then optimal ignition setting for a particular combination of engine speed, load—and fuel. And with less than best torque, there will be less performance and a MPG hit.

 

Maximum power may be reduced with fuel rated lower then 91 octane. But unless your pushing the engine to maximum boost levels and higher RPM your unlikely to ever get near the point of detonation. The NX and 99% of every other car built will run perfectly safely for it's entire life on 87 octane fuel. Maximum power max be less but a modern engine can detect detonation and adjust timing for each cylinder at each RPM. I have not tested my NX on a dyno to see any difference however I don't feel anything different. I have tested two other cars that require premium fuel. 2008 VW R32. Made there same exact power, no detonation detected when using 93 octane E10, 90 Octane E0 and 87 Octane E10. That car requires 91 octane.

2013 Mercedes C250 1.8L turbo. Again the car delivered the same power on a dyno using 87 octane or 93 octane. Still hit and held 21.6 PSI boost with no detonation.
Production cars all have to allow for the driver who may be fully loaded with cargo, driving under heavy throttle, in 100° heat and the car be safe. Under many other conditions there may be no difference between 91 and 87 octane.

2006 Volvo C70 2.5L turbo. With 93 octane is held peak boost longer on the dyno. When we went back with 87 octane, it hit peak boost and in a 3rd gear pull was the same as with 93 octane. But when we tried 4th gear which took much longer to reach redline, boost dropped off after a few seconds and power dropped off about 15 hp. And this car requires 87 octane according to the sticker on the fuel filler. But in the manual it says for maximum power premium fuel is recommended.

 

I would like to know where there is still only a $.20 difference, and move there immediately! Right now I can get 87 for my ES at about $1.88-99 a gallon. I just filled up the NX on Premium yesterday at $2.80/gal. This is over the border in Indiana, about 10 minutes away from the BP refinery no less... And that's still considerably cheaper than filling up anywhere in or near Chicago.

 

Most gas stations around here (in the OC) have a 20¢ difference between regular and premium. See the differences anywhere in the country by going to gasbuddy.com.

 

Interesting observation. Come back and post your results if you ever put the NX on a dyno with different octane fuel.

Premium fuel has better detergent package which keeps the engine clean as well other than pure octane increase.

 

No one with any common sense is going to waste their money to rent a dyno for an NX.

 

Just to clear some things up. Detergent and additive packages are the same for all octane levels within each brand. The way it works is a fuel depot stored base fuels, gets an order. he base fuel is the same for any brand and then the additive package for each brand is added, blended before the fuel is delivered to the station.

Also, each additive package cleans certain deposits but tends to leave others. It's actually best to not use the same brand 100% of the time.

For stock vehicle engine management there really are not 93/91/87 octane tables. There is just one table (perhaps 2 or 3 for ECO/Normal/sport modes) and if detonation is detected ignition timing is adjusted. If it continues, timing, boost and fuel settings can be altered to eliminate the pre ignition to prevent any possible engine damage. A modern system and make adjustments on a per cylinder basis and make changes in a single RPM. That's how fast the react. There are some exceptions, such as the Subaru 2.5L turbo in the STI and previous WRX models. They have a much older system with just one detonation sensor and react by changing timing and boost on all cylinders.

Now once you have an aftermarket tune, a lot can change. My last car was tuned to use 93 octane fuel only so a tank of 87 could be dangerous. But power was increased from 240 hp to 289 hp at the wheels.

My friends that does the tuning has recently cracked the Toyota ECU and has began custom tuning Toyota and Lexus cars. I am waiting for the first IS or NX 200t motors go get tuned so we can see what they will do. Some cars have a lot more room for power then others. I know he has gotten huge gains from the Audi RS7 and Maserati Ghibli while the Mercedes Benz C250 (1.8L turbo) can be boosted un the midrange but yields very minimal power gains up top because it uses such a small turbo that it just will not develop more boost then from the factory, the turbo is already maxed out.

Anyway, other then the hr drive, it does not cost me anything to do a dyno pull for one of my cars

 

Also, engine tuning sometimes get very complicated, such as with GM 6.0 and 6.2L cars and the Chrysler Hemi performance cars. Sure, the engine power can be increased but that causes problems for the transmission computer in these GM V8s. So engine tuning has to also include transmission programming. On some Mercedes, the increased boost or power causes the body control computer to throw an error. We had a steering system error code and then an AWD failure code come up on a VW because the engine had been remapped to bring in the variable cam timing to come in sooner to make the engine more responsive. So sometimes remapping the fuel and ignition tables and mean other computers have to be reprogrammed as well so the whole car functions properly.

 

That's why you get a stick

 

Yes, thank you Jaguar

 

And I look at it this way, if you break it or blow it into pieces, you get it rebuilt stronger.

I can't count how many transmissions our race cars have blown up in my lifetime.

 

Here in Houston, Regular is $1.49/gal and Premium is $1.93/gal..... a 44 cent difference. But who really cares. $1.94 for Premium is awesome. Sadly my wife wants to move back to San Diego... everything there is more expensive.