Which octane to use?

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Jul 5, 2006 | 11:30 PM

#16

DOHCmarauder

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From: Las Vegas

Quote:

Originally Posted by orgnova

92merc

that is what i said, yes it has to do with energy, without it, you go nowhere

Realize that's what you said................and it's still wrong.

If your motor does not need the higher resistence to knocking (pre-ignition) you are LOWERING the performance of your vehicle.

If your motor does not detonate, revs smoothly etc....going to a higher octane will do NOTHING unless you raise compression, advance timing etc..

That being said, my '01 V10 asks me politely for mid-grade when towing, especially at 120*........

Jul 5, 2006 | 11:36 PM

#17

tdister

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From: central TX

Quote:

Originally Posted by DOHCmarauder

If your motor does not need the higher resistence to knocking (pre-ignition) you are LOWERING the performance of your vehicle.

Not necessarily. Which reasoning do you stand behind on this statement? That it burns slower? Less energy?

Jul 5, 2006 | 11:37 PM

#18

DOHCmarauder

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From: Las Vegas

Quote:

Originally Posted by KW160

I'd like to hear the reasoning behind that theory...

Don't know if it's true or not, but here's the theory;

If you run a higher than needed octane, it's possible that you're NOT getting a complete burn since the higher octane fuel rating resists ignition....especially on a lower compression motor.

Now you're building up carbon and creating hot spots in your combustion chamber.........when trying to go BACK to a lower octane the hot spots could cause pinging.

This carbon build up was actually the reason for the GM pinging problem a few years back......they actually soaked the chambers over night with some kind of solvent trying to clean the chambers.....It worked for a while untill the build-up came back.

Jul 5, 2006 | 11:40 PM

#19

DOHCmarauder

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From: Las Vegas

Quote:

Originally Posted by tdister

Not necessarily. Which reasoning do you stand behind on this statement? That it burns slower? Less energy?

Actually saw a HOT BOAT test on a low compression BBC marine engine a few years back........running at the same baseline settings, HP dropped quite a bit when running the higher octane.......the resistence to ignite is the main culprit.

That's not to say that you can't advance the timing.........but in and of itself, higher octane doesn't magically give you more power.

Last edited by DOHCmarauder; Jul 5, 2006 at 11:43 PM.

Jul 5, 2006 | 11:50 PM

#20

elite64a

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run the 87 there is no gain to the higher grade trust me I've been down that road

Jul 6, 2006 | 08:08 AM

#21

KevinM

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The fuel and spark map curves are programmed for 87, running anything higher will not provide you one once of benefit. In fact you will probably loose some performance. This is the reason why some on this board run a chip or external performance tool. When pushing the tool to high perforamce all it really is doing is overriding the Ford preprogramed spark and fuel map, using a curve that is more aggressive, hence the need to use premium fuel.

If you do use high octane fuel, and then back to 87, it will not ping since every preprogramed map only provides a controlled window, so even if the curve changes to try and take advantage of the premium which in the end it will not it is still within the parameters of 87 octane.

To many myths on this subject!

If you are getting bad gas mileage it may be due to your driving habits or you may need the updates to the PCM.

Jul 8, 2006 | 02:05 AM

#22

Rxman

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Thanks everyone for your replies...sounds like the best thing to do if I'm not running a programmer is to stay with 87 octane.

Jul 13, 2006 | 09:32 AM

#23

2004f1504X4

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This is very interesting...my truck ping or tick all times since I bought it, specially in the right side of the engin when in driver seat. fixed the knock problem tsb 06-4-7.
The dealer always answer this is normal. we don't know, 2006 have the same problem?!

But I can tell you I am running with 91 octane and lower octane is not available!

I have feeling that this engine is never normal, please help if you can!