Which octane rating of gas do you use?

[biddle]

You should use the recommended fuel grade or higher. Many will say otherwise but the engineers who designed the car would disagree.

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[wredhorse]

My 2003 owners manual says 91 octane.

 

[RDH]

nothing but Shell 92 or Sunoco 260, anything else always High Test

 

[biddle]

Each person is entitled to their opinion about this issue, so do what you personally think makes you comfortable.

If I feel comfortable, I can use Diesel fuel? Obviously the engineers that made the car didn't recommend premium fuel for fun, as a matter of fact, this is not a good selling point for the car, so they would not have made this recommendation unless it was necessary. Unless your credentials are greater than an engineer at Ford Motor company, your opinion likely doesn't really matter, right? This is what makes buying a used car so tough.

 

[Big Al]

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.

The lower rated octane is probably acceptable seeing as the engine computer will retard the distributor advance to prevent it from detonating (pinging). The draw back to this is reduced power. You might want to alternate between octanes, refilling when it is half empty (full).

93 ocatane is running around $1.25 plus or minus some pennies depending on the station. I can go about 2 weeks on a tank as a daily driver.

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I thought I read in the manual that you are to use 91 octane I think it says so on the gas cap. 91 will give better performance. My other cars say 87. Using octane higher than demanded is a waste of money. The car cannot use the higher octane to any advantage. The 'Birds need it and can use it because of the 11 to 1 compression ratio. I have two Prii that have an Atkinson Cycle engine with 13 to 1 comp. ratio and they can use 87. But that system is very complex> I can't explain it but I think it is a type of lean burn exhaust gas recirculation set up.
The best fuel economy I have recorded was going 60-63 MPH on a warm, but not hot day with a tailwind and slight uphill terrain. 27. MPG. Were I disciplined enough to go 55 I could get much better........I JUST CAN'T DO IT! To much fun to get on it. Going to a Convertible Cruise 4 day event with a load of luggage (even filled up the top bay) and two aboard, going 75 plus on I-35 with a tailwind, I recorded 25 MPG. Darn good for a 24 highway rating and a car weighing 3800 lbs empty.

 

[JAT]

I use premium Chevron. The reason for Chevron is because I’ve seen inside an engine before and after using Chevron with Techron and it completely cleaned up a carbonized cylinder head after using it for awhile! I was sold!

MODERATOR NOTE:

 

[Issyro]

I cheat as I always put in half 87 and half 93 octane at the same fill up! That gives me an average of 90 of octane and I’ve been doing it for years.

 

[RDH]

No knocking on my 03, and nothing but 93 octane, cause I had the engine built after the head gaskets blew, heads were shaved and Bola exhaust, and more horsepower, no low test for me

 

[RDH]

I don't understand why anyone would use anything buy 93 octanes, Mine is a Jaguar engine, 3.9 as is the tranny. I've had it for over 5 years and the only problem I had was the head gasket blew and then the suspension fixed, other than that she runs great, 68000 plus miles

 

[biddle]

I don't understand why anyone would use anything but 93 octane

People think they are smarter than the engineers of the car, and misinformation or like one person said "Each person is entitled to their opinion". You are entitled to your opinion, but if your opinion is different than someone with a PhD who made the car, it's wrong.

The real question is why people don't use what octane the engineer calls for that made the engine.

Anyone who has used a SCT Tuner knows, you need to use a programmer and custom tune on modern engines to fully capitalize on a higher octane fuel than the car is designed for. It doesn't magically adjust to everything needed. I have 87,89,93 tunes for my Mustang. If I change octane, I have to change the tune to match it.

With that said, I'm closing the thread to prevent more misinformation from being spread. It's common sense that Ford didn't say to use high octane fuel for fun, but as Voltaire said, common sense is not so common. You will see nowhere in the owners manual anything that says you can use 87 octane fuel because it's a modern engine and "will adjust for it". You have to buy a Tuner like an SCT Tuner and change many engine parameters to leverage different octane fuels!