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There's been a bit of a debate about which grade of fuel you should burn. Some people tell me that I should burn high octane fuel, as it's better for the engine. They claim it reduces injector build-up, keeps the engine running clean and reduces emissions. On the other hand, some have told me to burn 87 octane, as anything above that is a waste of money. I've even heard that too high octane will leave carbon deposits in the engine, cause excessive wear, and be slower to heat up (which can be a problem here in frigid Indiana!). I've also heard that knocking or pinging can be attributed to low octane fuel usage.

Any thoughts on this? What fuel do YOU burn in your Armada?

Thanks!

Drew
 

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Well its not an Armada but its still the same engine. I have a Titan and I posted this over on Clubtitan.org . I was always saying that I could not tell the difference between the 87 oct and the 93 oct fuel. So after the first 2 tanks of 93 I switched to 87. I have been running it for about 3 1/2 months now. Well about 2 weeks ago I decided to get some 93 because it was on sale same price as the 87. Well let me tell you after just a little bit i really started to notice a change. It felt a bit peppier and smoother. I know what your thinking you don't believe me but I tell you I can feel the difference. As far as I'm concerned I will keep getting the midgrade or the 93. Just my 2 cents.
M4ck
 

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m4ck said:
Well its not an Armada but its still the same engine. I have a Titan and I posted this over on Clubtitan.org . I was always saying that I could not tell the difference between the 87 oct and the 93 oct fuel. So after the first 2 tanks of 93 I switched to 87. I have been running it for about 3 1/2 months now. Well about 2 weeks ago I decided to get some 93 because it was on sale same price as the 87. Well let me tell you after just a little bit i really started to notice a change. It felt a bit peppier and smoother. I know what your thinking you don't believe me but I tell you I can feel the difference. As far as I'm concerned I will keep getting the midgrade or the 93. Just my 2 cents.
M4ck

This is a good question/thread, because I'm curious about this as well. I have put 93 in my Armada every fill up but one, where I put 89 in. Everything I've read, including the manual, says the engine was designed (and performance specs measured) running 87. With that in mind, you should be able to run 87, and have no loss of power or anything. However, what I really want to know is, would I gain power if I had my computer reprogrammed for 93, or is the Nissan processor self adjusting??
 

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I'm no wiz or anything but I believe just about all vehicles in the last 10 yrs or so are able to adjust automatically.
M4ck
 

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m4ck said:
I'm no wiz or anything but I believe just about all vehicles in the last 10 yrs or so are able to adjust automatically.
M4ck
I'm a little confused about this -- because I've read of people specifically reprogramming for 93 octane -- we need to get some Nissan Techs in here.
 

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The computer in your Armada (or any other recent year model vehicle) automatically adjusts over time to run optimally on whatever grade of gasoline that you put in. If you are running 87 octane (as I am), don't expect to dump in a tankful of 93 octane and see a huge difference in performance because you wont. If you run several tanks of 93 you may see a bit better gas mileage but with todays gasoline prices, the benefit hardly outweighs the price at the pump.
 

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The owner's manual for my Maxima says to run higher octane fuel for optimum performance. I have always run the highest grade, and have had no issues. The manual for the Armada says that 87 octane is sufficient. I'm not an expert, but my guess is that the computer will adapt, but if the default is 87, putting 91 or 93 in it won't make any difference. If the default is 91, then running 87 will decrease performance and mileage.

Also, note that the Infiniti version of the Armada requires 91 octane. Does it use a different computer program? Can that program be applied to the Armada for an additional 10 hp, or are there other changes that get the 10 hp?

Keith
 

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Echoing and amplifying some of what has already been said...

The computer primarily adjusts timing to keep the engine from knocking ... which is primarily a function of octane. On an older pre-computer motor, your timing is mechanically controlled, so you set it based on the type of fuel and conditions in which you were running. You can safely put any type of pump gas in your Armada and the engine will automatically adjust for the fuel, driving conditions, altitude, etc.

That said, because you can dial in a little more advance with a higher octane fuel, you should get better performance running the premium fuel...might be a consideration if you are doing towing. On my non-turbo Volvo, I run premium, because losing any of the 162hp really impacts performance. For the Armada, where you already have more than enough power, the price difference and the Armada's mid-teen's gas mileage should make regular unleaded your usual choice.

In regard to the Infiniti 91 octane recommendation, it's tuned to provide another 10hp and 5 ft-lbs of torque. It could be that these figures are only reached running the higher octane fuel, but again, the computer allows the motor to still run fine on 87 octane. But if you're paying the extra $$$ for the QX, maybe the additional coin at the pump doesn't make a difference to you.

Pardon the long post.

Matt
 

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When I picked up our Armada, the dealer I got it from specifically told us to use 87 octane. I found this weird for such a powerful engine. Since the truck came with a full tank, it gave me a few hours, LOL, to check the manual before we needed to fill up again. Sure enough, the manual says 87. So, that is what it gets. I tried 93 and found that the gas mileage decreased. With 87, I consistently get 12-13mpg city. With the 93, it went to 10! I drove normally during the period as the truck was new. Now with 2000 miles on it, we are still using 87 and mileage is bearable for a truck of its size and power. All and all, I love this truck!
 

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Discussion Starter #10
OK well I checked my mileage in-town, and it was 12 mpg. Yesterday I drove to Chicago Midway Airport - about 200 miles each way - and got 13.6 on the highway. This is with 94 octane fuel. Believe it or not - my 2003 Pathfinder rarely got above 20 mpg. It's V6 was extremely powerful, and a real guzzler, so the upgrade to Armada isn't much more of a fuel expense.

Armada is definately not going to be out in a hybrid anytime soon! :p
 

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O.K. - So I'm Cheap

I'm running the low octane (down to 85) from the pumps and have had no pinging. After 4 months, my MPG is averaging right at 14.0. As noted by others, the power of this truck is plenty for me as is.

Bill
 

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OCTANE - 87 or 91 or 93?

Okay, I used to rebuild and "blue print" VW water cooled engines. So I think this applies the Nissan engines as well.
Most every engine built recently has the ability to advance or retard ignition timing to adjust to the octane rating you put in. (To a certain degree)
You can definitely feel the difference if you are towing or just flooring the gas pedal. With higher octane fuel like 91 or 93, your engine will advance the timing giving you more HP. With a big engine like the Armada/Titan 5.6L, this should be as much as a new CAI or low flow exhaust.

Bottom line, save your money and get 87. If you are towing or just like to blow away Honda Accords and Nissan Altima's away off the line, get 91 or 93.

I figure it's a cheap performance mod.
 

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Yes

andy said:
Okay, I used to rebuild and "blue print" VW water cooled engines. So I think this applies the Nissan engines as well.
Most every engine built recently has the ability to advance or retard ignition timing to adjust to the octane rating you put in. (To a certain degree)
You can definitely feel the difference if you are towing or just flooring the gas pedal. With higher octane fuel like 91 or 93, your engine will advance the timing giving you more HP. With a big engine like the Armada/Titan 5.6L, this should be as much as a new CAI or low flow exhaust.

Bottom line, save your money and get 87. If you are towing or just like to blow away Honda Accords and Nissan Altima's away off the line, get 91 or 93.

I figure it's a cheap performance mod.
I think you have it right Andy, I only use premium when towing, and for sure when towing in hot weather(more likely to ping). The engine management computer will advance timing until knock, if you have better fuel you will get more advance hence more power. But if you are not using the extra power (towing...), your money is pretty much wasted.
 

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Resetting Computer(ECU)

If any of you guys want to test these theories, the easiest way to get the computer to reset is by disconnecting the negative from the battery. After you do that pump the brakes several times to make sure everything is cleared out. Then put your 93 in, run about 2-3 tanks and you should have an average of about what your mpg should be. Then reset the ECU again and try it with 87. If anyone tries this, let me know what you find out.
 

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I've been using just 87 octane and i'm getting around 16mpg. Consistantly. I'm on my 4 tank of gas now. I've been gunning it lately and i'm still getting around 16mpg. Putting in 93 is just a waste of money for our cars.
 

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16MPG? Are you perpetually going down hill? I can't seem to get over 12mpg unless I'm on the freeway for couple hundred miles straight. Then I can get 18mpg.
 

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Kind of interesting, I guess...??
Yesterday, I loaded up back of Armada with 40 boxes of Pergo at 35lbs per box. = 1,400 lbs of cargo plus my 225lbs. I drove 120 miles stop and go traffic and still got the same 12mpg. Maybe the torquey engine loves to pull a lot of weight with no sweat.
 

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There are several excellent discussions of octane and our ECU's over on the Titantalk forum. They are technical and involve some pretty sophisticated engine analysis tools which have done real time timing advance measurements with different octane fuels under different load conditions.

I'll try to summarize and also supply some "back channel" input from an anonymous Endurance engine engineer at Nissan.

1. The engineer confirms what we have suspected. The ECU's and engines are identical on the production lines for the Armada and the Q56. We have the same stuff.

2. Our ECU's are of the new generation, smart "learning" ECU's that take data from the knock sensor and a lot of other inputs and will continue to advance timing until knock is detected, and retard it when driving conditions tell the computer to do so.

3. That means that it takes the computer a little time, perhaps hours, maybe days to adjust to different driving habits. Aggressive driving will teach the computer that you want full timing advance more quickly under WOT (wide open throttle) conditions. So changes in fuel can produce some unusual results. A change to premium might take a little time for any benefit to take place. Once the computer is used to running premium, a sudden change back to regular could result in a little loss of power until the computer readjusts.

4. This is what we believe happens: The premium fuel will, indeed, permit the timing to advance an additional 10 degrees or so, but only under full WOT situations. Once the computer recognizes the change and learns to permit the timing to advance more, it does, indeed produce about 10 more bhp and about 10 more pounds of torque. And as long as 93 octane or higher is fed to the engine, the computer will permit this advance at WOT on demand.

This means that the Armada and QX56 engines are identical and each will produce the power rating of the other when using the other's fuel, once the ECU adjusts.

5. The good news or bad news, depending on how you look at it is that 10 bhp and 10 pounds of torque is real, but cannot really be measured by the seat of the pants and adds very little to performance. It will show up on a chassis dyno or a good accelerometer. I can demonstrate that small gain on an accelerometer.

But, this is only under WOT conditions, and even then only when we push the engine up high into the power band. These are conditions most of us rarely use. But the fuel is much more expensive and is being burned all the time, not just when you are at WOT at or near redline.

In terms of performance, the net result will be less than one tenth of a second gain in the quarter mile. This might mean a ten foot difference over the 1320 feet distance, at best. It will not improve gas mileage, and might actually decrease it slightly, especially if you are getting into the right pedal more frequently because of the desire to want to "feel" this extra slight power, which you really can't feel.

6. With respect to the QX56 owners here, I suggest that some prestige car or truck owners are lured to the extra horsepower claim and the belief that if the car or truck is "premium" then the fuel should be also. I would suggest that they try their trucks with 87 octane and save the money. The QX56 is a beautiful truck, and nobody knows what is in the tank.

7. For us Armada owners, if you are going to tow a heavy trailer, the little extra oomph and timing advance may be a benefit, especially if you tow on steep grades. Or if you want to take your truck to the strip or engage in some other operation where maximum WOT performance is desired, you get a little gain. For the rest us, do like me and run 87 octane unless you have one of the above reasons. At twenty cents per gallon price difference (or greater) the difference adds up soon.

BTW, I get 11 mpg around town and 14 on the highway with the Big Tow package and the extra weight of the 4x4 front axle and transfer case. Running premium did not seem to change those numbers appreciably.

Just my admittedly wordy two cents worth.
 

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Gas Mileage - not a strong point, but OK

I am at about 8200 miles on my 04 LE 2WD with Big Tow package. Have been getting 12 MPG (and less, depending on how many Accords I need to see in my rear view :rolleyes: ).

Highway mileage is 17 constant, whether or not my pop-up tent trailer (2500 lb and low profile) is attached. Decline in acceleration and braking effectiveness with the trailer behind me are minor but noticeable. Went up about 3 miles of 7% grade last weekend and noticed the trans cooler indication going up some. Slacked off when I actually got my foot in it, pushing to a lower gear w/more RPMs. :)

I have never put anything but 87 in it (even a few fillups in Mexico over spring break) and I'm not wanting for power. My brother has an Xterra and doesn't even get up to 16 MPG on long trips. Really gets his goat: :censor:

Fred
 

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No more, please!

I really hate to say this but I gotta, THIS SUBJECT HAS BEEN BEAT TO DEATH! There are at least 3 other threads with a zillion replies that pertain to the exact same subject, do a search and maybe read the owners manual.
 
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