No offense dave but unleaded higher octane(94-100) might be a waste of money, but I have never seen it hurt performance. I have been on and to many dyno sessions and I have never witnessed nor heard of such a thing. You can pour a few or more gallons of higher octane in and as soon as the ECU adjust to it you will normally see an increase in power and performance.

 

From my experience I did once put 101 Octaine and I didnt really notice that much of a difference, the car was a little smoother upon acceleration. The guy at the gas station told me its fine to put 100+ as long as its unleaded and the engine can handle it. He also mentioned that he hear many many porsche and bmw owners saying that it actually works and what not.

 

Thanks for all the feedback. Silly me, I forgot to see if it said Unleaded. From what you guys say, 110 probablly isnt. That is the only fuel station I know of that sells higher than 93. If I ever find another with Unleaded, ill give it a try.

 

I just filled up with BP Premium and prefer it way over Shell V-Power..... Didnt like the shell gas at all... car felt less powerful and sluggish...

 

I've always had the best luck with BP in my cars. In Kansas City, the highest octane I can get is 92 and that's at BP. My G35, prior Maxima, and my wife's 98 Legacy GT get the best MPG and driveability with BP fuels plus a majority of thier oil doesn't come from the Middleeast.

I've ran Shell V-power in my Maxima and I got quite a bit of audible pinging and sluggish response. I had a JWT ECU installed on the car and apparently the ECU didn't take kindly to the Shell gas. I've run a tank of Shell gas through my G35 and the car didn't feel much different, but I did get worse gas MPG. If I have the option, I will run BP all the time. My cars just seem to run better on it.

Experiment with all the big name brands and see how the car feels and what kind of MPG you get. Different makes of gas really can impact how a car drives.

 

A VQ or other higher performance motor seems to be able to take advantage of the additional octane, to a point.

Running too high an octane will hurt performance. There's no way around it. Running 110 in a VQ will result in less power because the 110 octane requires a lot compression/heat in order to ignite. It would be like running 2 to 3 step colder plugs in your car. It's going to hurt performance. When you don't have proper ignition/compression/heat, the fuel doesn't burn correctly if at all plus timing can get thrown off because of the inconsistent burn.

There is a fine line between running too little octane and too much octane.

 

I tried a number of different company's and BP 93 seemed to give the best performance and gas mileage. If I use higher octane I like to use the Sunoco GT 100 unleaded every once in a while, but I was driveing a turbo car before and that helps eliminate knock at higher boost If I went to the race track it was overkill, but I used the C16 for safety due to the fact I was pushing the engine harder and I wanted the extra protection from detonation.

The LEADED octane fuels WILL damage your O2 sensors and catalytic converter over time. I have witnessed this personally with two brand new sensors going bad from just 2 trips(2 full tanks of C16) to the race track and the catalytic converter went about a couple months later. Hope this helps.

 

I can see where 110 would be overkill on the VQ, but I dont think a little 97 or 100 unleaded will really hurt you. I have witnessed it many times and not just on turboed cars but on NA cars too by dumping in a few gallons, WHP will go up. We are not talking about 20 hp here. Im talking about 3-15hp depending on the car and whether its forced induction or NA. If you have it on the dyno and do some base runs and then dump in some 100 octane it will bring your octane level up from whatever it was before by a few points. You should see better gas mileage and a slight(notice I said slight) increase in perfromance. I cant remember how the equation works but here is an example. I dont know if my #'s are precise but you get my drift.

6 gallons of 93 + 3 gallons of 100 = 95-96 octane << not exact just a example

I will try and find a chart that shows the value if higher is added. I cant remember where I seen it.

 

I stand corrected. You and dave are right to a point. I found this doing a search, but it does say with the compression of your engine you might be borderline between two octanes so useing the higher could benefit you. Manufacturers also put the lowest rateing you can use on the car and useing a slightly higher rateing should not hurt you. Im not saying to go out and dump a full tank of 100 in, but putting a few gallons to a almost full tank should not hurt you. Here is the info that I found.
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"The octane rating is the measure of the fuel's resistance to autoignition. When autoignition occurs the gas pressure wave it causes superimposes on the normal pressure wave of the combustion chamber. These two waves interact to create a third sawtooth-shaped wave pattern of pressure oscillations. The pressure oscillations create the knocking sound. Pressure waves caused by knock can build up quickly and shorten the life span of an engine.

Knock can be reduced by adding chemicals to the fuel. Common examples are tetra ethyl lead, aromatics, and oxygenates. While these substances increase the octane rating, their composition does not contribute to the energy of the fuel when it is burned. The result may be less energy per unit volume of fuel used, and thus less efficiency. In short, higher octane fuels may require more fuel to be burnt in order to produce the same amount of energy. But wait! Didn't I say at the beginning that we experienced a gain in power and fuel efficiency?

There is one piece of information we have been missing. The compression ratio of an engine has a lot to do with knock and the apparent effects of octane. Compression ratio can be thought of as the pressure in the combustion chamber. High compression ratio engines have more of a tendency to knock than lower compression ones. Given what we know, since a low compression engine is not as likely to knock, it does not require a fuel with as high of an octane rating. A high compression motor, however, needs more octane to reduce knock. In such a case, switching to a higher octane fuel would reduce the effects of knock, leading to a more efficient combustion process. This creates more power and better fuel economy. Using a higher octane fuel in an engine that does not experience knock will not help performance. In fact, if the higher octane was achieved through the use of oxygenates, higher octane than necessary may actually hinder the performance of an engine!

The goal, then, is to find a fuel with an octane rating that is high enough to prevent knock, but not much higher. It is possible that the tiny performance boost we experienced with the drag car is related to the use of the higher octane fuel. The compression ratio of our motor may be a borderline case where it is able to use the slightly higher octane. Sunoco 116 would not help our relatively low compression motor any more than the Sunoco 94, but it is a necessity in most of today's extremely high compression race engines. In fact, at over $4.50 per gallon, Sunoco 116 would do nothing more than drain your wallet faster! Technology is not cheap.

WARNING: Use extreme caution when attempting to use a fuel with a lower octane! If the octane you use is too low, knock will occur, and your engine can be damaged. Follow your manufacturer's guidelines as to what octane is suitable for your vehicle."
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So basically if it says to use 91 octane on your car and you put in 92-93 I think you should be fine, but dont dump in a full tank of 110 or its just a waste of money. Its mainly to protect against knock and detonation which you shouldnt have any problems with unless you do forced induction or raise the compression of your engine.

Like I had said before though, I have personally witnessed it on many dyno sessions where just adding the higher octane(raiseing the octane level) to the mix yielded more WHP on the dyno, so I dunno.

 

It would be nice if someone could get a dyno shop to do some testing between 91-100 octane but thats alot of time, money, and effort. It would be very interesting to see the performance difference between the octanes and at what point the octane level would be a waste of the money.

 

I totally agree. If you read some of my prior posts, I allude to the fact that I believe the VQ can take advantage of the higher octanes and that I plan on running 95/96 octane (overall) in my G35 when I go to the track. SCC saw an increase of 8-10whp by going from 91 octane to 100 octane in their project Z. I think 100 is extreme and that 95/96 should reap most of the benefits.

You're not going to hurt anything by running high octane assuming that it's unleaded, but the performance may not improve.

As for damaging the engine by running low octane, it was true for older cars, but not now.....assuming you don't have aftermarket forced induction. The VQ motor is equipped with a knock sensor. When knock (detonation) is sensed, the ignition timing is retarded and the fuel mixture may be richened. Richening the fuel mixture is a quick way to cool off compression chamber. If you run 87 octane, the motor may experience more knock, but the knock sensor will compensate for it which basically means your power and MPG will go down. I know that with the 95-99 Maximas, running 87 octane vs 91 octane will result in a 10-15% loss in power. If the knock sensor fails (common problem), the ECU will revert to a preset ignition map which means a 15-20% reduction in power. WOT timing advance goes from 22-24 degrees to 13-14 degrees. That's pretty severe.

Nissan knock sensors are very sensitive hence the reason why higher octanes fuel do make a difference in performance. Spec V Sentra guys have gone as far as relocating the sensor to the firewall........which is just stupid and proof that the internet sometimes isn't the best source of information.

 

Wow there is a lot of info posted here. Much of which I cannot understand =)

Ill try BP when my gas goes empty and will post what I feel. Ive been using Mobile 1 93 and I thought BP, which offers 92 top, was worse just because it said 92. From what I read here, 91 and up is ok. Supposedly, there is a chance that BP 92 can feel better than the fuel I currently put in (Shell 93 or Mobile 1 93).

 

I live just north of Atlanta, Georgia so we get 93 at the pump. I found that BP and QT seemed to show the best results for my car. There is a gas station about 20 min away with 100 unleaded which came in very handy with the turbo car(21-25psi of boost) I use to drive.

Some gas seems to be better than others, I would suggest trial and error. You can also check you mileage after each tank to see if mpg changes or not.

 

Yeah, Im all set for the trial and error. Little more to go and Ill be fueling some 92 BP. Funny thing is, there is no other BP station in a radius of 3 miles! I dont know if that indicates that BP isnt the best thing in Melbourne, Florida or not. So, ill just fuel half a tank of 92 BP and see what comes out.

As for the MPG, I wont get my hopes up. Turns out that the way I drive (according to the GPS and the Green Leaf on the Display) yields to a 9-12 MPG.