Gas?

[kevdc77]

I've got the 4.6 V8 and was wondering which octane to use? The manual says 87, but is that right? I was always under the impression that the larger the engine the higher the octane!!

 

[EasyRhino]

The higher the compression ratio, the higher the octane. Not engine displacement. Use what the owner's manual says. Paying for higher octane does not make engines run better, it just makes money run through the wallet quicker.

Remember that the higher the octane (the whole point of octane), the slower the gas charge in the combustion chamber burns.

 

[nascar_intimid]

higher octane also plugs up the cat.....

 

[aldive]

higher octane also plugs up the cat.....

Say what?

 

[EasyRhino]

higher octane also plugs up the cat.....

I had not heard this item.. Please do tell more.

 

[E.B. Cornburner]

higher octane also plugs up the cat.....

Impossible. The fuel's octane rating is only a measure of its resistance to pre-ignition (detonation, or pinging), not anything else. The amount of heat energy in premium vs. regular gasoline is identical.

Only way a higher octane fuel could ever possibly plug a catalyst is certain unscrupulous fuel blenders were adding methylcyclopentadienyl manganese tricarbonyl (MMT) to the fuel as a cheap octane booster. The manganese components would coat the spark plugs, O2 sensors, and catalyst substrates rendering them useless if a high enough concentration was present. I'd never heard of MMT actually plugging a catalyst, but I suppose it's possible if it were grossly over-used. That, or if the plugs got coated to the point where misfires occurred, the cat could overheat and melt down from the excess unburnt fuel entering it.

MMT is no longer used as an octane booster in pump gasoline in the US or Canada (Canada abolished it much later though) anymore, though it can still be found in certain off-the-shelf octane booster fuel additives. Most of which say right on the bottle that it's not to be used in vehicles with catalytic convertors.