What Is Lead Substitute and Do You Need It?

The chances are, if you drive modern car and haven’t owned classic or muscle car since the 1970’s, you’ve never even heard of Lead Substitute. If you have, you’re probably one of those classic or muscle car owners. If you still haven’t, the following article will help you gain knowledge on exactly what it does, and the history of leaded gasoline.

So, what is lead substitute anyway? Is it something that’s truly necessary, something that’s simply nice to have, or just one of those things that really isn’t all that important at all?

Why Was Leaded Fuel Used?

In the 1920’s, car manufacturers began frantically looking for a substance that could stop engine pre-detonation (knock, or pinging) and finally settled on Tetraethyllead (commonly styled tetraethyl lead), and abbreviated TEL. This lead worked to do several important things and became the standard for gasoline for half a century. It worked well, and it was the cheapest solution at the time:

  • Lead helped reduce knocks or “pinging”. Lead massively raised the octane levels of gasoline, and it needed to be once engines in the late 1950’s started to ramp up compression ratios in the never-ended horsepower race, while still operating on very primitive ignition systems.
  • Lead minimized wear and tear on the car’s valves and valve seats by reducing microwelds between the seat and the valve.

What are microwelds? The combustion chamber area is the hottest place inside the engine, as is the area near the exhaust valve, where hot exhaust gases exit. As these valves open and close, fusion between the two can happen in the form of small micro-welds, that then rip apart the moment the valve is opened again. Over time, this deteriorates the valve and the valve seat, until it can no longer seal, and a valve job must be done. Lead stopped or slowed this process by providing a barrier between the seat and the valve.

How Long Has Leaded Fuel Been Off the Market?

People first began to understand just how toxic lead really was by the middle of the 1950’s, but it wasn’t until the 1970’s and the creation of the EPA that were these dangers acted upon. In addition to the health and environmental hazards it posed, it was also found that lead didn’t gel well at all with catalytic converters and could drastically affect their function. The state of California was the first to officially decide leaded fuel was a no-go back in 1992, and once that happened, it didn’t take long at all for the rest of the country to follow in its footsteps.

It’s important to note though, that by the mid-1970’s, most vehicles were being manufactured to accommodate Unleaded fuel as the EPA phase-out of leaded gas began in the 1970’s. The main change happened in the form of valve seats that were hardened, more durable, and better able to resist the effects of the high temperatures responsible for the formation of microwelds. Unleaded gasoline no longer posed a threat to engines at all once those standards became mainstream, but even throughout the 1980’s, the common theme was which pump to use at the gas station – Regular or Unleaded?

Do You Need Lead or Substitute in an Old Car Today?

The answer to this question is a bit of raging debate, and it has more to do with the presence of hardened valve seats in the heads of any engine built prior to 1980. See, many engines of old have been rebuilt at one point or another over the course of 40-80 years. During that time, having the cylinder heads rebuilt is very common, and one of the most common upgrades done at that time is to add hardened seats into the heads. Once this is done, the need for any lead substitute of any kind is moot.

If you are unsure about whether or not your car’s engine, or heads have been rebuilt and hardened seats have been added, then decisions can be made, and even here, debate still rages. Many older classic cars are not driven much, and when they are, they aren’t driven far, or worked hard, which is why many machinists and engine rebuilders will tell you that hardened seats aren’t necessary, and simply running a lead substitute or even nothing at all but regular 93 octane will suffice just fine. Many other machinist and engine builders will insist that whether it’s a weekend cruiser or a daily driver hauling things, to put hardened seats in when you rebuild the heads.

In the meantime though, in any of these cases, lead substitute is something that can help. Keep in mind this also does not mean that failure to run a lead substitute is going to lead to disaster. As stated before, many older classic cars are not run hard, nor on long road trips or grueling work where cylinder head temps even reach the point where micro-welds could occur. Because of that, there are tons of old cars still cruising the roads, without hardened seats, running on unleaded gasoline without issue. But, if you are concerned, remember that running lead substitute isn’t going hurt – it will only help.

Is It Still Possible To Buy Leaded Fuel?

Of course, you may simply be asking: “Where can I buy leaded gas?” After all the real thing has got to be better for your classic car than a substitute, right? To answer that question: you’re not going to be able to roll up to a gas station and buy leaded gas anymore. Technically speaking, it does still exist and is permitted in specific types of vehicles (like aircraft or farm vehicles, to name two examples). It’s no longer legal to put leaded gas in your car though, whether it’s a classic or not.

Don’t even think about trying to do it on the downlow either. If you’re found to be driving a car with leaded gas in the tank, you could well wind up slapped with a hefty $10,000 fine for your ingenuity. In other words, lead substitute is really the only acceptable alternative.

In conclusion, if you’re really passionate about classic cars, lead fuel additive is definitely a good thing to know about and consider. It probably isn’t essential for most vehicles, but it definitely isn’t going to do any harm and can help some older engines prevent premature valve issues. Ultimately, it’s up to you. You can get the parts you need at your local AutoZone Store. If the job is too big for you, seek out one of our Preferred Shops to help you do the job.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

FREE Loan-A-Tool® program requires returnable deposit. Please note that the tool that you receive after placing an online order may be in a used but operable condition due to the nature of the Loan-A-Tool® program.

Related Posts