Get the lead out.

Does lead occur naturally in gasoline? If so, how is it removed to meet todays unleaded requirements? If not, why was it added in the first place? And if it was added (for increased octane, maybe?), what has taken its place?

Tetraethyl lead used to be added to gasoline to boost the octane, which it did very well. No substitute has been found which raises the octane as economically, which is why unleaded used to cost more than regular when you could by (leaded) regular. Lead does not naturally occur in petroleum.

There are other substances which raise the octane rating of gasoline. One in common use is ethanol, which also adds a little extra oxygen to the mix and makes things burn cleaner. Unfortunately it can be corrosive to some rubbers and related compounds which are found in automobile engines. Manufacturers now use alternate compounds which don’t react to ethanol but it can cause problems in older cars.

BTW, a high octane rating allows the engine to run at a higher compression ratio, which is also more efficient. Specifically the higher octane rating prevents “pre-ignition” or knocking. It doesn’t affect performance directly. Today’s engines are designed with lower compression ratios since the ratio is also an important factor in pollution control, so the very high octane gasolines of the past are no longer needed or available. If your engine pings or knocks, switch to a higher octane gasoline, otherwise save your money and buy the cheaper stuff. It’s all unleaded nowadays.

“If you had manifested fatigue upon noticing that you had been an ass, that would have been logical, that would have been rational; whereas it seems to me that to manifest surprise was to be again an ass.”
Mark Twain
Personal Recollections of Joan of Arc

Lead was added to protect the valves. These days they have much better valves. So, back to unleaded. Why unleaded cost more than leaded at the time is a mystery.

Valve guides actually. However lubrication of the guides was a secondary benefit. Octane boosting was the primary reason. Materials themselves were not significantly inferior 30 years ago, but manufacturers could use cheaper materials w/ lead present. So they did.

I am involved in an environmental case right now that involves lead contamination. My expert industrial hygienist (sp?) tells me that the toxic effects of lead were known at least as early as Hippocrates, who wrote about them in 350 B.C. or so. Makes you wonder why they put lead in the gasoline in the first place, instead of trying to come up with a substitute.


Because crappy gasoline with tetraethyl lead added to it burns like the good stuff and costs less.

John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams