True...but the reason is it's illegal to operate a motor vehicle on leaded fuel on US highways these days, courtesy of the EPA.mjewell said:but just try to find a leaded fuel anywhere. the only place you can still get it is at a ractrack,
Not if the slightest amount of detonation begins to occur - and retarding the spark to prevent that will push the emissions up through the roof!bosco said:would 87 octane run cleaner than 91 octane......in an emissions test environment?
Emissions testing generally measures three things; Nitrides of Oxygen (NOX), Unburned hydrocarbons (HC's) and Carbon Monoxide (CO). All other things equal (in the absence of detonation, more about that in a moment), NOX goes UP with more advanced ignition, due to higher combustion temperatures, if I recall the basic engine theory that they tried to jam into my head in "Internal Combustion Engines: Theory and Practise" during a very hectic third year of Engineering. Unburned HC's go the other way, while CO has more to due with mixture. The curves relating to HC/NOS and CO are all a bit contrary to each other wrt to mixture, which is why three way catalysts and lambda-sonde O2 sensors with highly accurate fuel mixture feedback control is the norm is modern fuel systems. Well, they ALL are more affected by mixture, but let's stick with the issue of octane and ignition advance.GTJIM said:Not if the slightest amount of detonation begins to occur - and retarding the spark to prevent that will push the emissions up through the roof!