[Fot] Old Cars

[Michael Porter]

On 5/24/2020 5:05 PM, Bob Johns via Fot wrote:
> Someone was wondering when detergent oils were initiated.  I grew up 
> right down the street from the Kendall Refinery, and the addition of 
> detergents was a big deal. The detergents addition to old curded 
> engines was a problem as the curd could-would break loose and plug up 
> the oil pump screen.  Any way, as I remember the switch over was 
> 1951/1952 period.  It is hard to find non-detergent these days in the 
> better grades of oil.


The problem was not just plugging up oil screens.  Engines of the time 
used babbitted bearings, which were sealed in place with paraffin-soaked 
wicking and similar materials that became carbonized as the hot metal 
was poured.  Detergents dislodged all that carbonized material and, 
oops!, what little oil pressure such engines had went away.

Detergents were introduced when manufacturers upgraded to shell bearings 
(which were greatly refined during the war years in aircraft engines).  
Detergents tended to keep particles suspended in the oil, which 
minimized the chance of them becoming embedded in shell bearings, which 
was not so much a problem with babbitt metal.  The tin in babbitt metal 
was soft enough (and thick enough) for them to get pounded down so they 
didn't stick up much from the surface, thus minimizing the damage to 
often unhardened crankshafts.  The layer of soft metal in shell bearings 
is very thin, so the prospect of something getting stuck in them and 
being available to wear the crank required rethinking the oils used.

I suspect that the changeover to detergents was accompanied by the same 
sorts of problems that the changeover to synthetics presented.  If the 
engine is designed for the new oils, no problem.  If it wasn't, well, 
/caveat emptor /(my father, IIRC, blew up two engines in his `46 
Plymouth in the space of eight months around the time detergents became 
available).  In the late `70s, I remember reading some horror stories 
about engines converted to full synthetics that burned bearings because 
the synthetics ran out of the bearings a lot more quickly, with an 
attendant loss of oil pressure.  Around the same time, I worked with a 
guy who raced snowmobiles along with his brother.  He thought he'd try 
Mobil1, thinking he'd get another horsepower or so.  First time out, 
burned a bearing.  But, his engine had some hours on it, so they tried 
it in his brother's sled the next weekend, which had a fresh engine.  
Burned a bearing.  Engines designed for the stuff ultimately had tighter 
clearances and higher-volume pumps.  Still remember some nitwit Navy 
lieutenant screaming at me that "jet engines used synthetics," so why 
couldn't he use it in his Toyota Celica (this after complaining about 
noisy operation only after he converted to Arco Graphite, which at the 
time was something like 0W-15... in Florida, in the summertime--its hot 
viscosity was less than water).  Trying patiently to explain that it's 
fine if it's designed for that oil and pointing to the owner's manual 
just didn't work....


Cheers.

-- 


Michael Porter
Roswell, NM


Never let anyone drive you crazy when you know it's within walking distance....

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