Titan Octane Requirements

curdog · Apr 18, 2006

In my community, reguar gas is 85.5 octane. My dealer advised me to run regular gas, claiming there is no need for middle grade or premium. My first tank was 85.5 and it ran fine, no pinging, no knocks. My owner's manual suggests 87 octane. Middle grade in my area is 88 octane and this is what I have been using but at a $.10 per gallon additional cost.
Any comments or opinions on what I should run....or what you use?

mtofell · Apr 18, 2006

There were a couple threads within the last couple weeks with A TON of info, opinions, etc. about HP and higher octane gas. As for the minimum requirements, I thought I read in the manual that 87 was the minimum. I didn't realize there was anything lower than 87 out there.

sudden urge · Apr 18, 2006

There isn't anything under 87 that I have seen.

4X4SoCalTitan · Apr 18, 2006

Hello. May I ask where you are from?

curdog said:
In my community, reguar gas is 85.5 octane. My dealer advised me to run regular gas, claiming there is no need for middle grade or premium. My first tank was 85.5 and it ran fine, no pinging, no knocks. My owner's manual suggests 87 octane. Middle grade in my area is 88 octane and this is what I have been using but at a $.10 per gallon additional cost.
Any comments or opinions on what I should run....or what you use?

pi3yeargrad · Apr 18, 2006

curdog said:
In my community, reguar gas is 85.5 octane. My dealer advised me to run regular gas, claiming there is no need for middle grade or premium. My first tank was 85.5 and it ran fine, no pinging, no knocks. My owner's manual suggests 87 octane. Middle grade in my area is 88 octane and this is what I have been using but at a $.10 per gallon additional cost.
Any comments or opinions on what I should run....or what you use?

what the hecks .10 a gallon? a whole 2.40 a tank full???

...lol...u guys crack me up...

EDIT: oh yeah I forgot I was one of the guys who was for "premium" 91-93 octane gas

:cheers:

BLKingTitan · Apr 18, 2006

When I was in Canada, we mostly saw 85 and 83 octane. The Titan did fine with them for a week and we were filling the tank on a daily basis. I did upgrade and give it a full tank of 91 octane when we hit the states again. You now, kind of like giving the truck a glass of champagne after it had been drinking pond water.:jester: :jester:

DesertNissan · Apr 18, 2006

87 seems to work ok, thats regular around here. Premium is only 91 but like .30 more a gal.... I would probably go 91 always if it were only .10 diff, I use 91 on weekends when climbing the mountains to the cabin.

Scott

EricNY · Apr 18, 2006

I use premium 93. I think it feels better and seems like i get a little better gas milage. To me its worth spending extra on the engine especially if you plan on keeping the truck for a long time. Some times when i get down to 1/2 a tank i will fill with reg 87. I would never put anything less than 87.

virus · Apr 18, 2006

Using premium is a complete waste of money unless it can be utilized. 87 octane gasoline actually has more potential energy than 93 octane does. Most people associate 93 octane gasoline as providing higher performance numbers because of it's use in higher performance vehicles. Any perceived increase in performance is in your head. Over the years I've fallen to many products that I perceived to provide better performance and I too use to believe that premium fuel made my car run better, but after reading the research I marked it up as a dumb mistake on my part. This discussion is always beat to death with those who swear that premium makes their car run better and those who say it doesn't. Unfortuneately for those who run premium, I think you will find they have no definative evidence proving it provides any real benefits. Regular has the same detergency as premium. (it's required by law) Using premium in a vehicle designed to use 87 and vice versa will actually decrease mileage. Neither will decrease mileage by more than a few percentage points.

On the other side however, if using premium makes you feel better and provides you with piece of mind, it's worth every last drop.

virus · Apr 18, 2006

The Low-Down on High Octane Gasoline

--------------------------------------------------------------------------------

From Vincent Ciulla,
Your Guide to Auto Repair.
http://autorepair.about.com/cs/gener.../aa062300a.htm

Are you tempted to buy a high-octane gasoline for your car because you want to improve its performance? If so, take note: the recommended gasoline for most cars is regular octane. In fact, in most cases, using a higher octane gasoline than your owner’s manual recommends offers absolutely no benefit. It won’t make your car perform better, go faster, get better mileage or run cleaner. Your best bet: listen to your owner’s manual.

The only time you might need to switch to a higher octane level is if your car engine knocks when you use the recommended fuel. This happens to a small percentage of cars.

Unless your engine is knocking, buying higher octane gasoline is a waste of money, too.

Premium gas costs .15 to .20 cents per gallon more than regular. That can add up to $100.00 or more a year in extra costs. Studies indicate that altogether, drivers may be spending hundreds of millions of dollars each year for higher-octane gas than they need.

What Are Octane Ratings?

Octane ratings measure a gasoline’s ability to resist engine knock, a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders. Most gas stations offer three octane grades: regular, usually 87 octane, mid-grade, usually 89 octane and premium, usually 92 or 93. The ratings must be posted on bright yellow stickers on each gasoline pump.

What’s The Right Octane Level For Your Car?

Check your owner’s manual to determine the right octane level for your car. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock.

How Can You Tell If You’re Using The Right Octane Level?

Listen to your car’s engine. If it doesn’t knock when you use the recommended octane, you’re using the right grade of gasoline.

Will Higher Octane Gasoline Clean Your Engine Better?

As a rule, high-octane gasoline does not outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car’s engine. In fact, the U.S. Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.

Should You Ever Switch To A Higher Octane Gasoline?

A few car engines may knock or ping — even if you use the recommended octane. If this happens, try switching to the next highest octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking.

Is Knocking Harmful?

Occasional light knocking or pinging won’t harm your engine, and doesn’t indicate a need for higher octane. But don’t ignore severe knocking. A heavy or persistent knock can lead to engine damage.

Is All "Premium" Or "Regular" Gasoline The Same?

The octane rating of gasoline marked "premium" or "regular" is not consistent across the country. One state may require a minimum octane rating of 92 for all premium gasoline, while another may allow 90 octane to be called premium. To make sure you know what you’re buying, check the octane rating on the yellow sticker on the gas pump instead of relying on the name "premium" or "regular."

As a follow up 20/20 last week did a 10 ten myths and higher octane fuel was number 5 on the list with some of the top Master Mechanics and NASCAR crews and drivers backing the above claim.

Last month, the Discovery Channel Show Myth Busters came to the exact same conclusion

Last and most important piece of advice as stated above:

“Using a higher octane gasoline than your owner’s manual recommends offers absolutely no benefit”.

virus · Apr 18, 2006

Octane Number and what it means:

I’ve done a little research and found this more detailed discussion from the February 15, 1988 edition of the “Octane Week” Newsletter. To better help you understand what is being discussed, I've placed clarifying information inside of these { } brackets in the body of this short paper. I’ve also placed the one section of this discussion that requires some knowledge of organic chemistry in these [ ] brackets. You can skip that section and still get quite a bit out of this paper.

~~~~~~~~~~~~~~~~~~~
A Review of the Term “Octane Number” by George H Unzelman of Octane Week’s advisory board.

Recently I was asked to explain the difference between Research {R} and Motor {M} octane numbers. A second part of the question was: Why does the industry use (R+M)/2 octane?

In general terms the octane number of a gasoline is a measure of its antiknock quality or ability to resist detonation during combustion. A little history is helpful in understanding the different methods of measuring octane quality.

Not too many years after the discovery of the antiknock characteristics of ***rethyl lead, {the lead used in leaded gasoline -- see the next post to get the full spelling of this word} it became obvious that some yardstick was needed to define the antiknock quality of motor fuel. The octane scale was developed in 1926 by Dr Graham Edgar. Iso-octane was the hydrocarbon selected as 100 octane because it would not knock in the highest compression engine in existence at the time. Normal heptane, on the other hand, was designated as zero octane because it would cause intense knock in a very low compression engine. Mixtures of the two hydrocarbons established the linear scale between zero and 100. For example 20% normal heptane and 80% iso-octane has an octane number of 80. Later, methods were established to extend the octane scale above 100.

The Cooperative Fuel Research (CFR) knock-test engine was developed to determine {gasoline} octane number in the laboratory. It is a single-cylinder engine in which the compression ration can be adjusted during operation. The knock intensity of the fuel {gasoline} under test is bracketed between standard mixtures of iso-octane and normal heptane or other standard fuels of known octane number.

Two standard ASTM {American Society of Testing Materials} test methods define knock characteristics of motor fuels, by the Research (D 2699) and Motor (D 2700) methods. The Research method correlates with engine antiknock performance at low {engine} speed, while the Motor method correlates with high-speed performance. Both methods employ the same basic laboratory engine under different speed, spark advance, mixture temperature, and intake air temperature conditions.

The Motor method was developed first and was adopted and used extensively by the petroleum refining industry in setting finished gasoline specifications. However, during the 1950’s new refinery processes materially changed the hydrocarbon characteristics of gasoline. The road performance of gasoline no longer matched Motor octane number. Another measure of performance was needed and the Research method became the designating octane quality at the gasoline pump.

Because the Research method is less severe than the Motor method, most gasolines have a higher Research octane. The difference between the two numbers is called sensitivity. [For example a cat-cracked gasoline {component} with a Motor octane number (MON) of 81 and a Research octane number (RON) of 93 has a sensitivity of 12. The sensitivity of gasoline depends on hydrocarbon type and cat-cracked gasoline is “sensitive” because it contains a high percentage of olefins and aromatics. By contrast alkylate and isomerate {other gasoline blend streams} are paraffinic in nature and have little or no sensitivity.]

Sensitivity also relates directly to road octane quality. {Road octane is not defined by a specific lab test, but is the observed performance of gasoline on the road – in actual use in a vehicle on the road.} Following the switch to RON for octane specifications in the 1950’s, oil industry research laboratories worked extensively with instrumented vehicles to determine road octane numbers for the various makes and models. There was almost a frenzy of activity during the so-called octane-race period of the late 1950’s. Detroit auto makers steadily increased compression ratios to achieve superior performance and the oil industry followed with higher octane quality of fuels to match vehicle needs.

Because of the tremendous expense of equipping and operating road test facilities, the oil industry continued to use RON for specifying the octane quality of gasoline at the refinery and at the station pump until 1981. On Sept 4, 1981 the Environmental Protection Agency {EPA} published a notice in the Federal Register to amend unleaded gasoline regulations by substituting (R+M)/2 for RON as a measure of unleaded gasoline octane. Since that time the term “octane number” {at least in the USA} has been accepted as (R+M)/2 unless otherwise designated.

~~~~~~~~~~~~~~~~~
I hope this detailed discussion helps you better understand gasoline octane.

virus · Apr 18, 2006

Thought I would expand a little more on what I posted above on gasoline octane while trying to answer this question and also cover some misconceptions about octane. [All octanes are (R+M)/2].

By using high octane gasoline, we are attempting to prevent engine knock. Engine knock is the premature and spontaneous ignition of gasoline. In effect the fuel EXPLODES rather than BURNS, and this results in incomplete combustion, a loss of power and (over time) engine damage. When this happens, you hear an audible "knock" or "ping", sometimes referred to as detonation. Detonation may vary from a faint noise on light acceleration to a constant, deep hammering noise while driving at speed.

Octane requirements are dictated by the following three engine operating factors:
- Cylinder Pressure,
- Spark Advance, and
- Engine Temperature.

Also, engine deposits can affect all of these factors, and produce engine knock where it otherwise would not exist.

Modern engines (like the VQ35) do a good job of controlling the spark advance and to some extent engine temperature. Cylinder pressure is less well controlled and is more dependent on the environment (the engine’s compression ratio, the altitude where you’re operating and the throttle position). But things get real exciting when you go to maximum power output at WOT (Wide Open Throttle). That's when bad things can happen fast. That is typically one of two times when you need maximum gasoline octane to prevent engine knock. The other is lugging your engine when engine temperatures are high.

Anything you do to increase any or all of these three factors will increase your engine’s octane requirement. So, if you put a turbo-charger on you car, you will increase cylinder pressure. If you’re driving a loaded car up a steep grade at high speeds, you will increase the engine’s temperature (but also slowly decrease the cylinder pressure due to ever higher elevation).

Because many OEMs (Original Equipment Manufacturers) are conservative, their stated octane requirement for their vehicles are frequently based on a series of very strenuous tests on the engine dynamometer that are in all likelihood never seen in the real world. In effect they have you driving at WOT (maximum power) for several hours at a time. The last I checked, all Highway Patrols kind of frown on that.

All of this being true, it is also possibly true that the current VQ35 engine (with a 10.3 to 1 compression ratio and advanced engine controls) is operating on the edge of what can be safely done burning regular gasoline. And this even though the owners’ manual says it can be operated on 87 octane regular gasoline – although they recommend premium. The 3.5L VQ engine in the Maxima is among the most advanced in engine technology today (see Wards Automotive 10 Best Engines for more details). The Honda Accord V-6 advertises use of 87 octane regular, but it only has a 10.0 to 1 compression ratio. Because of this, perhaps the VQ is not so close to the edge with 87 octane gasolines. If you do run 87 octane, I recommend that you work to keep these factors above as low as possible (but there's not much you can do about spark advance).

Now I would like to quote from the 2004 Maxima owners’ manual:
"Use unleaded gasoline with an octane rating of at least 87 AKI (Anti-Knock Index). For improved performance . . . use unleaded premium gasoline with an octane rating of at least 91. . . However, you may use unleaded gasoline with an octane rating as low as 85 AKI in high altitude areas [over 4,000 ft] such as Colorado . . ." {goes on to list all or parts of 10 other high-altitude western states}. I will discuss octane and altitude in more detail later on this thread. Then the owners' manual has a comment {with my interpretation}:

"However, now and then you may notice light spark knock for a short time while accelerating or driving up hills. This is not a cause for concern; because you get the greatest fuel benefit {read 'efficiency'} when there is light spark knock for a short time under heavy engine load." Higher efficiency means better gasoline mileage and when you are very close to getting light spark knock, the engine is apparently at its most efficient. {This is engine lab 101 for Mechanical Engineers.}

You’ve probably heard it said that improper engine timing or excessively lean air/fuel ratios will cause engine knock. Well the engine timing impacts the spark advance factor cited above. And the excessively lean air/fuel ratio will increase engine operating temperatures. So both of these statements are true because of their impact on the important three factors.

Some slight misconceptions about octane and gasoline blending;
1) The higher the octane rating on a gasoline the less volatile it is (evaporative qualities) and the slower the fuel burns.
Comment: While this is correct about the slower burning property of premium gasoline, the volatility of premium gasoline (evaporative qualities) is not directly correlated with its octane rating. The volatility of each grade of gasoline is determined in the blending process (and is usually set as high as the applicable government regulations allow for that time of year). This is because the higher volatility components used to blend gasoline are relatively cheap and have reasonable octane characteristics.

2) Most fuel refiners blend fuels for geographic areas and adjust their blends seasonally.
Comment: All refiners blend their gasolines according to strict EPA regulations for their marketing area and the season of the year.

3) These blending techniques compensate for the decrease in oxygen content with an increase in altitude and compensate for volatility during the warmer or cooler seasons.
Comment: It's not the decrease in oxygen content with altitude that's important, but the lower air pressure at higher altitudes. Because of the lower ambient air pressure, the cylinder pressure is reduced versus the pressure at sea level. Thus, it's possible to use a lower octane fuel at higher elevations without engine knock. Generally above 4,000 feet, 85 octane performs better than 87 octane at sea level. Thus, if you transported (via carrier) a vehicle with 85 octane in the fuel tank from Denver to Los Angeles, you would likely have noticeable knock (unless the engine technology compensated, which it might.)

Comment: Volatility is the ability of the fuel to vaporize. In the 1950s "vapor lock" was a common occurrence because the fuel vaporized in the fuel line rather than in the carburetor. With EPA mandated lower volatility gasolines in use today, you no longer see "vapor lock." What you do see is sometimes difficult starting situations in cold weather (particularly when a cold snap is premature).

virus · Apr 18, 2006

In a recent letter to the editor, Charles Piper complained that in most of Colorado 85 octane gasoline costs as much as 87 octane gasoline further east. I will attempt to answer this and other complaints. (An exception to this octane discussion occurs with turbo-charged gasoline engines – about 2% of the vehicle population.)

There have been a number of technical studies over many years showing that for most gasoline engines, the octane required for proper operation (no knocking or pinging) decreases about one octane number for each increase of about one thousand feet in elevation. The exact decrease is very specific to each individual engine, but the average of about one octane is a close approximation for most gasoline engines. Most vehicles fall in the range of 0.8 to 1.2 octane per 1000 feet. Thus, a vehicle that needs 87 octane at sea level will most likely only need 82 octane in Denver {5,250 feet} and only 81 octane here {at 6,000 feet}. Yet that vehicle is getting 85 octane in both locations. Looked at another way, 85 octane in Colorado Springs should perform comparably to 91 octane gasoline at sea level in most vehicles.

This physical characteristic of gasoline engines was considered when many of the smaller refineries that supply the inter-mountain West were built and later expanded (and some were also closed – 25 years ago there were 3 refineries in Casper, Wyo., and today there is only one). Not all refineries that supply the Front Range are smaller like the five existing refineries in Colorado and Wyoming. We are also supplied by larger refineries such as the Diamond Shamrock refinery in McKee, Texas and the Phillips refinery in Borger, Texas, both of which make higher octane grades of regular for lower-elevation markets.

Because the smaller refineries lack the economies of scale and do not have the more sophisticated refining units of the larger refineries elsewhere in the country, they cannot cheaply produce the volume of octane needed to blend the octane of all grades of gasoline up to the national standard of 87, 89, and 92 octane. So they produce 85, 87, and 91 octane because it performs quite adequately in most vehicles above 3,000 feet in elevation. In the past Shamrock or Phillips may have entered into a "gasoline octane war" by increasing the octane of their Front-Range regular gasoline to 87 octane in an attempt to increase their sales volumes at the expense of other refiners supplying our area. But in the today's stressful refining situation in which all refineries are running flat-out making all the gasoline they can make, there is no incentive to increase octane costs when you cannot produce any more total gasoline volume.

Piper complains that "most new car manuals state that you should use 87 octane fuel." While most do say that, most vehicles do not have turbo-charged engines (which usually require 92 octane at all elevations), and will perform adequately on 85 octane at elevation. And if you read the manual carefully, many also acknowledge that above 3,000 feet in elevation, 85 octane gasoline is an acceptable fuel.

Why aren't we paying less for 85 octane? When I drive east into Kansas or Nebraska, I usually find that 87 octane costs there are more than the 85 octane I bought here. The Denver boutique gasoline we all must now burn will likely increase the relative gasoline cost along the Front Range versus Kansas and Nebraska (where this special fuel is not required), so this relationship of cheaper regular gasoline here will probably change this summer. (A more complete discussion of gasoline pricing would take up another column.)

Finally, Piper complains that his own vehicle does not perform properly when he "drives up Ute Pass daily" {into the mountains west of town}. I have two suggestions for him (other than buying higher octane mid-grade gasoline): 1) down shift to the next lower gear to reduce the strain on his engine and its likelihood of knocking; and/or 2) from time to time manually add a good grade of fuel-injector cleaner (Chevron's Techron for example) to his gas tank to help remove the deposits in his engine that help promote knocking.

The Author, of Colorado Springs, retired from Amoco Oil in 1998 after 35 years with the company.

Mr. B · Apr 18, 2006

I don't have the attention span nor pateince to read all that.....could you summerize it into about 20 words or less?

blktitan1978 · Apr 18, 2006

I don't know, but he knoews his stuff....... or he's good at copying and pasting! J/K :jester:

Good info

virus · Apr 18, 2006

blktitan1978 said:
I don't know, but he knoews his stuff....... or he's good at copying and pasting! J/K :jester:

Good info

It's a cut and paste job. I wish I was educated enough on this subject.

virus · Apr 18, 2006

Mr. B said:
I don't have the attention span nor pateince to read all that.....could you summerize it into about 20 words or less?

I can't really summerize it into 20 words. Basically it means, if the owners manual says to use 87, you get no benefit at all from using 93. It's a waste of money.

jabez · Apr 18, 2006

I Just filled up my tank yesterday (77.00 worth:crying: ) of regular 87 octane.
I think it runs fine with the 87. Once in awhile I throw in a tank of 91 octane.

helomech · Apr 18, 2006

virus said:
I can't really summerize it into 20 words. Basically it means, if the owners manual says to use 87, you get no benefit at all from using 93. It's a waste of money.

And this subject starts again. The Titans computer will change its settings to run better on 93. How much better is debatable, let the debate begin. Where are you Eric. The owners manual used to say 91, but they changed it.

AMDkid · Apr 18, 2006

Fellow Titan owners,
I've advanced the timing by 5 points (using the CONSULT) and run 90 octane or higher. HP was increased by 8 to 9 at the wheels. My Titan and Armada run much better on 90 or higher. When I put a lesser grade in my Nissans I have fuel filter, dirty injectors problems. And I get more miles per tank with 90 or higher Octane.

Titan Octane Requirements

curdog

mtofell

sudden urge

4X4SoCalTitan

pi3yeargrad

BLKingTitan

DesertNissan

EricNY

virus

virus

virus

virus

virus

Mr. B

blktitan1978

virus

virus

jabez

helomech

AMDkid

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