What some of you guys aren't getting is that there is nothing EXTRA to utilize in higher octane. Octane is just an additive to to increase the ignition point of fuel. It doesn't burn longer or better. It is used to stop preignition in high compression motors. The heat that is created from the high compression may cause the mixture to ignite before the spark and cause pinging or even worse damage. Lead used to be used to increase octane. Now it is different chemicals. The only reason you should use it is if you have hot spots in your motor that are causing preignition or if you plan to put a heavy load on the motor the could cause it to ping. Everyone has their own opinion, but science tells the truth.

 

How many timing tables have you looked at for any of those vehicle? I've looked at hundreds of them. The maximum timing advance of the stock tune doesn't take advantage of premium. Now, if a condition exists which is causing the PCM to pull back timing with 87 and higher octane helps then 89 will suffice, because the PCM doesn't advance timing the 6+ degrees that can be advanced when premium is present. I suggest if you're actually seeing a difference consider what might be causing the vehicle to pull timing with 87 and address that problem.

What the tuning tables do well is retard timing. This is to compensate for bad gas and other conditions which would require it. So, if your truck is gaining something from premium its only because there is an abnormal condition which is causing it to lose performance when 87 octane is used. For instance, fouled plugs, bad gas, carbon build-up, hotspot in the combustion chamber, dirty MAF, etc.

Concerning "smoother." Since the knock sensors detect ping and pull back timing it will run smooth regardless of octane though performance will take a hit when timing is retarded.

If you'll give me the PCM codes of each of these vehicles I'll be happy to post the max timing advance for each of them. On the Ranger and Explorer open the hood and look at the top/center of the firewall. There is a box there with a wiring harness attached with a 10 mm bolt in the center. The code is 4 digits (3 letters followed by 1 number) on the white sticker on top.

On the older F150, open the hood. Where the battery is on the passenger side look down the firewall. The computer box is the same as the Ranger box and you can find the code on it. Due to its location a small mirror might help.

Now, there are certainly vehicles out there which have computers which do advance timing enough to run better on 93. Corvettes, some BMWs, some Lexus models, etc. They start off with a timing table made for premium and have enough retard built in (and good knock sensors) to pull back timing rapidly should you put 87 octane in them.

 

When the FFV detects alcohol it does alter the timing -- more than it does with pure gas but not as much as you may think. Adding "normal" premium, it won't see alcohol and isn't going to bump timing by much. The biggest thing it does with alcohol present is run a different air/fuel ratio.

85 octane is usually not found at low altitudes. This is because at higher altitude you can run 85 octane using the same timing as you would with 87 at lower altitudes... and its why if you're driving from a high altitude area to a low altitude area you should not fill the tank with 85 octane.

One of the reasons E85 reduces mileage so drastically is because it's stoichiometric fuel ratio is far richer than gasolene so more fuel is required per combustion event. Vehicles with higher compression (such as turbo and supercharged vehicles) can often gain significant power from E85 due to the compression and more advanced timing they run --- most of them require premium as their lowest octane.

 

I have tried it. i have actually ran 110 octane in my mach, which is tuned for 91. it did nothing. I know this because I was at the track when I ran out of gas and had to get race gas. I didn't run a new best, the car didn't feel anymore powerful, I didn't get any better MPG...

and I'm with ken on this one, the reason it'll seem smoother is the knock sensors.

I'm sure Exxon will put you on their christmas card list though

 

Without a tuner, premium gas will increase your carbon deposits & make your spark plugs harder to get out per a Ford Field Service Engineer.

 

Well lets just say that those that know the ECU maps real well know darn well the lack of potential of using premium, in an 87 tuned vehicle is not going to buy you thing. As many have said you have to change the maps!
ECU maps written for 87 octane are not open ended to allow much advance, or a big change in air fuel ratio based on octane of fuel. The air fuel ratio has to meet near the stoichometric ratio of 14.7:1. It's an emissions and catalytic convertor efficiency statement.

In flex fuel vehicles the maps are switched once the sensor tells the ECU ethanol is present. Unfortunatley since a FF vehicle is a hybrid design to use two types of fuels the design of the engine platform is a contributing factor to take full advantage of E85.
So if you feel it's amazing or not, it's the facts.
So go play and spend your money, like others have said it's your money!

FTE KEN - exactly!

 

FTE Ken: I no longer own the Ranger, Explorer (money pit) nor the '02 F150 so I am unable to provide you the info you desire. I was simply stating my experience with these vehicles when running 87 vs 93. I'm very maticulous with my vehicles, like many here, and watch for any change in performance no matter if it's gasoline/E85, air filter, tire pressure, brakes, etc. The Ranger was an FFV motor, but at the time of owning it there were no local E85 stations, so I do not know how this truck might have performed while running ethanol.

Now I may not have all the logistics to how the PCM works, this isn't my specialty. I'm sure everyone who has stated the specs and workings of the PCM are correct, I've never doubted this. I was simply stating my experience. No matter what the specs, I have seen a difference, no matter how insignificant it may be. So for the majority of people, they may not see/feel any difference.

I'm unsure how altitude may play a difference in the octane rating and don't know why 85 is okay at high elevation and not at lower elevations. I live in Denver, CO (5280 ft elevation) and have traveled up to roughly 10-11K ft elevation on trips through CO. My experience has shown me that running 93 has provided roughly 9-13 extra miles per 3/4 of a tank (roughly .5-.7 mpgs gained) on these trips in my former '02 F150 vs running 87. It is a small number considering the amount of gasoline used and surely isn't worth the additional cost.

So I appreciate everyones insight and knowledge on this subject, it does provide some good feedback on the issue. Just trying to point out that yes the specs state one thing, but like many of those late night commercials state in the fine print "results may vary". Again my results haven't varied greatly and don't justify the additional cost. Just stating my experience with the different octane rating.

 

In a high-altitude instance cylinder pressures are lower at altitude due to the reduced engine breathing, so there is automatically a reduced need for rated octane.

 

The thinner the air the lower the effective compression of the air/fuel mixture in the cylinder. The higher the compression is, the higher the octane needed to run the engine without pinging. So, at high altitudes 85 octane can run with the saming ignition timing advance as 87 does at low altitudes. Take 85 down to low altitudes and pinging starts to occur. The engine pulls back timing to prevent it and ends up sacrificing economy and power.

 

Do you understand know what I mean about 'fuss'? How about I call it bickering. BTW we are not talking absolutes here, its not scientifically impossible to have any kind of benefit like some have said. There are a lot of variables at play. And even the octane rating itself... heck you could potentially notice a difference even with the exact same octane rating just between brands, etc. The rating is not an absolute its just an average after all, (R+M)/2... and what works best could even vary based on your driving style, and gearing, resulting in different average rpms... etc etc.

 

Agree 100%. I'm finished with the fuss/bickering. Just tried to provide my 2 cents. On to bigger & better threads!

 

Please go back and research how octane is obtained it is an avergare of RON +Mon, but by law it has to equal the numerical output as adverised, so 93 = 93 no matter which method reports its highs or lows . RON and MON are two different methods of measuring octane.

Gasoline is subjected to two testing methods to establish its octane rating: one, called the motor method, runs
the gasoline in an engine running under load; and the second, the research method, runs the gasoline in a freerunning
engine. The research method gives slightly higher ratings, and the octane number displayed on the

pump is an average of the two test methods.

Maybe this article will oput to bed the myth of difern brands!
DRIVING; My Gasoline Beats Yours (Doesn't It?) - New York Times

nuff said!