Premium fuel

[lamuncha]

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

[PoorManQ45]

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

[troskinatior]

go regular, there was a artical about this awile ago

[corn322]

Perhaps the Pathfinder has a more aggressive ECU tune?

[lamuncha]

I guess, but with similar HP and Torque if they advanced it they sure didn't squeeze much more out to justify premium.

[VMPhil]

from everything I have read Premium is only useful on forced induction engines.

[nissangirl74]

Here is an article with some generalities about octanes.

http://www.nicoclub.com/archives/gasoli ... myths.html

I'll do some more research to see if I can find any specifics about the Pathfinder.

[PEZi]

^ that article is good for generalities

if your manual recommends premium, there is usually a reason... timing could be that reason although i agree i'd like to see bigger numbers if they advanced enough to call for premium

[PapaSmurf2k3]

Perhaps they used the greater octane for better fuel economy as opposed to HP numbers. Maybe help lessen the "sticker shock"?

[nissangirl74]

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

Do you own both? If so, which fuel are you using?

[s0m3th1ngAZ]

I was told boost and a compression ratio above 10.5 requires premium...fact or fiction?

[nissangirl74]

premium for anything running boost / supercharged; not sure about specific compression ratios

[PEZi]

I was told boost and a compression ratio above 10.5 requires premium...fact or fiction?

depends... mostly yes... 10.5 is a good number to use premium for sure

[PapaSmurf2k3]

I was told boost and a compression ratio above 10.5 requires premium...fact or fiction?

There are a LOT more factors that go into it than that. There are lots of designs/materials that dissipate heat better, prevent hot spots, etc. Saying "10.5" isn't a very good method. Hell, stock 240s have 9.5:1 compression, and require premium.

Aluminum blocks/heads dissipate heat better, so you can usually run higher compression there without the need for premium (or still run premium, and run even HIGHER compression )

Oil squirters, cooling design, altitude, ambient temperature, atomization efficiency & injection cycle (look at what direct injection can achieve) all play factors.

Really, it goes back to this:

if your manual recommends premium, there is usually a reason...

Can you run regular? In most cases, yes. Performance and fuel economy will suffer, and you could potentially damage some components/longevity if you hot dog the s*** out of it for extended periods of time on regular fuel.

[s0m3th1ngAZ]

Hell, stock 240s have 9.5:1 compression, and require premium.

What? No they dont...Texaco Regular for two years and didn't ping.

[PEZi]

What? No they dont...Texaco Regular for two years and didn't ping.

pinging isn't the only issue to be had by not running the recommended fuel as stated above

whether or not the manual says premium for the 240... dunno.. never looked at one

[Jesda]

Why put up with reduced horsepower? For a couple bucks a tank its worth it if your owners manual asks for it.

[nissangirl74]

Why put up with reduced horsepower? For a couple bucks a tank its worth it if your owners manual asks for it.

This

[BusyBadger]

^ ^ Beat me to it.

Hell, stock 240s have 9.5:1 compression, and require premium.

What? No they dont...Texaco Regular for two years and didn't ping.

No they don't...what? Have a 9.5:1 compression ratio or require premium?

whether or not the manual says premium for the 240... dunno.. never looked at one

I know the inside gas flap says premium. That being said, I've run 87 in mine for years and never had a problem and it's got just a bit over 300K on the clock on the stock mill.

[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.

[PapaSmurf2k3]

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.

[Razi]

Welp, I went turbo so premium/no premium isn't a debate anymore.
Me no want boom.

[AZ89two4Tsx]

What's the deal with a 240 being recommended premium? I NEVER put anything but regular in mine except for once during a track day. It ran no different at all. And I'm 90% sure the KA engine was never recommended premium.

Dunno about the Pathfinder/Xterra thing though. I would go to the dealer and ask one of the techs.

[PapaSmurf2k3]

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."

[PEZi]

I know the inside gas flap says premium. That being said, I've run 87 in mine for years and never had a problem and it's got just a bit over 300K on the clock on the stock mill.

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

something tells me one of these people knows more than the other.... jus' sayin'

I NEVER put anything but regular in mine except for once during a track day. It ran no different at all.

this is typical... it doesn't run better right away regardless because it takes your ECU time to realize the premium is in there

people running race gas at the track will sometimes notice that it does nothing while they're there because it hasn't adjusted to the high octane... but on the way home they might notice some extra pep.... ECU's are worthless! :

[PapaSmurf2k3]

Just sack up and twist your dizzy after putting premium or race fuel in there. You'll notice that pretty quickly.

[PEZi]

Just sack up and twist your dizzy after putting premium or race fuel in there. You'll notice that pretty quickly.

mine is fully twisted all the time....

[AZ89two4Tsx]

I know the inside gas flap says premium. That being said, I've run 87 in mine for years and never had a problem and it's got just a bit over 300K on the clock on the stock mill.

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

something tells me one of these people knows more than the other.... jus' sayin'

Mine always said "unleaded fuel only." On the inside of the gas door and and on the cluster. I assumed that meant 87.

That being said, I had a single cam. Dunno if that makes a difference.

[PEZi]

That being said, I had a single cam. Dunno if that makes a difference.

good question....

[lamuncha]

Thanks PEZi720 - probably the most likely reason. Bumped the timing up a bit to get a few more HP.

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.
The higher octane fuel is refined a bit further in the chain and different additives are use to prevent detonation.