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Which octane rating of gas do you use?

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When I picked up my new Thunderbird, the dealer told me that I could simply use the lowest gas octane and the car would be fine. But the owner's manual indicates that it's best to use a higher octane level. Because of that, I've been using "Premium" gas ever since, but it does eat into the wallet a bit, especially out here in San Francisco. (Ouch!) Knowing absolutely nothing about cars, I thought I'd ask you experts what type of gas I should be using.


See last post for answer- https://forums.fordthunderbirdforum.com/threads/which-octane-rating-of-gas-do-you-use.436/post-72779

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I own also own a Lincoln LS with same engine as the TBird. The LS drivers mauual states never use below 91 octane fuel.I didn't notice anything in the Birds manual, but I really didn't look, as I always use 92 or 93 octane.
Ed
 
I use 93 exclusively. Since we expect only about 10,000 miles/year (or less), seems like a good investment to avoid problems and get better performance. If (when) premium gets to $2/gal, or we start putting on more miles, I may have to rethink. For now at about $.20/gal difference between 87 and 93, that is only about $95/year at 21 mpg.
 
Here in Amarillo, Tx. with our altitude being 3,780' the highest octane premium pump gas we can get is 90. But have had no problems of any kind. Octane is always higher at sea level and then the refinerys lower the octane levels as altitude increases. Has to do with the atmospheric pressures. PSI lowers as altitude increases.

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Yellow/Yellow Prem. 02 Bird w/full accent
1999 F150 Super Cab 4x4 Off Road
1998 Taurus SE Sport 24V
 
When I picked up my new Thunderbird, the dealer told me that I could simply use the lowest gas octane and the car would be fine.


See last post for answer- https://forums.fordthunderbirdforum.com/threads/which-octane-rating-of-gas-do-you-use.436/post-72779
Who you going to listen to, some car saleman on the car lot aka "the dealer" or the engineers that made the car? Obviously Ford didn't say use high octane for fun.
Also, on low octane cars, people put high octane in them too. The Ford mechanics at the dealership I worked at several years ago told me not to put high octane fuel in the cars that said 87 in the owners manual or it could actually cause problems. They said some people had actually had high octane fuel related problems. Also, if you watch TV reports or read articles, high octane fuel is a waste of money and does nothing more than give the owner a false sense of security and a warm fuzzy feeling like he is taking better care of his car. All of the fuels are equally good for the engine. You should never need high octane fuel on a car that does not knock.

That's my 2 cents.
 
In Central NY, I am fortunate to have access to many stations that carry ethanol free premium gas.. I always use the Octane rating that in the manual which is 91.. Never heard a ping/knock yet from our 02, and she also runs very smooth.. That being said, ours is not a daily driver. With the cost of the non ethanol premium 91, at about $.50 -60 cents more a gallon I'm only filling it maybe once every 6 or so weeks during the driving season here in NY.. If it was a daily driver then I would reconsider..
 
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I have a couple of old cars and I was told to use the lowest octain gas you can (without pinging) because the higher the octain the more eythinal there is in the gas. And that is what causes problems on older cars.

Would that be the same for our T birds? Does only one use 87 or 89 suscessfully?
My dad is a car enthusiast as well and we both agree in higher performance engines or engines with upgrades either way we both use nothing but shell 93 octance v power or the top of the line Exxon 93 octane I think neither or is the best although I ha e gotten better fuel economy out of Exxon 93 Hope this helps
 
In newer cars, you use what the manufacturer calls for, or you are just wasting your money unless you have the SCT Tuner with tunes optimized for different Octane fuel. For example, in my Mustang I have tunes for 87,89 and 93 octane fuels.
 
I found an excellent write up about using various octane levels in our 2002-05 Birds. Unfortunately I did not get the authors name to attach to this.
There fore I'm telling everyone who reads the these are not my words.
You will find this, I think very interesting & probably answers many of your questions.

Should or shouldn’t use hi octane premium fuel

I hesitate to chime-in here because I always end-up getting beat-up when I've either posted this or opened this dialogue with friends and/or automotive enthusiasts. There is so much myth about gasoline and how it impacts a MODERN engine. I assure ALL of you that you are flushing money out your tail pipes.

I'll explain...

The 3.9L engine in your Thunderbird is a high-compression (performance) engine, with a compression ratio of 10.75:1. Regardless of what gasoline you put into the tank, the compression is NOT going to change. ALL gasoline has the same energy content...PERIOD!

• ALL gasolines sold in the United States have fuel additives which clean the combustion chamber. There is no increase or decrease in the amount of (nitrogen-based) cleaning additive in any given gallon of U.S. gasoline. These additives are required by FEDERAL law. These additives will clean carbon deposits as the additive in the gasoline comes into contact with the internal engine surfaces. Though, different fuel retailers will label their fuel additives by differing marketing terms, it's ALL THE SAME cleaning performance. Adding a bottle of fuel injection cleaner, etc. to a tank of modern gasoline is wasted money (and depending upon the chemicals in that fuel-injection cleaner, potentially harmful to engine sensors). The same cannot necessarily be said if you fill-up in Mexico.

• Gasoline-air vapor will self-combust (that is, ignite/explode) when compressed. Modern gasoline has additives in the fuel which helps it resist this phenomena...dependent upon the level of additive in the fuel, the more resistance that fuel-air mixture has to combustion under compression. That level of resistance is known as 'octane'. There are several different ways to measure its resistance, but in the United States we use the (R+M/2) method. This is the number posted on the pump.

• All MODERN engines have acoustic "knock" sensors installed on them (your Thunderbird is no exception) which detect pre-ignition/pre-detonation (a.k.a. "knocking" or "pinging") constantly (hundreds of times per second). If the sensors detect engine/spark knock, the ECM automatically and instantaneously adjusts the spark timing to back-off of the ignition advance to eliminate knock.

• If you put 'regular' (87-octane) gasoline in your tank, and start your car, it will run and idle just fine. As you drive it gingerly down the road, it will run and perform just fine. As you accelerate hard (put a demand on the engine for more performance), the ECM will advance the ignition timing to account for the milliseconds of expanding ignited fuel energy so that the engine can get the most efficient use of that energy to push the piston down. At the same time, the ECM is listening for spark-knock. If the ECM detects spark-knock, it will back-off of the ignition advance (slightly) until the spark-knock is no longer detected. This happens hundreds of times per second, and is indiscernible to the human ear or other senses. When the ignition timing advance is 'retarded', the engine is not operating a 'peak' performance, and therefore, you are not able to eek the maximum engineered horsepower out of the engine at that
moment. This would be known as a performance 'degradation'. Since your Thunderbird engine is naturally-aspirated (not turbo-charged or super-charged), the instances of pre-ignition/detonation is minimal (comparatively-speaking).

Now, with all that said, what does this really mean to a lay-Retro bird-driver? Well, if you decide that you don't want to pay an additional ~50¢/gallon at the pump and opt to fill the tank with 'regular' (87-octane) fuel, you're going to save about $9.00 per fill-up. If you drive your Thunderbird as a cruiser, you're going to realize little to no difference in the performance of your car. You will NOT gain or lose any MPG (remember, there is no difference in energy content of premium fuel versus regular fuel (or anywhere in-between))! Now, if you drive your car like you stole it, accelerate hard from a stop, and put your foot into it when your "accelerating" on the highway, you may be able to notice, or I should more accurately say "measure", a minor horsepower reduction as opposed to the same driving-style with a tank of 91-octane. Why? - Because the ECM is detecting spark-knock and retarding the ignition advance to eliminate it, which takes away from the maximum-engineered engine performance potential. So, if you don't drive your Thunderbird hard, you can opt for 87-octane fuel and save yourself approximately $450 annually which you can put into your maintenance fund, or spend otherwise.

Ford has included this information (from its engineers) in your operator's manual:

"Your vehicle is designed to use 91 “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. Do not be concerned if your engine sometimes knocks lightly. However, if it knocks heavily under most driving conditions while you are using fuel with the recommended octane rating, see your dealer or a qualified service technician to prevent any engine damage." (Keyword: "optimum", "may").

If you understood all of that, consider yourself a wiser consumer. Don't let myth, marketing, or outdated information ruin your wallet
 
all above makes me wonder?? I think I heard in forums that our cars "learn" our driving habits and perform accordingly so if the car is changing its timing to compensate for the knock ,does it learn what its doing till it can't compensate any more? I have friends with a subaru that *requires* 91+ and if the run 87 it slowly starts running bad then it gets really bad they put 91+ back in and it runs good again.maybe because it does not have to compensate any more?.
on the other hand I awn a big bore bike that requires 87 and those that put 91 in them everything about it just goes to crud.like mpg,speed acceleration
I will stick with the "ethyl". (thinkin some of you have not heard that term in awhile) ÖÝÖ
 
For everyday driving Shell 93 octane from specific local Shell gas station that keeps fresher fuel and does not dilute (mix) with other grades.

For track days 100 octane race fuel from pump at secret station.

My car is modified and dyno'ed.

fullsizeoutput_4a7.jpg
 
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When my wife and I test drove our 2005, it had audible pings when pushed hard. For this reason I will only use premium in this car now. I have a Focus ST with a turbo that can adjust to the octane of the fuel you put in, it will never ping audibly. It is not labeled "Premium Fuel Only", but rather recommended for best performance. A good rule of thumb regarding pinging, if you can hear it is definitely doing damage to the engine, if you can't hear it, it still may be damaging your engine. Don't take the chance to save a few $$. Ford didn't put that label on there to cost you more money, they did it to protect against warranty claims.
 
I have a couple of old cars and I was told to use the lowest octain gas you can (without pinging) because the higher the octain the more eythinal there is in the gas. And that is what causes problems on older cars.

Would that be the same for our T birds? Does only one use 87 or 89 suscessfully?
So, even with the lower hp of the 2002 models, we are getting more horsepower out of 3.9 liters than we used to get on premium in 5.0 thru 5.7 liter engines. These 3.9s are already ported with 4 valves per cylinder and more aggressively camed and computer controlled to narrower margins to achieve that power. Reducing octane may more easily cause pinging and reduced power and poor drivability because these engines are more finicky. Many classic car drivers look for stations that sell no ethanol premium to avoid issues with the alcohol in the fuel and provide the real octane the engine is designed for.
 
So, even with the lower hp of the 2002 models, we are getting more horsepower out of 3.9 liters than we used to get on premium in 5.0 thru 5.7 liter engines. These 3.9s are already ported with 4 valves per cylinder and more aggressively camed and computer controlled to narrower margins to achieve that power. Reducing octane may more easily cause pinging and reduced power and poor drivability because these engines are more finicky. Many classic car drivers look for stations that sell no ethanol premium to avoid issues with the alcohol in the fuel and provide the real octane the engine is designed for.
Different octane fuels burn at different rates. When the manufacturer sets a minimum octane standard that is what it will need for normal operations. Yes, we are lucky to have computers smart enough to adjust to what it sees as poor quality fuel to preserve the engine , but keep in mind engineers design fuel and ignition mapping that the computer uses and when you make changes like lower octane fuel you are forcing the computer to work along the areas of the maps where at times the computer cannot fully adjust and therefore cannot adjust timing or fuel mixture properly. In my mind it’s simply not worth it.
It’s like using a poor quality oil. Works fine until that one hot day where the oil can no longer protect and the engine destroys itself. Not worth it!!
 
I use either Shell 93 and or Sunoco 93, I travel to NJ about twice a year except for last year cause of the Virus, I get 25 MPH with my 3.9 with shaved heads and Borla exhaust
 
My 2002 with 68K miles gets pretty much book spec for miles per gallon. Out on the open road it does about 24, I think. That is perfectly acceptable
in my book. In the northwest at 2000 feet our premium is 91 Octane, and where I can I buy alcohol free unleaded Premium.
 
Use what the owner's manual states (premium) and you'll be fine) as to the original post about the member also having "older cars"; if those go back to the 60's that is an entire 3-4 steps back in technology, no computers, no MAFs, and no electronic fuel injection and the "ping test" was more relevant back then, cars can detonate before you actually hear it which is not good but you could usually get away with it with vintage cars.
 
Only premium, and in the case of my regular gas station that would be 92 octane. In Texas we’re fortunate to have very low fuel prices and since I drive her 1-4 days a week, filling up for at times $1.97/gal premium is plenty doable twice a month. Now gas is going up again but coupled with my points discount from grocery shopping I rarely pay full price for gas unless I’m out of town.
 
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