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  #1  
Old 12-30-2003, 09:02 PM
grizz5675 grizz5675 is offline
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Question 5.4 low octane gas use

In my maintainance book for my 2001 5.4 motor it states; use 87 octane gas especially if gas is from the us, I have always owned older ford trucks and have used 90 plus octane thinking it would burn cleaner my question is does anyone know why ford recommends the lower octane rating ?
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Old 12-30-2003, 11:19 PM
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Ford recommends 87 Octane because that's what the engines are designed to run on. Many factors (timing, compression ratio, etc.) play a part in determining Octane requirements. Most standard duty engines today only require 87 Octane.
Unless you have significant detonation / preignition problems (probably indicating a problem elsewhere) there is no advantage gained by running higher Octane fuel.
Actually, there can be detrimental side effects (or so I read).
It is possible your older engine had a higher compression ratio. Also, as engines age, carbon deposits in the combustion chamber can raise the effective compression ratio leading to the need for higher octane fuel.
Higher Octane fuel will not burn "cleaner" in your new 5.4 motor.
But, to be honest, I'll sometimes but 1/2 tank of 93 to mix with the 87 I have in the tank already. As fuel formulations change with the seasons, sometimes I will experience a little pinging. It only takes about 1/3 tank of 93 mixed with the 87 to eliminate it.

I see this is only your 3rd post. Welcome to FTE! Hope you like it and stick around.
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Old 12-31-2003, 08:47 AM
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Thank you for your fast reply , I guess the octane rating question basically stems from the old saying "its hard to teach an old dog new tricks" and thanks for the welcome.
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Old 12-31-2003, 09:51 AM
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You are welcome, and again, nice to have you here.
A little more info...based on all I have read, Ford (as do others I am sure) designs and tunes their engines to eek the most performance possible out of 87 Octane fuel. Todays On-board computers and advanced electronics do a good job of managing all the variables (fuel-air ratio, engine timing, etc.) to keep pinging to a minimum and at the same time, deliver the most efficient power possible.
Todays engines do actualy "listen" for pinging and will alter engine variables real-time to reduce and/or eliminate it.
Now, I'd imagine if you throw in towing, heavily loaded vehicle, ambient air temp, specific gas formulation, barometric pressure, etc., one could find themselves running in a fairly constant state of the OBC having to retard timing. Perhaps this might result in a slightly lower mpg number. In such a case, a diet of 89 octane might be in order.
I have tried different brands of gas and found that my truck (4.2 V6) prefers Shell 1st, then Chevron 2nd. Amoco works OK. Exxon for whatever reason, tends to ping more than any other, and even then it is not real bad. I haven't run Texaco in a long time, but it seemed to do OK. We once had a Mustang that loved Philips 66 gas. But, there isn't a Philips 66 convenient to me now.

Anyways, here is something more to read - from people that know far more than I do!
http://www.chevron.com/prodserv/fuel...i_octane.shtml
See you 'round
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Last edited by BrianA; 12-31-2003 at 09:53 AM.
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Old 01-02-2004, 12:35 AM
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Unless you add a performance chip that changes the spark advance and fuel curve, the only faster about using 93 octane is how fast your wallet goes empty.
I have towed over 6000lbs in 98 degree heat in my 2001 running 87 octane and I have never had a problem.
Now my Mustang has the timing advanced and a few other mods and it runs best on 93 octane unless I bump the timing back down to about 10 deg. Then is doesn't make as much power.
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Old 01-08-2004, 12:03 AM
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Just FYI I've found that not all gas is truly created equal, different brands of the same octane can have differing BTU contents. To clarify the octane rating deals with how quickly the fuel burns(higher number, slower burning; hence less pinging) the BTU content is how much energy is contained in the fuel. I can't remember the exact order, but I do recall Chevron, Shell, and Citco near the top and Exxon being near the bottom.
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Old 01-08-2004, 12:28 AM
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I use Citgo and have nevr had a problem.
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Old 01-08-2004, 01:41 AM
grizz5675 grizz5675 is offline
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all gas retains a certain amount of moisture, premium contains the most,which most people would think the opposite.My brother owns 3 gas stations[conv.stores],thats the only reason i know this ,just thought i'd pass that along.
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Old 01-08-2004, 01:41 AM
 
 
 
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