Conventional or synthetic
- Thread starter Chadles
- Start date
Always use a synthetic oil unless it's a racing motor. They need the resistance of a dino oil since tolerances are sloppy for speed. The loser the motor the more it can rev.. Synths are too slippery.
- Thread starter
- #3
The guy I bought the car from said he added zinc as well. Is that necessary?
That's used in the absence of leaded fuels. It's beyond my pay grade to answer that, but I'd think not.
Zinc is good to keep your nose from getting sunburn....
This is why I mix 100 low lead aviation fuel with regular to burn in my 1968 engine. It’s been liking it fine for the past 30 years. This AI response is pretty well bang on, for a change , lol.
A gas additive designed for engines originally made to run on leaded fuel is called a “lead substitute.” These additives provide valve seat protection that leaded gasoline used to offer by forming a protective barrier on the valve seats and valves, preventing valve seat recession and wear. They typically contain sodium- or phosphorus-based compounds or manganese-based compounds like MMT, which create an oxide layer during combustion to protect exhaust valves and valve seats.
Such additives are essential for older engines without hardened valve seats, as running unleaded gasoline without protection can cause valve damage, loss of compression, power loss, and poor drivability. Lead substitutes also may help reduce deposits in the intake and combustion chambers. Popular examples include Red Line Lead Substitute and various commercially available products marketed for classic cars and vintage engines.
In addition to valve seat protection, some lead substitutes also provide a mild octane boost, which is beneficial for older high-compression engines designed with leaded fuel in mind. The additives are usually mixed as fuel treatments at specified ratios (e.g., 1 oz per 10 gallons of fuel) and need to be used regularly, especially under sustained high-load or full-throttle conditions.
To summarize:
• Lead substitutes prevent valve seat recession and wear in engines designed for leaded gasoline.
• They typically use safer chemical compounds like sodium oxides or MMT instead of hazardous lead.
• They protect valves by forming a protective layer similar to lead oxides.
• Recommended for older vehicles without hardened valve seats.
• Often boost octane slightly and help reduce engine deposits.
• Frequent use ensures continuous protection, especially for high-load operation.
This type of additive is widely available and recommended for classic cars, marine engines, and farm equipment running on unleaded fuel but designed for leaded fuel protection.
Use a zinc rich oil. Amsoil has it and I think Mobil also has it. Your older engine needs the extra lubricity. Don't use synthetic. Use the search bar with the word zinc and read through what members have said over the years.
Dave91TM
Power User
Have always used synthetic in my 91 c4with no problems. I did read an article that stated the early synthetics could be hard on seals when used in vehicles from the 70's or older. Cost wise , I just wait until it goes on sale (and it always does) so it doesn't cost much more than regular oils. Just my 2 cents worth