hey guys,
So i took people's advice and tried higher octane for my car. The reason i never did this before was neither of my parents put in anything other than regular, and when the car became mine, i didn't start using higher octane because i was planning on getting a new maxima real soon. But i finally got curious and put in 94 octane at the sunoco by my house, and i really noticed a difference.
When i had used a stop watch ( i know it's not very accurate) to time my
0-60mph's i had always got 9.1 seconds. (97 gxe auto 200+ km's) But after getting the higher octane, i got 8.1, 8.5, 8.7. they were all on different road's so i think that might be the difference. I know this is not the most accurate test, but it might convince other people who are not getting full potential out of their car's, to pay the extra few cents and do your car a favor.

 

Yea, IMO, its always worth it to pay a little extra for the higher octane. I started doing that too.

 

yea your car runs alot smoother!

 

I noticed when I bought my car, there was a bit of lag when the power would come on. After 2 tanks of 93 octane its responding instantly. Much improved.

 

Hmm...either this is really funny, or I don't know jack about gasoline.

 

if u do the math, it only costs like a dollar more to put the higher octane in it.

 

Same here... just started filling 93 octane, and I feel a very big difference!!!

 

You actually don't pay much more at all. Although the lower octane gas is cheaper you will get worse gas mileage. You'll end up putting more of the cheaper stuff in to go the same distance, hence reducing your 'savings'. You're better off using the good stuff and have your car running it's best.

There is also the opposite out there. My Grand Cherokee is recommended to run 87. I was putting high octane in until I really took the time to understand why I shouldn't. Now that I know and always run 87 in the Jeep, it runs a lot better than it did on premium. Most people wouldn't think 'better' gas would cause a car to run worse. The different grades of gas are there for specific reasons and it's best to follow manufactures recommendations.

Sorry, I'll shut up now.

 

I think it is funny too.
I don't feel any performance difference with 93 octane than with 87. In fact, the manual for our cars says that if you don't have access to 91 octane, just use 87 and it will be fine. Every once in a while, I will run 93 octane through there, but not very often.

Plus, gas mileage is the same either way. In fact, you will probably get worse gas mileage with higher octane, because you will be thinking it is performing better and getting on the gas more.

 

i have been getting horrible gas mileage recently and i jumped down to PLUS and OMG there is such a big difference in power when u get cheap wit the gas. its the nutrients our car needs, drug the car up on that good ****

 

Yeah I still think it's cheaper to run higher octane then low. First it's only a dollar more. Second of all better perfomance. Third of all you are risking your KS and O2 sensors to go out prematurely.

 

you guys like high octane? ehh? get a gallon or toulene and mix that in with your tank, then you'll see a spike in octane if you use 93 and one gallong you will get about 96, there is a sticky in the boosted forum for those who have not yet read it

 

id like to defend the fact that higher octane does help, because one time unknowingly they filled up 87 octane in my car, and i kept whining about why my car was feeling a little more sluggish, anyway i was checking how much i just spent on $15 worth of gas, and to my surprise it was 87 octane, i filled up the remainder with 93 and tried to balance it out, and eventually i twas a little smoother, but the next fillup was definately alot of difference, thers difference in the additives, i think they all have a baseline, and its upto them to put in wahteer they want after, motorvate has an article about the differences in sunoco and the other gases. its pretty interesting for those who have not read it

 

I will defend again also. Everyone wants to replace their knock sensor but must not know all of what it does. Lower octane gas combusts at a lower temperature. Our engines run hotter than some and therefore the lower octane gas can preignite - "knock". The knock sensor then retards spark instead of advancing it to save our engine. When the timing is retarded we lose horsepower, performance. When a knock sensor isn't working our timing isn't getting advanced and there is lack of horsepower, performance.

As I mentioned in my earlier post about my Grand Cherokee, that engine should run on 87. That engine runs cooler. If I use premium, not all of the fuel will combust since the higher octane requires higher temperatures to fully vaporize.

 

you have a valid point about the G. Cherokee...but why would our stock manuals say that it is perfectly all right to run 87 in them if it wasn't?

 

They're saying it won't hurt to run it since the car is designed to detect knock and adjust timing, however higher octane is recommended for best performance. Here the section right from our manuals. They aren't recommending higher octane to make the oil companies richer, they recommend it for the reasons I stated above.

FUEL RECOMMENDATION
Unleaded premium gasoline with an octane
rating of at least 91 AKI (Anti-Knock Index)
number (Research octane number 96)
If unleaded premium gasoline is not available,
unleaded regular gasoline with an
octane rating of at least 87 AKI (Research
octane number 91) can be used.
However, for maximum vehicle performance,
the use of unleaded premium gasoline
is recommended.

 

I know what it reads like, but how much of a difference can using the premium really make? I mean, people say their car is sluggish, but how sluggish can it really be. I am curious.

 

try it and kill your knock sensor in the process

no, seriously.. it does make a difference. more pure gas.

 

okay, well, how much of a difference. Give me something to go by here. I mean, are we talking 1 hp difference............are we talking .4 sec on the 1/4 mile? What?

And, according to the ones that say premium is the way to go, I have probably already killed my knock sensor. What do you recommend, replace it and start using at least 91 octane?

 

Yes, replace it and use the octane that's recommended. I took a look at your home page. This obviously isn't your junk daily driver. Fix the inherent engine component that's broken before you do any more 'modding'. Why so skeptical? This isn't Marvel mystery oil or some other additive. This is valid technology. Just because you hear about the detergents they put in 'premium' to make your car run 'soooo' much better don't let that lead you to believe that that's what higher octane is. The explanation I gave earlier is just physics and not marketing garbage.

 

When my dad got the car, he would only put 87 octane in the car and the car lagged a lot. When I would stop completely and go, the car wouldn't move for a second. It was like the car was in neutral for a second and then it kicked into drive.

When he gave me the car, I looked at the manual and it said to use premium so I tried it for a few weeks and the car would actually go as soon as I pressed the gas.

If I'm spending $27 to put in regular fuel, I might as well get the good stuff for $30 I got 1-2 MPG more with premium so I'm probably paying about a dollar extra a tank to go the same amount of miles for the premium fuel.

 

I am a beliver too. . .


I was reading, this threat, and more, I was low on gas, and I dropped $10 of the good stuff in there . . . MAN!!

She just moved so gracefully, Changing gears felt lighter, the idle was a lot smoother, I had no idea I would feel such a difference, I though it would treat the engine well but I wouldn't really feel it, but DAMN!


Premium all the way, plus mathematically it does cost that much more.


Peace

 

hmm

why is it that I get 370 miles a tank with 91 octane, but with 89 octane I get 400+ miles ?

 

dang.. im happy if i can get over 300 miles per tank

 

I WANT PCP FOR MY CAR!!! LOL

 

Ok...well either I am grossly misinformed, or this thread is too funny.

Gasoline can combust when put under pressure. Low octane fuel requires less pressure to combust.

The reason we need high octane is because our engine has a fairly high compression ratio. If you run low octane gas, you run the risk of it combusting on the compression stroke...this is predetonation, and is very bad for an engine.

As far as I know, as long as you don't suffer predetonation, you should see no change in performance.

 

It's the high temperature during compression. It's not just the compression. Your right about no predetonation, no performance loss, as long as your knock sensor is working and your not getting predetonation. Since our cars adjust for it, you will see a loss of performance telling you the car is adjusting, retarding timing, to prevent predetonation.

 

techie, I already knew that about the predetonation and stuff. My older brother is a car freak, and when I actually listen to him sometimes, I learn stuff.(I wish I knew as much about cars as him). Also, I don't know why I am skeptical. Probably mostly because of having to drop a lot more money into it. I mean, I already do that with oil and stuff. Mobile 1 syn is not cheap... ha ha. It is not because of the detergents or anything.

Sryth, what are you saying.........use 91 or not? I agree with you(from everything I have learned about engines) that is is very bad for the gasoline to predetonate in the engine. From my understanding, it is not supposed to combust until the top of the compression stroke(after compressed). So, what are you recommending?

 

I'm recommending what Nissan recommends...premium fuel only. Not for performance, but to prevent predetonation.

I personally use the highest grade at the pump...91 around here.

 

We have 93 here. Necessary or not? I mean, I could use 91, but 93 is not much more.

 

the only bad thing about 91 over 93 is that more people use 93 octane rather than 91. Not sure of your climate but in the Northeast and the rest of the snowbelt there is a huge problem of water in gas. It generally stems from how long gas sits and the weather. In the summer it's not a huge problem but in the winter, spring and fall it's a big problem. I would recommend 93 for that reason...beyond the hp gains

 

I wonder if this is true. Anyone have any statistical data of gasoline usage?

I'd bet most people use the 87 stuff, as most cars are designed for it. It stands to reason that you are right, though. Most people who would put premium in, would probably go for the 93 octane because it's "better".

 

91-93 octane fuel is recommended by Nissan. When you have this fuel in your tank, the ECU will run maximum performance settings and you'll get full potential out of the engine.


With 87 octane fuel, the engine will start knocking because the octane level is not sufficient for the compression ratio and state of tune of the engine. The knock sensor will detect this and retard the ignition timing. This will cause you to lose power and responsiveness and now you're getting less power per unit of fuel. Your butt-dyno will notice this and respond by opening the throttle more. Now you're burning more fuel for a given level of acceleration and your mileage goes down.


The difference? I believe Warren (Veetec) may have "accidentally" dynoed his car on 87. He said he put 91/93 in it but the car just didn't feel right and when he dynoed the car is was low. They may have switched accidentally at the station. He burned through that tank, refilled with premium at another station and redynoed. +5 fwhp and +8 fwtq, or about 6hp and 10tq at the crank.

 

It's a japanese car. It can run on high or low octane. Higher means your spark might be quicker or more efficient depending on all types of conditions but you should get about the same amount of mileage per gallon.

Your tires, road conditions, and driving habits are going to affect your mileage more than your gas octane rating if your engine is up to specs.

In the end if you buy high octane gas your more likely to force gas prices to go up. If you buy the low octane the prices will more likely stabilize. Think about it. The only difference is there is gas has been oxygenated it still has all the sulphur content as low octane so it isn't any cleaner. You will be able to go faster or have smother quick starts, but your mileage is not likely to change.

I used to go cross country all the time and I would get about 487 miles per tank sometimes getting 30 miles to the gallon on 87 octane the only thing I notice with running 91 or higher is that it appears I get better power at take off or going up mountains(alot less knock) the gas mileage doesn't change.

 

So can any car. But it'll run better (or worse) depending on what kind of gas you put in it because every engine is tuned with a specific octane level in mind.

Higher octane fuel lets the ECU run more advanced timing and therefore more power. The "spark" is the same, it all depends on when it fires. And your mileage is more likely to go down with lower octane, but it all depends on driving conditions and your style of driving.

When people's knock sensors go out and the timing advance goes to rock bottom, mileage can drop by as much as 5 or even 10 mpg. Just running 87 octane will be more mild, but most people will still probably see a drop of mileage.

I have. And this makes no sense.

I wasn't aware that buying regular vs premium fuel had an effect on International oil prices.

Again, it all depends on the driving style. It's more than just "smoother starts"

Here's that dyno I mentioned. More power over the entire rev range.



Straight highway driving is different because at cruise, cylinder pressures are never high and the ECU can still run full timing advance even on the lower octane fuel. Urban cut and thrust is the exact opposite. On regular your mileage will probably be horrendous but much better on premium. And you should never hear any knocking if your knock sensor is working properly. That's what it's there for. If you're actually hearing knock, you have other problems (possible coil issues).

 

It's impressive that you have a graph that shows about a 2 hp boost. You will get a knock when the car is under heavy load going up a mountain such as the Rockys. This is with all cars. Your dealing with fewer oxygen molecules in the air.

You have seen gas prices go up while the price for a barrel of oil goes down. If you been living since 1980 when gas shot up to 1.43 (which is about 2.83 in todays dollars) a variety of factors push up the price. Just last year or two years ago before the second gulf war, there wasn't a shortage there wasn't anything but an adequate supply and gas prices went up to 1.78 national average for 87 octane.

Economics law of supply and demand. Diesel used to be a bargain and now you have a lot more diesel engines being used than 30 years ago. My guess is you can get a diesel engine in your maxima in japan.

Like I said and I believe you agreed with me that tire pressure, road conditions, and driving habits are going to affect your gas mileage than your octane rating. Your top speed, altitude, and accelleration from stop is where your high octane rating would come into play.

Some places sold bluefuel or 96 octane (usually around where people race modified cars) and if you run this constantly your probably going to damage your emmision controls to include your catalytic converter more than running 87 octane.

 

If you want to ignore the facts, that's fine. But 10 lb-ft of torque at the crank through most of the rev range is significant.

Nope, not with all cars. Again, on modern cars with knock control you should never hear any knocking. You'll may notice a decrease in performance or mileage but that's it. If you drive a car that's not equipped with a knock sensor then yes, in extreme conditions you might hear some knocking. BTW high altitude decreases an engine's demand for octane.

Since you're not talking about how buying 87 octane will "stabilize" fuel prices but buying premium will cause them to go up, I'll just assume that you're withdrawing that statement then?

You attempt to confuse the argument by introducing more variables. In my driving conditions (lots of urban cut and thrust and hard acceleration) my mileage would drop considerably on lower octane fuel @ sea level.

Once you reach the required octane level where an engine can run at its maximum performance settings, adding even more octane will only hurt you, not help you.

 

Lot's of issues here let me see if I can remember them all.

Your saying if you live in Denver you shouldn't need the high octane? And if you live in LA you do? It would still be two different formulations even if it is 87 or 92 octane.

Quickly with the high octane and gas prices. So many new cars want you to use high octane gas even if it isn't absolutely necessary this drives up the demand for 92 which in turn drives up prices because 92 is more expensive than 87 with the additives. This doesn't mean you will be buying 92 because you just might as well be buying 87 and not knowing it. They check the amount of gas going to the tank more than they check the octane.

If everyone bought 87 what would happen to 92? They would still be making 92 and would have an over abundant supply of 92, so gas prices would fall eventhough 87 demand has increased because there is already an abundance of 87.

You stated 10 pounds of torque and yes like I said this would help when you are pulling a load especially up a mountain.

Your engine doesn't need the 92 octane at high altitudes is partially true. If your car will be running at top speed or to get a higher top speed at high altitude then you will need higher octane. Don't believe me just ask the japanese zero pilots in wwII running needled 87 octane (this was all they could get before the embargo) compared to americans running 92.

Your still going to get the same gas mileage/range.

If your getting lower mileage at sea level it's due to your driving, tires, and the condition of the road.

Right now I am about 30 feet above sea level or less. I get 27 mpg running 87 octane this is urban area, my average speed is around 42 mph, I was getting better mileage but I went with 16 inch tires/rims.

If I go 55 or 60 mph constant I get 29 mpg and would have to refuel at about 448 miles.

So, your not going to convence me that 92 is going to get me better anything. I have 220,000 miles on the 95 max and I have 223,000 mile on my 4x4 87 pathfinder.

Now if my tire pressure fall a pound or two my overall gas mileage will drop an average of 1 mile or 2 per gallon.

Now if your running ethanol it's a completely different story. That would make your arguement correct. Ethanol doesn't burn efficient and the drop is about 20 percent.

 

Regardless of formulation, the octane level present in the fuel is what needs attention and you want just enough so that the engine can run at full performance.

A nice paper argument, but I don't think it holds much water. Oil prices are still set by global supply and international politics. If there is relatively more demand for premium vs regular then refineries will churn out more premium and less regular. Overall demand still remains the same, and as you said, people pay more attention to number of gallons, and you can get regular or premium from the same barrel of crude oil.

Or accelerating hard from a dead stop.
Or pulling away from a light.
Or rounding a corner and getting on it hard in 2nd gear.
Or with a 3rd gear pass on the highway.
Or trying to get max performance for a 1/4 mile run.
Or pulling away from a corner on the autocross.

You still get much better performance on premium fuel, because that's specifically what the engine was designed to run on.

Can we PLEASE try to compare apples to apples here!

Straight from the owner's manual of my 1999 Maxima.

FUEL RECOMMENDATION: Unleaded premium gasoline with an octane rating of at least 91. If unleaded premium gasoline is not available, unleaded regular gasoline with an octane rating of at least 87 can be used. However, for maximum vehicle performance, the use of unleaded premium gasoline is recommended.

Octane Rating Tips: In most parts of North America, you should use unleaded gasoline with an octane rating of at least 91. However, you may use unleaded gasoline with an octane rating as low as 85 in these high altitude areas [over 4,000 ft] such as: Colorado, Montana, New Mexico, Utah, Wyoming, northeastern Nevada, southern Idaho, western South Dakota, western Nebraska, and that part of Texas which is directly south of New Mexico.

If you're at high-altitude, it doesn't matter what sort of load or "top-speed" you're trying to achieve in an automobile. The lower air density and resulting air pressure will mean that the pressures inside the cylinder will never be high enough even at full throttle to warrant the higher octane fuel. Therefore, even Nissan states that you don't need the higher octane fuel at higher altitudes.

As for World War II Fighters, you know a lot of them used superchargers, right? Heck, some of them even had twin-stage superchargers. No boost at low-altitude since there was plenty of air pressure, boost on but lower levels of it at medium altitudes, and finally higher boost at high altitudes to compensate for the lack of air pressure. And since they were warbirds, you can bet the engines ran pretty aggressive compression ratios and aggressive ignition timing and fuel settings also. So of course they probably wanted higher octane fuel. The lack of a little power in an warbird could mean the loss of a pilot, plane, and maybe even a battle.

Nope, you're flat out wrong and I've tested it.

I normally average about 23 mpg in my urban cut-n-thrust driving on 93 octane. Once my parents were in town and they borrowed my car. My father noticed I was low on gas so he took the liberty of filling it up with 87 for me. My mileage dropped to 20 mpg in the same driving and same everything else. I asked him what he put in it and he said 87 (they drive 4-cylinder Camry's ) The engine was knocking, the knock sensor detected it, rolled back the timing, engine responsiveness and power decreased, and my right foot compensated for it by opening the throttle more, thus getting poorer fuel mileage. And when my knock sensor went out, it retards the timing even more. I never got a full tank on it (I bypassed it), but others here report mileage in the teens with blown knock sensors. It's no coincidence that ignition timing has a direct correlation with engine power and fuel mileage. It's just how they work.

That's fine. No matter how much evidence you present some people will never believe you. But some of what you say just isn't technically correct, nor even relevant to the argument. Maybe in your driving and conditions you, on average, never get on it enough to warrant using higher octane fuels. And it sounds like you do a lot of highway driving where throttle position is always low. If so, you very well may get better mileage on 87. But for the cars in general, and for most people here (who like driving their cars relatively harder than most), what you say will not hold true.

Edit: Oh BTW, our Toyota Highlander (10.5:1 compression, even higher than the Maxima) says only 87 is "required" but to use premium for "best performance". It most definitely has some added pep (10-15 lb-ft on the butt-dyno I'd say) on premium fuel, and it also gets better mileage with it also. Again, primarily urban cut-n-thrust style driving.

 

So you're saying that you will definitely get a knock if you run 87? This is the first I've heard that claim.

Ok...so he may have run the 1st dyno on 87. Were these dynos on different days? Were the graphs corrected?