Question about Octane

yh8t · Mar 18, 2009

My motor is a 92 5.0 HO. Is there a benefit in pumping the higher octane? is there really a difference?

JMP · Mar 18, 2009

There is a difference, it depends on your compression. Higher compression the engine is, the higher the octane is needed.

If the engine calls for it, its best to use it.

cracker · Mar 18, 2009

If your vehicle runs fine on regular gas, then there is no benefit in running higher octane. Higher compression engines need the benefit to keep from pinging.

Bundy · Mar 18, 2009

i have the same motor and i put 91 in- it's really not that much more for the assurance you tried to put the better gas in- LOL

68ford · Mar 18, 2009

higher octane pump gasoline only has a higher flash point. it can withstand higher heat/pressure without detonating.

it does not have any more thermal energy within it.
if you advance your timing you may see a little power increase and little better mpg.

but if your engine has a carb on it and you just put in premium, you will make less power.

91 will burn colder, releasing less heat/energy when used in an application where 87 can be used.

newer engines with computer controls where things may adjust due to less knock or something, then yes you may notice a difference.

high actane gas in a low compression application is more likely to have deposits and unburned hydrocarbons left behind like on valves and introduced to the oil which creates acid.
similar effects as running too low of coolant temp along with low compression.

yh8t · Mar 18, 2009

Damn u guys are smart. Thanks for the input. This is a cool forum.

Broncobowsher · Mar 18, 2009

Engines run best and most efficient on the lowest octane possible that still is sufficent to prevent detonation. Most cases it is 87 with a stock engine. If you start bumping cylinder pressure (more compression, different cam timing with earlier intake valve closing, or something as simple as advancing the timing) then you may need more octane. Also an engine with a hot spot in a chamber or piston that can act as a glowplug can sometimes benifit from higher octane so that hot edge isn't enough to light the mix.

hose101 · Mar 19, 2009

What did the motor come out of? Just look up the recommended octane from the manufacturer and you have your answer. Has the motor been built up at all. That may change your needs.

yh8t · Mar 19, 2009

hose101 said:
What did the motor come out of? Just look up the recommended octane from the manufacturer and you have your answer. Has the motor been built up at all. That may change your needs.

From a 92 Mustang 5.0 it was rebuilt 4500 miles ago. not built up it is fuel injected. Ive always put 91 but then tried 87 and cant tell the difference. My Shelby is programed for higher octane and has only run on 100 since new. But I know that car is different.

Question about Octane

yh8t

New Member

JMP

Full Member

cracker

Bronco Guru

Bundy

Bronco Guru

68ford

Bronco Guru

yh8t

New Member

Broncobowsher

Total hack

hose101

Full Member

yh8t

New Member

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