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Topic: What grade of gas? (Read 2747 times) previous topic - next topic

What grade of gas?

My grandparents are giving me their 1988 Cougar 5.0 V8.
My grandfather says that the manual says to use regular, but from what i know the cougar has a performance engine so it hink it needs premium?
So regular or premium?

Re: What grade of gas?

Reply #1 –
If your Cougar has the stock (or even the HO) 5.0 regular is the best fuel to use. Unless the compression ratio was raised or you're running a blower or the timing has been advanced you would not need anything more expensive.
2015 Mustang GT Premium - 5.0, 6-speed, Guard Green - too much awesome for one car

1988 5.0 Thunderbird :birdsmily: SOLD SEPT 11 2010: TC front clip/hood ♣ Body & paint completed Oct 2007 ♣ 3.55 TC rear end and front brakes ♣ TC interior ♣ CHE rear control arms (adjustable lowers) ♣ 2001 Bullitt springs ♣ Energy suspension poly busings ♣ Kenne Brown subframe connectors ♣ CWE engine mounts ♣ Thundercat sequential turn signals ♣ Explorer overhead console (temp/compass display) ♣ 2.25" off-road dual exhaust ♣ T-5 transmission swap completed Jan 2009 ♣

Re: What grade of gas?

Reply #2 –
haha, performance engine, we all wish

Re: What grade of gas?

Reply #3 –
Quote
...performance engine....

 :rollin:  :rollin:  :rollin:  :rollin:  :rollin:

Just to add my  :2c:, i alway use premium and I can say i do better mileage than regular.... and since this "performance engine beast" is so lazy, i also got better response and acceleration.

IMO, The +0.06c/L worth it...

The puma : Dont forget Cougar may be having a 5.0 but its a 5.0EFI (150HP) vs a Mustang 5.0HO (225HP).

BTW Welcome to the board.....  :cheers:

Re: What grade of gas?

Reply #4 –
Sly: Back when I was in trade school our class had a representative from the Imperial Oil refinery give a guest lecture. He told the class this:

Premium fuel will do absolutely nothing for a low compression, stock engine with the stock ignition timing. The higher the octane the slower the fuel burns, so using premium in an engine that's not designed for it can actually hurt performance and economy as the fuel is not burning at the rate for which the engine was designed. Premium gas does not burn any hotter, nor does it produce any more power when it burns. The octane rating is merely a measurement of the fuel's resistance to detonation. Detonation is prevented by slowing down the burn rate.  When a car has an engine design that involves elevated combustion chamber temps (such as high compression, forced induction, or advanced timing) then, and only then, will you see a differnce with high octane stuff.

I have done a bit of reading on the subject, in car magazines, textbooks, an Imperial oil industry product guide, and of course the internet, and evrything I have read indicates that putting supreme into your tank when the owner's manual calls for regular accomplishes nothing more than making oil companies richer.

I would bet that your perceived fuel economy and performance figures are the result of your subconcious trying to convince you that the extra 6c/liter is worth it :D
2015 Mustang GT Premium - 5.0, 6-speed, Guard Green - too much awesome for one car

1988 5.0 Thunderbird :birdsmily: SOLD SEPT 11 2010: TC front clip/hood ♣ Body & paint completed Oct 2007 ♣ 3.55 TC rear end and front brakes ♣ TC interior ♣ CHE rear control arms (adjustable lowers) ♣ 2001 Bullitt springs ♣ Energy suspension poly busings ♣ Kenne Brown subframe connectors ♣ CWE engine mounts ♣ Thundercat sequential turn signals ♣ Explorer overhead console (temp/compass display) ♣ 2.25" off-road dual exhaust ♣ T-5 transmission swap completed Jan 2009 ♣

Re: What grade of gas?

Reply #5 –
Hey TC - random question: at what compression ratio would you start using higher octane gasoline?
1984 Cougar Convertible
1988 Cougar XR-7

Re: What grade of gas?

Reply #6 –
That's not a clearcut question. There are many factors: Combustion chamber design, cylinder head material, ignition timing - they all have just as much of an effect on octane requirements as the compression ratio does. That being said, I have no idea what you would use as a cutoff point :D
2015 Mustang GT Premium - 5.0, 6-speed, Guard Green - too much awesome for one car

1988 5.0 Thunderbird :birdsmily: SOLD SEPT 11 2010: TC front clip/hood ♣ Body & paint completed Oct 2007 ♣ 3.55 TC rear end and front brakes ♣ TC interior ♣ CHE rear control arms (adjustable lowers) ♣ 2001 Bullitt springs ♣ Energy suspension poly busings ♣ Kenne Brown subframe connectors ♣ CWE engine mounts ♣ Thundercat sequential turn signals ♣ Explorer overhead console (temp/compass display) ♣ 2.25" off-road dual exhaust ♣ T-5 transmission swap completed Jan 2009 ♣

Re: What grade of gas?

Reply #7 –
Quote from: Thunder Chicken
The higher the octane the slower the fuel burns, so using premium in an engine that's not designed for it can actually hurt performance and economy as the fuel is not burning at the rate for which the engine was designed.

The difference between the "burn rate" of premium and regular gasoline is negligible. Here is some tech to back that up. A 10hp Briggs&Stratton engine running on 87 octane or 104 octane will make the exact same power. The 104 just costs a lot more.

Re: What grade of gas?

Reply #8 –
I think of premium as harder to ignite, not much else. It may be slower burning, but thats the least important aspect of the stuff. Why else would we use it other than to prevent early detonation
1988 Thunderbird Sport

Re: What grade of gas?

Reply #9 –
Quote from: Seek
I think of premium as harder to ignite, not much else. It may be slower burning, but thats the least important aspect of the stuff. Why else would we use it other than to prevent early detonation


That's exactly what higher octane does, resist self ignition, which is detonation or preignition. They may burn at the same rate, but regular takes less effort to ignite. :ies:
95 Ranger Splash 2.3
88 Tbird Sport :ies::ies:
5.0 SO, stainless shorty headers, w/ Magnaflow lers. KYB struts, KYB shocks. 5lug conversion from sn95 Mustang, subframe connectors, drilled and slotted rotors, 03 Mach 1 wheels. sequential taillights.140 speedo

Re: What grade of gas?

Reply #10 –
Thats what I don't get about people who think that using premium because it "burns slower" will give them better gas mileage. :dunno:

Even if it does burn slower, how much? 5%? 3? .000000824? Doesn't matter as the fuel isn't available for that purpose
1988 Thunderbird Sport

Re: What grade of gas?

Reply #11 –
Actually could hurt performance. There was an article in MM&FF a few years ago where they tested different grades of gas in a mildly modified 5.0 Mustang. The results were that using more octane then needed actually slowed the car at the dragstrip. It was only 3 or 4 tenths, but every tenth counts..lol. If you not experincing (sp) pinging on 87 then you are probably fine. :ies:
95 Ranger Splash 2.3
88 Tbird Sport :ies::ies:
5.0 SO, stainless shorty headers, w/ Magnaflow lers. KYB struts, KYB shocks. 5lug conversion from sn95 Mustang, subframe connectors, drilled and slotted rotors, 03 Mach 1 wheels. sequential taillights.140 speedo

Re: What grade of gas?

Reply #12 –
I don't see the point of using premium for better fuel economy unless you have a performance engine. With the amount you spend on a tank of premium you could buy a couple of extra gallons of regular for the same price.