Black oil

[adileo]

Hi folks

Yesterday a friend and I were together at a car show. Both cars being flatheads we have a lot of good conversations. His car a 35 & mine a 39. His car has oil filter installed mine does not. His a fresh rebuild mine is not.

He asked and I always wondered....why does the oil turn black so quickly?

Thanks Andy

[19Fordy]

"Blow by" on the rings or the use of detergent oil.
I don't think the filter plays a role.

[G.M.]

I found over the years oil in flatheads becomes black fast when
they run hot. My 39 run up at 200 for a number of years and
with Skips high flow pumps, a 4 lb pressure caps it was running
at 160 so I installed Bob Shewmans 180 degree stats and both
sides run within a few degrees of 180. The engine now has over
130,000 miles, is quiet, burns no oil between changes and the
oil only gets dark yellow. I used Castrol 20/50 since start up.
This was a new NOS engine when I installed it 33 years ago. G.M.

[adileo]

Hmmm my car on the hottest day never goes over 190. Which I thought was a good operating tempature. But oil turns black after first run after oil change.

I use Rotolla 15/40

[rotorwrench]

Carbureted engines can not keep the fuel mixture any where near as stable as the modern fuel injection. There are just too many variables that they can't compensate for. Oil always turned black pretty quick on the older engines. Modern engines with electronic controls keep the oil looking cleaner for a way lot longer.

[adileo]

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Originally Posted by rotorwrench

Carbureted engines can not keep the fuel mixture any where near as stable as the modern fuel injection. There are just too many variables that they can't compensate for. Oil always turned black pretty quick on the older engines. Modern engines with electronic controls keep the oil looking cleaner for a way lot longer.

Rotor thanks that makes sense.

[OhioRick]

Run a PVC. That will help rid the engine of contaminants.