Marvel mystery oil used as a lead substitute?
Exactly.....but the fact is, you CAN drive the car as much as you want. What dictates hardened seats is exhaust temperature. Your car is so light, the exhaust will never be hot enough to warrant hardened seats. But you cannot tell people that no matter how much you preach it. Our light cars with good cooling systems and decent gears just don't generate enough exhaust heat to worry about.
This is 100% correct.
I have driven thousands of miles on these old engines over the years and never had a problem with the valves being affected by the lack of lead in the gasoline.
Never.
My main concern nowadays would be the content of the ethanol in regular gas which could cause a lot of problems with the old rubber hoses, carb parts, and the fuel system in general by eating away at it.
That's why I use only mid grade or premium on my cars depending on the compression ratio.
It's better to be safe than sorry.
For a low compression 318, I would use mid grade and I have with good results.
On my 10:1/2 to one 340 I use Shell premium and have no issues such as pinging, running on when shut off, etc.
Chevron is great gas here in Canada, and so is Shell.
Regular gas has 10% or more ethanol in it and premium has a minimum of 0 to 5% up here.
I have always had good luck with Shell, but we don't get Chevron in the area where I live or else I would buy that brand.
The true test that I've found is how long does it take for the gas to evaporate out of the carb?
If it's a week or more, it's good gas.
If it's one or two days, you have a lousy brand of regular.
And as a side note, the places in Canada that have the good Shell gas is Shell (of course), Costco, and Canadian Tire.
Stay away from Esso, Fast Gas, or other low name places.
Petro Canada is okay, but not as good as Shell and Chevron.
I'm not sure of U.S. brands.
I hope this helps you...