# Is Premium Fuel Needed?



## Orangetang (Dec 5, 2005)

I've heard that I need to run 91 octane in my 2002 3.5L Pathfinder, period. The Fuel door says premium is recommended for optimal performance... So is 87 or 89 OK? Or does the engine actually knock/ping on lower grade fuels? What kind of long term damage can this cause, if any. 

I run 91 anyway, but 89 would hurt the wallet a little less.


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## WATSON1 (Jul 9, 2005)

Orangetang said:


> I've heard that I need to run 91 octane in my 2002 3.5L Pathfinder, period. The Fuel door says premium is recommended for optimal performance... So is 87 or 89 OK? Or does the engine actually knock/ping on lower grade fuels? What kind of long term damage can this cause, if any.
> 
> I run 91 anyway, but 89 would hurt the wallet a little less.


There's lots of discussion about this on various parts of the forum. Just saw one earlier today, just do a search for "premium". I have a Altima with the 3.5SE. Premium recommended. Nissan says the compression ratio is very high on this engine, and I found out the hard way by running mid-grade, and got some bad pinging or "spark knock".


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## Orangetang (Dec 5, 2005)

I did search for 'premium fuel' before posting, but most the thareads didn't explain what year or model vehcile they were askign about. I'm sure the engine in the 98 PF would be much different than the one in mine... 

But thanks for the tip, I'll continue to run 91 Octane.


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## Animal (Mar 25, 2005)

Orangetang said:


> I did search for 'premium fuel' before posting, but most the thareads didn't explain what year or model vehcile they were askign about. I'm sure the engine in the 98 PF would be much different than the one in mine...
> 
> But thanks for the tip, I'll continue to run 91 Octane.


You can try 89; one tank won't hurt. If it starts to knock, try not to put unnecessary load (such as hard acceleration up hill) until you add some octane boost, then go back to 91. However, if 89 runs good, do the same with 87. 
Engines have a way of being unique. For example, we just finished getting a Mustang 5.0 rebuilt and back together again (long story, but ...). It has just under 200psi compression in all cylinders and runs fine on 87, even dogging it up hill - go figure.


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## scotts03le (Jan 29, 2004)

i have been running 87 and 89 in my 03 with no knocking or pinging, however, it is noticeable rougher. On 93, it runs MUCH smoother.
So, for the extra $2.00 it costs to use 93, use 93.


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## Xeno (Oct 5, 2005)

A good balance would be to use lowest octan that does NOT cause it to knock. Anything more is a waste.

Read here for more info: http://auto.howstuffworks.com/question90.htm


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## Max96 (Aug 25, 2005)

Guys... run whatever you want in your Pathy. When running regular grade fuel, the knock sensors will detect any knocking and pinging and retard the timing accordingly. Is the lower grade gas worth it? Ehh... thats up to you. You will definitely see performance gains with the high octane stuff and you overall mileage will be a little better. During the winter I mix up the high and low octane stuff due to the cold weather and the vehicle running richer. During the summer it mostly premium. And yes, my '01 runs just fine on the regular low octane stuff. If you plan on towing a boat or any other heavy stuff, you must use the premium gas.


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## 2QIK4U (Feb 8, 2006)

I am running the 4.0 L 270 HP engine on my Pathfinder and I usually put 87 in. I haven't heard any knocking or anything. It seems to run fine, even when accelerating up a steep hill. Here in Canada the 91 stuff cost me an extra $8 per tank! I do however put the 91 or 94 in when I'm towing my 28' boat. I haven't tried towing with the 87.


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## rmd0311 (Feb 28, 2006)

Well., usually filling up with 93Oct cost me about 4 dollars more per tank... I think its definitely worth it for the better performance.


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## vdubluv74 (Feb 14, 2006)

I notice a significant gain in gas milage when i use premium gas, and like a lot of people said if its only 2 to 4 dollars more why not?


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## piste (Dec 23, 2009)

So many times I've read threads where someone will accurately explain all the technical details behind their claim that higher octane fuel is a complete waste of money UNLESS one is running a higher compression engine...don't recall what qualifies as "higher compression. What I know is my '97 SE manual recommends AT LEAST 87....which implies higher than that would serve some purpose. I also know mine has ran fine on 87 but also has slightly noticeable performance inprovement on 93.


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## Max96 (Aug 25, 2005)

fast forward 4 years... now driving an '01 325i and during the summer I only run super unleaded. There is a BIG noticeable difference in performance vs running regular in this car. Still wish I had my Pathfinder though... :balls:


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## dgangle (Nov 22, 2009)

my '01 Pathy calls for 91 but @ 165K miles it can't tell the difference. Maybe it's the lower compression due to wear??? I third the advice of those saying run the lowest grade that doesn't ping. The wifey had a '98 5.0L Exploder that called for 87 but needed 89 to quite the valve clatter. 

I question the real-world truth in people that run premium in anything that doesn't call for it or is making engine noise and say how much more performace it has. They should send me the extra $$ they are wasting on fuel as I certainly could spend it on something of actual benefit, like lottery tickets!


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## underling (Nov 26, 2006)

for the couple dollars extra for a tank of premium why mess with it. Yes the knock sensor will retard the timing, installed as a precaution against those that can't follow instruction and keep from damaging the engine. the 96-99.5 years are recommended for premium as well, and even though my pathfinder is cresting 270,000kms it still runs full synthetic front to back and premium fuel at every fill. Saving myself a couple bux at the cost of shortening the lifespan of my vehicle isn't even an option in my opinion (though I'm sure there are others that will argue in the reverse) and in the event that it doesn't, why take the chance)


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## piste (Dec 23, 2009)

Seems most every interest has their religious wars on the internets. The Octane Wars are the equivalent of Caliber Wars for firearms enthusiasts. 

As for 96-99.5 Pathys recommending premium...my 97 SE owners manual does...and doesn't. More specifically it says "use AT LEAST 87 octane". What kind of recommendation is that? Well...that implies to me that 87 is ok but higher than that is better. I ran the highest octane I could in mine for the first 6 years or so...and back then when I DID put lower octane in the tank my arse-dynomometer could indeed tell the difference. I had switched to cheaper stuff on a regular basis when gas got crazy and never went back...til now....just switching back to higher octane but splitting the difference at 89. Anyone wants to run science at me all day long telling me there's no difference is wasting their time. Hell I got a degree in chemical engineering so I might even understand some of it. As as for wasting my money....well...it is mine to waste after all isn't it. And I don't see it that way....as stated by others above....I spend what amounts to a few dollars a week in much worse ways ....every week. To each their own on this one.


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## MattyDK23 (Nov 30, 2007)

Does 87 octane gas damage our Pathys? No.

Will you see improved performance in day-to-day driving? Probably not.

Will you see improved performance in stressful situations? Yes.

I use premium when towing, driving in the mountains, and in cold Canadian winters. Through experimentation, I found that with the winter blends of gas, premium gives me a fuel economy boost significant enough to offset the added cost of it. I don't see similar gains in the summer, so I don't use it on a regular basis then.


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## quandary (Jul 6, 2007)

My 2000 has been running 87 since day 1 at the recommendation of the dealer when i bought it. At 325,000 kms, i have not had any problems aside from rust.


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## dgangle (Nov 22, 2009)

as an update on my 2001 that calls for "premium 91"....

In the last several months I have run tanks of 87 and 91 in sucession under the exact same conditions (on the same day, on the same trip, at the same continuous speed of 70MPH & conditions) and have experienced NO difference in gas milage between the 2 grades of gasoline. 

It doesn't knock, ping, have valve clatter and I can tell no seat-of-the-pants difference. Assuming 20 MPG ave in 100,000 miles at a savings of $0.40/gallon...that's $2000!!! Put 200K on your Pathy and that's $4K....a good downpayment on a new one.


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## piste (Dec 23, 2009)

dgangle said:


> as an update on my 2001 that calls for "premium 91"....
> 
> In the last several months I have run tanks of 87 and 91 in sucession under the exact same conditions (on the same day, on the same trip, at the same continuous speed of 70MPH & conditions) and have experienced NO difference in gas milage between the 2 grades of gasoline.
> 
> It doesn't knock, ping, have valve clatter and I can tell no seat-of-the-pants difference. Assuming 20 MPG ave in 100,000 miles at a savings of $0.40/gallon...that's $2000!!! Put 200K on your Pathy and that's $4K....a good downpayment on a new one.



Interesting experiment. To my thinking.... switching back and forth with each tankful is less likely a scenario where you'd notice the difference....and you may indeed never ever notice a difference. But if you are game...and have a Sunoco nearby...try 93 octane for a month and pay particular attention to "stress" conditions like hills...heavier than usual loads etc. This will allow time for the ECU and all other monitors and controls settle in with 93 octane. Then flip back to 87 and after a week or two....take particular note of performance under those "stress" conditions. That's the scenario how I notice my seat of the pants, "marginal" performance difference....note it's only marginal to me but it IS noticeable. Now as to whether or not its worth $4 grand to someone over 200K miles...that's a whole nuther matter.....


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## dgangle (Nov 22, 2009)

"This will allow time for the ECU and all other monitors and controls settle in with 93 octane".

That's laughable. As if it gets used to regular Coke then you slip it some Diet Coke. If it can tell the difference, any adjustments are made instantaneously by the ECU.


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## piste (Dec 23, 2009)

dgangle said:


> "This will allow time for the ECU and all other monitors and controls settle in with 93 octane".
> 
> That's laughable. As if it gets used to regular Coke then you slip it some Diet Coke. If it can tell the difference, any adjustments are made instantaneously by the ECU.


I guess I did not express that very well. What I was getting at was not that it would take a month for things to adjust. If you alternate each tank fill between 87 and 91...unless you ran your tank dry between each fill you end up with some degree of blend between 87 and 91 if you switch between each tank fill. Running a few tanks of the same grade will ensure you have consistency of octane throughout the system. The "month" suggestion was because the performance differences are not that dramatic IMO but are NOTICEABLE if you give it a bit of time and varying driving conditions...at least to someone who is "non-laughable" enough to perceive performance differences in their vehicle....YMMV.


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## jmrealpath (Jun 7, 2006)

Altitude does make a difference also. I live in the Denver and travel over the continental divide weekly and I run 85 mostly, because of the higher altitude. Per Wikipedia "in the Rocky Mountain (high altitude) states, 85 AKI is the minimum octane, and 91 AKI is the maximum octane available in fuel[citation needed]. The reason for this is that in higher-altitude areas, a typical naturally-aspirated engine draws in less air mass per cycle due to the reduced density of the atmosphere. This directly translates to less fuel and reduced absolute compression in the cylinder, therefore deterring knock. It is safe to fill up a carbureted car that normally takes 87 AKI fuel at sea level with 85 AKI fuel in the mountains, but at sea level the fuel may cause damage to the engine.


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## Mykroft (Nov 24, 2010)

I've never used anything but the base octane in my '02 pathfinder and I've never noticed any problems whatsoever. I even tow my 3000+ lb boat without any issues.

Tried premium once or twice, everything was the same.


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