Should I be running with lead additive, or just higher octane? I noticed it was knocking a bit on accel, and switched to 89 octane, and it has quit substantially, almost never does it anymore. Would adding lead additive to it change this ? I'm not sure if I should be using it because afaik 69 was the changeover year. How can I tell ?


Cheers,
Jake

I'm not sure about using leaded gas in your car.

You would only use high octane in your car if it requires it. The compression ratio of you engine would determine the use of high octane fuel. Some of the more techie guys should be able to answer your question better than I.

Some Info I found


Lead

The mixture known as gasoline, when used in high compression (http://en.wikipedia.org/wiki/Physical_compression) internal combustion engines, has a tendency to autoignite(detonation) causing a damaging "engine knocking (http://en.wikipedia.org/wiki/Engine_knocking)" (also called "pinging" or "pinking") noise. Early research into this effect was led by A.H. Gibson and Harry Ricardo (http://en.wikipedia.org/wiki/Harry_Ricardo) in England and Thomas Midgley (http://en.wikipedia.org/wiki/Thomas_Midgley) and Thomas Boyd in the United States. The discovery that lead (http://en.wikipedia.org/wiki/Lead) additives modified this behavior led to the widespread adoption of the practice in the 1920s and therefore more powerful higher compression engines. The most popular additive was tetra-ethyl lead (http://en.wikipedia.org/wiki/Tetra-ethyl_lead). However, with the discovery of the environmental and health damage caused by the lead, and the incompatibility of lead with catalytic converters (http://en.wikipedia.org/wiki/Catalytic_converter) found on virtually all newly sold US automobiles since 1975, this practice began to wane (encouraged by many governments introducing differential tax rates) in the 1980s. Most countries are phasing out leaded fuel; different additives have replaced the lead compounds. The most popular additives include aromatic hydrocarbons (http://en.wikipedia.org/wiki/Aromatic_hydrocarbon), ethers (http://en.wikipedia.org/wiki/Ether) and alcohol (http://en.wikipedia.org/wiki/Alcohol_as_a_fuel) (usually ethanol (http://en.wikipedia.org/wiki/Ethanol) or methanol (http://en.wikipedia.org/wiki/Methanol)).
In the U.S., where lead was blended with gasoline (primarily to boost octane levels) since the early 1920s, standards to phase out leaded gasoline were first implemented in 1973. In 1995, leaded fuel accounted for only 0.6 % of total gasoline sales and less than 2,000 tons of lead per year. From January 1 (http://en.wikipedia.org/wiki/January_1), 1996 (http://en.wikipedia.org/wiki/1996), the Clean Air Act (http://en.wikipedia.org/wiki/Clean_Air_Act) banned the sale of leaded fuel for use in on-road vehicles. Possession and use of leaded gasoline in a regular on-road vehicle now carries a maximum $10,000 fine in the United States. However, fuel containing lead may continue to be sold for off-road uses, including aircraft, racing cars, farm equipment, and marine engines.[12] (http://en.wikipedia.org/wiki/Gasoline#cite_note-11) The ban on leaded gasoline led to thousands of tons of lead not being released in the air by automobiles. Similar bans in other countries have resulted in lowering levels of lead in people's bloodstreams (http://en.wikipedia.org/wiki/Blood).[13] (http://en.wikipedia.org/wiki/Gasoline#cite_note-12)[14] (http://en.wikipedia.org/wiki/Gasoline#cite_note-13)
A side effect of the lead additives was protection of the valve (http://en.wikipedia.org/wiki/Poppet_valve) seats from erosion. Many classic cars (http://en.wikipedia.org/wiki/Classic_car)' engines have needed modification to use lead-free fuels since leaded fuels became unavailable. However, "Lead substitute" products are also produced and can sometimes be found at auto parts stores.
Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improve combustion (http://en.wikipedia.org/wiki/Combustion), and to allow easier starting in cold climates.
In some parts of South America (http://en.wikipedia.org/wiki/South_America), Asia (http://en.wikipedia.org/wiki/Asia), Eastern Europe (http://en.wikipedia.org/wiki/Europe) and the Middle East (http://en.wikipedia.org/wiki/Middle_East), leaded gasoline is still in use. Leaded gasoline was phased out in sub-Saharan Africa (http://en.wikipedia.org/wiki/Sub-Saharan_Africa) effective 1 January (http://en.wikipedia.org/wiki/January_1) 2006 (http://en.wikipedia.org/wiki/2006). A growing number of countries have drawn up plans to ban leaded gasoline in the near future.

I suggest you ask the guys in the motor section of this forum, particularly the 500, 472, 425, 368 (http://www.cadillacforums.com/forums/500-472-425-368/) thread. Good luck!

Greg

You don't need lead additives, unless you are doing a lot of full throttle, hard acceleration, towing, or very high speed/RPM highway use. You DO need high octane in that engine, though! 91, or better if you can get 93. GM went low compression across the board in 71. I use 87 in my 71, but use 91 in my 65.

That old 472 doesn't have hardened valve seats unless someone upgraded them. If you plan to keep it forever you should use some kind of lead or lead substitute. This is one car that actually need premium fuel too.