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Re: Octane question per Pathfinder

In short, if your Pathfinder says -- I mean the actual OM states -- to

>use 91 octane, use 91...it's that simple.

Actually, it's not quite that simple. No doubt the manual will say "Use 91" but "89 is OK" like most Nissan manuals. But, there's more to it. Stick with me until the bottom line.

Here's how it works: When you accelerate, there's a chance for pre-ignition (knocking). The knock sensing mechanism is constantly checking for knock. If it detects it, it will retard the timing (in a Nissan) and stop the knocking. So, within reason, _no_ gas will cause damaging knock or engine damage.

Why do we care about octane ? Retarding the timing will reduce available power in the engine. You will have less power overall. If you are going up a hill, or pulling a trailer, or just entering a highway, you may need to press harder on the accelerator. So, gas mileage will suffer. At the upper end, you will simply have less power.

So, does it matter ? You will get slightly poorer mileage _depending_ on the exact driving conditions that week. If you are doing a lot of mountain driving, or pulling heavy loads, or just like a lot of power, you may find it somewhat diminished. Whether or not it is more economical to use Premium or Regular is very arguable.

Here's a sample calculation:

12,000 miles @ 20mpg = 600 gallons of gas used; at $1.59 for reg gas you pay $954 for gas for the year. With Premium gas at $1.65, you pay $990 for the year. That's a whopping $36 a year more for Premium. Whoopee. Even if Premium is $.20 more per gallon (and I doubt it) you still only pay an extra $120/year for Premium. And, we still haven't figured in any extra mileage due to using premium. If you get 22mpg using Premium instead of 20mpg because of the higher octane, then you only use 545 gals of gas and the Premium costs you a total cost of $900 -actually $45 *less* than regular. If you get even 1 mpg more with the Premium it costs the same as regular on a per year basis - and you get all power Nissan designed in.

Bottom line: These number are speculative. Fill in your own. The fact is that the difference in gas cost is going to be +/- $50 to $100. Now, check the price tag on that new SUV and tell me again that $100 per year really matters either way.

Bob

Reply to
'nuther Bob
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Its not that simple.

The Pathfinder owners manual ('02 Pathfinder) says: "Unleaded gasoline with an octane rating of at least 91 AKI (RON 96)" in the table of capacities and fuel/lubricants.

But then two pages later it says: "Use unleaded regular gasoline with an octane rating of at least 87 AKI (Anti-Knock Index) number (Research octane number 91). For improved vehicle performance NISSAN recommends the use of unleaded premium gasoline with an octane rating of at least AKI number 91 (Research octane number 96)."

So first you have to figure out if your local gas pump is displaying AKI or RON, then there is the double talk of "at least 87 AKI... Improved performance ... 91..."

After read> Go to the dealersip and ask to see a new Pathfinder's Owner's Manual

Reply to
E. Meyer

I don't have a Pathfinder, and I don't know anything about them, so I can only speak in generalities. So, the value of what I'm about to say is probably somewhere less than $0.02. :)

Some Nissan engines - the KA24DE is the only one I know about offhand

- require 91 octane. You can run 89 in them, and the computer will retard the timing if it detects knock. You'll take a (theoretical) performance hit, but it won't actually hurt anything.

I've never spoken with anyone who's been able to empirically measure the performance hit, which is why I'd qualify it as theoretical.

HTH

Reply to
Pronto Breakneck

I'm most concerned about hurting the engine over the long term. Premium gas here in GA is 20 to 30 cents more a gallon so we are talking $3000 over the lifetime of the vehicle

Bryan snipped-for-privacy@ohiobobcat.com

Reply to
D. Bryan Cady

If he is "considering" getting a Pathfinder, I took that to mean it'd be a 2003 or 2004 model, not a 2002. Consequently, he needs to get ahold of a 2003 or 2004 Pathfinder OM and see what IT says...which may or may not be what the 2002 manual says.

But, it's his car so he makes the call.

John D.

Reply to
John D.

Reply to
ppointer

Not really...you don't get any extra mileage using premium.

He should save his money and use what his OM states to use, no more, no less.

John D.

Reply to
John D.

Up to 2000 Pathfinder with 3.3 liter engine- Regular Gas

2001 and up Pathfinder(with the 3.5 Liter) Premium gas

BTW- Premium Gas here in Mass is 22 cents more than regular per gallon.

When I got my 1999.5 Pathpuppy- I REALLY liked getting regular for a change- as my last 2 cars(1993 Taurus SHO and 1998 Regal GS) required Premium. Unfortunately the mileage per gallon sucks!!!!!

Chris

Reply to
Jake

I don't think you followed the thread. If the engine is designed to use Premium, it stands to reason that you will get better mileage by using Premium. It's true that Premium has no real benefit for an engine designed to run on lower octane gas. I don't think that's the case in this thread.

Bob

Reply to
'nuther Bob

You need to find a better station... unless by "regular" you mean "87" octane. There should not be that kind of spread between "89" and Premium.

Bob

Reply to
'nuther Bob

Umm, I think the thread is diverting. The other poster was suggesting that he used "regular" instead of "premium". If by regular he means what you said - 87 octane - then he's really pushing the limits on that engine design.

Lets talk octanes instead :-) between 87 and premium - yeah, that sounds right. Between 89 and premium ? Sounds too steep.

But, whatever. 12000 miles @ 25mpg and that .20/gal will cost you an extra whopping $96/year. Whop-te-do.

Bob

Reply to
'nuther Bob

ok bOB- I want A "better" brake job- I will do it myself.

But What is a "better" gas station! Station list regular as 87, economy as 86 or 85, Plus as 89, and premium as 91.

Regular is 20 to 22 cents less than premium, and plus is about 10 cents less.

Reply to
Jake

The owners manual for my '02 Pathfinder very clearly says 87. It then goes on to say you will get improved performance from 91. Doesn't sound like its "pushing the limits of engine design" to me.

I have run an occasional tank of 87 and occasionally 89 in the Pathfinder and there is no difference in mileage. I have not pushed it on the highway to see if there is any obvious difference in performance. In city and combination driving I can't feel any difference.

Reply to
E. Meyer

That is weird. When test driving an 01' Pathfinder, I read the manuel and it say 91 octane. I wonder if they changed their mind in recent years

Bryan

Reply to
D. Bryan Cady

Its really pretty confusing - If you look on the spec page it says 91, but then two pages later it says 87, but they recommend 91 for improved performance.

My guess is the eng> >

Reply to
E. Meyer

It's not confusing at all unless you take it out of context or out of order.

First there's the capacities/rec fuel chart. It says "91". Immediately following that you should find the "Fuel Recommendation" paragraph:

"FUEL RECOMMENDATION Unleaded Premium gasoline with an octane rating of at least 91 AKI. If unleaded premium gasoline is NOT AVAILABLE, unleaded regular gasoline with an octane rating of at least 87AKI can be used. However, for MAXIMUM VEHICLE PERFORMANCE, the use of unleaded PREMIUM GASOLINE is recommended". (emphasis added)

Later in the manual you will find "Octane Rating Tips". In this section they will discuss octane rating *in reference* to the earlier section on recommended gasolines. This section includes information on high altitude differences. It does *not negate* the earlier paragraph, it *supplements* it.

Bob

Reply to
'nuther Bob

So basically...you can use 87 AKI all you want through the life of the SUV as long you don't mind a hit in performance. (Without hurting the engine.) That is what I take away from this.

Bryan

Reply to
D. Bryan Cady

Reply to
E. Meyer

Reply to
E. Meyer

I found about 4-5 mpg difference between the two, and that's the case with my new Murano as well.

Stick with high octane. It doesn't cost more once you consider the increased mpg.

Wes

Reply to
Wes

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