I was wondering about leaded gas. Will it run in a car only for unleaded (legality notwithstanding)? What was different about engines that ran on leaded fuel? Why could leaded fuel run such high octane cheaply in comparison to unleaded fuel? What would running leaded fuel in an unleaded engine do, and vice versa? Just a stream of conciousness curiosity. Thanks.
Matt

 

leaded gas will destroy your cat rendering your emmisions system inoperative. If you dont have any emmmisions equip., run it if you can. Leaded additaves prevent knock better then the conventional anti-knock additaves.

 

Cars built after 1976 don't need leaded fuel. The lead was added to increase valve seat life and increase the octane. After 1976 all factory heads have hardened seats so they didn't need leaded fuel.

Leaded fuel now is only used in race engines with higher compression ratios. The lead increases the octane which will resist detonation with high compression or power adders.

Leaded fuel will run fine in an engine built for unleaded fuel HOWEVER the lead will kill the O2 sensor and plug the catalytic converter.

 

As Stephen says, leaded fuel made for cooler exhaust temperatures. Therefore softer valve seats.

If your car is not meant to run leaded fuel (for the reasons posted above), then running it will not get you much.

Basically, it was a cheap way to make good gas, that was resistant to detonating.

 

How did leaded fuel raise octane? I thought higher octane was obtained by removing impurities? What does unleaded fuel do to older valve seats? Melt them? Was the lead added to the gas or was it simply not taken out? Thanks.
Matt

 

The motors were not different, the valve seats were.
a motor deighned for leaded fuel will usually run on unleaded cuz over the years the valves have a lead build up on them, however, it is not reccomended.
an unleaded motor will run on leaded, but if eqipped with a cat., it will destroy it.
the lead was added, it is not just regular lead, it is a lead based chemical called Tetraethyl Lead.
The lead had no effect on octane whatsover. Back in the day of muscle cars, the engines ran much higher compression, 11:1 was common, so the fuel needed to have higher octane, which is more resistance to knock, becuz it does not burn as fast.

Also, the method of rating octanes has changed over the years, they now use the R/M method: Research Octane and Motor Octane. I may be wrong about this, but I belive the Research Octane was what the fuel rated at under labratory conditions, and the Motor Octane is how the fuel reacted when burning in a motor.
Back in the day, it was just the research, which is always higher than the motor.
the R/M devides the research and the test, to get the average.

In short, todays 93 octane is probably equal to the 60s 100 octane.

belive it or not,the higher the octane, the less refining the gas goes through, then they actually charge you more at the pump!!

 

So what would a lead additive do for the cars? You can buy the substitute. Would that help any?

 

Leaded fuels DID NOT raise the octane of the fuel. They DID help resist detonation, tho.

Octane is an actual chemical, which is what we rely on for resistance to detonation.

A lot of people have trouble wrapping their heads around the fact that Octane is an actual chemical additive, and not a simple numerical RATING of detonation resistance.
The amount of Octane, and the resistance to detonation is a direct relation, tho.

Having higher octane fuel IS NOT related to removing impurities.

Yes, unleaded fuel damages exhaust seats that weren't meant for it. Most exhaust seats made for unleaded fuel were either; replaced with ones for leaded, damaged because owners were too cheap to replace them, or the owner used lead additives that could be bought at parts stores to help the car along.

88Bravo: AGAIN, lead will not help a car that is not meant for it. If you do have a car with leaded exhaust seats, then yes, a lead additive will help.

The main reason that leaded fuel stopped getting sold for regular use was because of the damage to the environment.

 

Good point, Josh, I had never thought about that.

 

Is the chemical octane expensive? I think i've managed to wrap my head around the fact that octane is in fact a chemical. Is it added or found naturally in crude oil? If its not expensive could i buy Regular gas and just add some octane? Maybe get a chemistry set an make it? Im still in the dark about what exactly happens to the soft valve seats when they get get hot exhaust temps. Do they actually melt and have the valves fuze to them? Doesnt slower burning fuel hurt power? I thought the faster the flame front travelled from the spark plug, the more power was made? I guess right about now im talkin outta my ***, so i'll quit. Thanks
Matt

 

If you run unleaded fuel in an engine with Soft Valve seats ( that is supposed to run Leaded fuel) the valve seats will crack or otherwise be damaged over a period of time.