Premium fuel

[Mr1der]

anything with a higher compression be it naturally aspirated or not will need a higher octane gas to keep it a little more stable under the compression stroke.

pre detonation is a bad bad thing.

Direct Injection is a hell of a drug.

so true.

I <3 direct injection.

[MinisterofDOOM]

I'm trying to get a an explanation regarding premium fuel in the V6 engine.
My Xterra is 4.0 L, 9.7 ratio, 261 HP, 281 lb-ft T
Pathfinder: 4.0 L, 9.7 ratio, 266 HP, 288 lb-ft T

The owners manual on the Xterra says regular
The owners manual on the Pathfinder says premium.

Essentially the same engine.
Anyone shed any light on this?

Thanks

EXACTLY the same engine.
More than that, also 95% the same truck. The current Xterra and Pathfinder are very, very, very closely related.

It probably all comes down to the fact that the Xterra is marketed to offroaders and people looking for a tough truck, where the Pathy is geared toward more of a soccer mom/grocery getter/family transporter market.

In the end, if you look closely, you'll see that the Pathy only RECOMMENDS premium. Very few modern cars or trucks actually REQUIRE premium fuel. Knock sensors and modern engine management are good at adapting to fuel conditions. they have to do it anyway because gasoline octane is never exactly what's printed on the pump, and due to variations in Ethanol mixes, and due to variations in moisture content, etc.

And I'm 90% sure the KA engine was never recommended premium.
.

You'd be 90% wrong
READ YOUR MANUALS PEOPLE!!!
http://www.edmunds.com/nissan/240sx/
"From a practical standpoint, the car was hampered by a borderline-useless backseat and trunk and a need for premium fuel."

Not that I'm disputing your overall point, but I'd don't exactly consider Edmunds to be a reliable fact-checking source.

I <3 direct injection.

I want to know why the Hell the G37 doesn't have DI yet. M56 gets it (417 ft-lB!!!!!!!!!!) but not the G.

[PoorManQ45]

lies. my bike has a 12.4:1 ratio and calls for regular.

my quad has an 11.7:1 and calls for 93+.

too many factors to discuss

[MinisterofDOOM]

lies. my bike has a 12.4:1 ratio and calls for regular.

my quad has an 11.7:1 and calls for 93+.

too many factors to discuss

You really can't compare OHV and motorcycle engines and fuel requirements to those of cars. Very different worlds, with different goals and different ways of doing things.

BTW those thinking octane is related to fuel economy or performance or that the engine is smart enough to know what's burning are (in low compression machines) mistaken.

That's simply not true. Running lower-than recommended (or required especially) octane in a modern engine can lead to timing retardation, which WILL cause BOTH decreased efficiency AND performance.

In addition to that, varying conditions from those the engine was designed to work BEST under will reduce efficiency.

Then there's the fact that octane actually tends to be inversely related to energy content. Lower octane fuels actually have (very slightly) higher energy content. Which means there's yet more potential for lost power if you're running the wrong fuel.

You have to remember there's more than just FUEL to the equation. There's the way the engine was designed to work WITH the fuel.

[lamuncha]

From the '09 manual:
"FUEL RECOMMENDATION
Use 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 87 AKI (Anti-Knock Index) number (Research
octane number 91) can be used, but only under
the following precautions:
c Have the fuel tank filled only partially with
unleaded regular gasoline, and fill up with
unleaded premium as soon as possible.
c Avoid full throttle driving, and abrupt acceleration"


Seems to me it is more than just a recommendation.

[MinisterofDOOM]

Haha, I see what you mean, now...but despite the strong wording it's really still just a recommendation. It says it IS safe to use lower octanes. Look inside the fuel door; unless I'm mistaken, something like "91+ Recommended" will be printed there.

Heck, even the "Premium ONLY" section from my car's user manual comes across as just a recommendation.

Your vehicle is designed to use
“Premium” unleaded gasoline with
an (R+M)/2 octane rating of 91 or
higher for optimum performance.
The use of gasolines with lower
octane ratings may degrade performance. We do not recommend the use
of gasolines labeled as “Premium” in high altitude areas that are sold
with octane ratings of less than 91.

[lamuncha]

#@*^*!# now I have to worry about altitude!
Whoever wrote that manual definitely doesn't have much to do.

Why in the world a company would put a soccer SUV on the market that requires premium is beyond me. Nice stuff but stupid marketing. It would work just fine tuned like the Xterra.

I am on the verge of buying one but confusion reigns.

[MinisterofDOOM]

#@*^*!# now I have to worry about altitude!

Well...yes and no.

Altitude affects combustion, because air density decreases with altitude. BUT...gas stations account for that, more or less. Which is why "Premium" fuel is 91 octane up here at 4500 feet, but 93 octane near sea level. You need higher octane to compensate for knock with denser air. Either way, you're still buying "Premium" and the tradeoffs vs midgrade or regular are still the same.

Like I said before, though, the engines in these two SUVs are not just similar, they're 100% identical. If the Xterra can run on regluar, so can the Pathfinder. The HP difference is most likely due to a slight variation in exhaust design or something like that.

[Speedy7_7]

Premium is on average 20 cents more per gallon. A 20 gallon tank will cost you an extra 4 bucks. boo hoo, its really not that bad.

[Jesda]

u poor? get a huffy

[Mr1der]

really.

hell, I had to run premium in my old Supercoupe...it's honestly not that bad.

took me a while to break the habit of running 93 in my Civic but I still run mid grade just because. I need to get a premium fuel flash from Hondata...

[wingFeather]

f*** regular.

[Mr1der]

why?

in most vehicles it's the best option.

[PEZi]

because regular ain't JDM tyte y0

[themadscientist]

oh boy, you're opening Pandora's box here!

I have found a few glasses of wine and a Barry White CD to do that quite nicely.

[Oatmealman]

I was told by numerous people that premium would help my motor make more power in the jeep and when i had the motor dyno'd i only saw a few hp difference which I then made up for by upping the jet size and adding just a hint more timing and now i can run 85 all day long and still make more horsepower to the 37" tires than most people's car's make at the crank.While yes premium does make a small difference at this altitude premium fuel recommendations really are just guidelines.You can put in premium if you feel the need to but 85 is fine for most things.

Hell i ran my 99 infiniti at 19 degrees base timing on 85 for almost two years and never had a single ping,or knock.

[themadscientist]

If the motor combusts the fuel without knock, it's fine, no need to go to a higher octane. People think octane adds power, but it's the ability to run higher boost, more timing, etc that gives you the power. Running high octane in a car that runs fine on regular is a waste of money.

[Jesda]

You can run fine on regular, but your Nissan ECU will know it and kill 10% of the fun if it prefers premium.

[themadscientist]

I know what you are talking about. I sold a Skyline to a kid and I was running hi octane, it needed it. I told him if he cheaped out and bought base gas it would lose about 10-15%. A week later he called and asked "how much did you say that Japanese gas cost?"

[themadscientist]

I know what you are talking about. I sold a Skyline to a kid and I was running hi octane, it needed it. I told him if he cheaped out and bought base gas it would lose about 10-15%. A week later he called and asked "how much did you say that Japanese gas cost?"

[PoorManQ45]

wow, you guys like to waste money.

why not step up to oxygenated 112 for $7/gal. then you'll get some real results, and it's ONLY $80 more per 20 gallon tank!

if the car doesn't require it, don't waste money!

[Speedy7_7]

wow, you guys like to waste money.

why not step up to oxygenated 112 for $7/gal. then you'll get some real results, and it's ONLY $80 more per 20 gallon tank!

if the car doesn't require it, don't waste money!

But it won't gain you anything but a burned out cat if you run 112. If you run premium in a vehicle that calls for premium you will notice a change in fuel economy over running regular. That change in fuel economy might just be enough to make the 4 dollars worth it.
lets use 25 mpg as an example: 20 gallons will get you 500 miles, if you bought regular that 20 gallons cost $56.

You could run premium and get 27 mpg: 20 gallons will get you 540 miles, you paid $60.

Premium is 9 miles per dollar

Regular is 8.9 miles per dollar.

Not a huge difference, barely noticeable. But over a year it will save some money, and the car will have less problems in the future.

Putting premium in your bone stock 240 will do nothing, but newer cars are smart, they know what to do to maximize their efficiency.

Putting race fuel into anything that isn't tuned for race fuel will get you nothing, its not like it burns more powerfully, it just allows you to run higher pressure and more advanced timing without knock, if you have not tuned a car to run higher pressure and more advanced timing, the only thing that $7/gallon gets you is a nice smell and a destroyed catalytic converter.

[AZ89two4Tsx]

^ pretty sure he was joking.

[PoorManQ45]

^ pretty sure he was joking.

I was joking, and his response missed the facts too!

I said oxygenated 112. there is most certainly an increase in power!

I'm not sure why you mentioned the cats. I did not mentment leaded fuel!

[Speedy7_7]

Go ahead and put oxygenated 112 in your car and see how much horsepower you make. Good luck finding non-leaded.
better yet, by your logic, you could just throw e85 in your car and make more power without doing anything. 107 octane. very oxygenated.
Don't worry about it, I'll wait for you to search the fuel forum you are a member of before you respond to the smallest part of my post. what about the 87 to 91 argument, would you please argue based on what the op was actually talking about, or could you not find contrary information on the internet.

[PoorManQ45]

you're not bright at all.

your comment about e85 validatesmy statement.

might want to look up energy content

combustion = oxidizer + accelerant.

[Speedy7_7]

I'm sorry the sarcasm didn't carry.
You have still refused to argue why you are right about regular being just as good as premium. Or did wikipedia not have any info on that.

and what is this mathematical equation you have come up with?

Are you saying that you can increase the power of combustion with an oxidizer added to the fuel? Very good, you discovered nitrous. Now go run it in your stock car.

[seang]

SHE NEEDS PREMIUM, DUDE!!!!

[sultan]

just put diesel in your car, problem solved.

[PoorManQ45]

I'm sorry the sarcasm didn't carry.
You have still refused to argue why you are right about regular being just as good as premium. Or did wikipedia not have any info on that.

and what is this mathematical equation you have come up with?

Are you saying that you can increase the power of combustion with an oxidizer added to the fuel? Very good, you discovered nitrous. Now go run it in your stock car.

lol @ wiki...

I never made an argument for regular = premium. I stated that if premium is not required that it is a waste to use it.

I'm only using my phone to respond. I will not be typing out a full book explaining the ignorance of your statements.