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rotorwrench · 08-23-2017, 05:56 PM

The old flat motors were carbureted, they had old style piston rings for the most part, and they don't always have the right combination of F/A mixture for good service. If it is running rich at all, that won't help and carbs just naturally are less efficient than the modern EFI systems. Oil will turn dark slower if everything is in good working order and mixtures are within OEM specs. Rings should be fully seated in by 500 miles after O/H. It will still turn black but it will take longer. This is why they recommended frequent 2000-mile oil changes back in the day.

08-23-2017, 05:56 PM	#3
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 17,410	Re: Black oil quick The old flat motors were carbureted, they had old style piston rings for the most part, and they don't always have the right combination of F/A mixture for good service. If it is running rich at all, that won't help and carbs just naturally are less efficient than the modern EFI systems. Oil will turn dark slower if everything is in good working order and mixtures are within OEM specs. Rings should be fully seated in by 500 miles after O/H. It will still turn black but it will take longer. This is why they recommended frequent 2000-mile oil changes back in the day.