3.9 and premium fuel

[DealerDude]

for best performance use 91. if in high altitudes you must use 91. if you use less than 91 and hear engine knock, go back to 91 or engine damage will occur.

I just copied this from the on-line owners manual."“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."

 

[Icewine]

Just purchased a 2002. Has 9000 miles. Manual recommends 91 octane is that necessary?
Any recommendations on a UV protectant for dashboard

If the factory says it is necessary I couldn’t imagine taking the word of anybody else as to whether or not it is. Every manufacturer employs engineers that develop such recommendations based on science and research. Ford has nothing to gain when you purchase 91 octane fuel for your Thunderbird, so why else would they recommend you do, other than the performance and longevity of your vehicle?

 

[Bark624]

I tend to error on the side of caution. If the extra 50 cents a gallon is an issue then I don't know what else to say, other than sell it.

 

[David S]

I only use regular, never a problem - at low altitude.

 

[JW in Dixie]

for best performance use 91. if in high altitudes you must use 91. if you use less than 91 and hear engine knock, go back to 91 or engine damage will occur.

2004 T bird: My other Ford large V-8s have run on 87 with no problem. Are you saying that the computer can't compensate? Thx - trying to learn

 

[The Flash]

I am not a Ford expert. I can only say what I have found on the inter-net (so it must be true) LOL.
These TB's do NOT know the difference between octane ratings like many newer cars can and their EMC makes the ignition timing and fuel load adjustments to compensate for the lower or higher octanes.
TB's use knock sensors. When they feel the engine knock due to lower octane or other issues like temp. or altitude, they retard the timing and make adjustments to lower the power so the knock stops. For a while, then when the knock comes back it adjusts.
So for all those that don't care about power or fuel mileage and think your TB runs fine it's the computer lowering the power. Not a good thing. Use the proper octane 91.

 

[tbird]

These TB's do NOT know the difference between octane ratings like many newer cars. Not a good thing. Use the proper octane 91.

I agree with you, my Mustang is much newer and I have a SCT Tuner for 87, 91 & 93 octane fuel. The car has to be tuned accordingly to match the octane fuel. There's a reason why the engineers called for the 91 octane fuel.

 

[BIRDSALL]

I remember when I first got my bird I was driving in Myrtle Beach one day and noticed a gas station with much lower than usual prices for the time. I had about a quarter of a tank and decided to fill her up with “regular” gas. That was the first and last time I did that. Before I had reached the next traffic light the car lost much of its acceleration from both a stopped position and a moving position. It had nothing to do with the station, hundreds of people use it every day and it’s still open. Due your self a favor and just use the higher more expensive octane fuel. Your car will love you for it and give you years of pleasurable driving..

 

[BIRDSALL]

One final note..I stopped at an auto parts store and bought octane boost which corrected the problem until my next fill up.

 

[JW in Dixie]

One final note..I stopped at an auto parts store and bought octane boost which corrected the problem until my next fill up.

Typical fillup for my 2004 is 17 gals x .50 = $8.50 which will pay for a can or 2 of booster. Thx

 

[The Flash]

One 15oz bottle to treat 20 gallons of gasoline of Lucas octane boost is $7.49 plus tax.
In Las Vegas 91 Octane cost 23 Cents more than 87.

 

[The Flash]

Just got gas at Sam's and 91 octane is 33 cents higher than 87 today.