moto_italia

Call me old school (or just old), but I was always told that unless oil temperatures periodically exceeded 212 degrees (F), water inside the engine from sources such as condensation would fail to evaporate, and ultimately cause problems. So, I always smile when I see 215 degrees on my oil temperature gauge. :-)

Here's a little article about what sludge is, and how sludge forms in an engine, sometimes as a result of failure of the oil to ever exceed 212 degrees:

Sludge in gasoline engines is usually black emulsion of water and other combustion by-products, and oil formed primarily during low-temperature engine operation. Sludge is typically soft, but can polymerize to very hard substance. It plugs oil lines and screens, and accelerates wear of engine parts. Sludge deposits can be controlled with a dispersant additive that keeps the sludge constituents finely suspended in the oil.
"Black Sludge" is defined as thick to solid material with low water content, of dark color, light oil insolubles, and typically found in rocker cover, cylinder head, timing chain cover, oil sump, oil pump screen, and oil rings in variable quantities.
Sludge in diesel engines, is soot combined with other combustion by-products which can thicken the oil to gel like sludge. This sludge is typically soft, but can also polymerize to very hard substance. It plugs oil filters, oil lines and screens, and accelerates wear of engine parts.

What causes "sludge"?
Sludge formation is the result of one or more of these factors:
- severe service driving with improper drain intervals

- mechanical malfunctions

- inadequate engine maintenance


Severe Service Driving:
The term “severe service” refers to:


1.) Short Trips - Engine Coolant and Engine Oil never reach the "normal" operating temperatures (170º F to 190º F for coolant and over 212º F for motor oil)
2.) Stop & Go Driving

 - Slow driving speeds and long idling periods lead to high under hood temperatures due to limited air flow
- The "average" miles per hour run time is low and engines accumulate many engine run hours for the relatively low number of miles driven, thus typically exceeding the safe number of hours for which particular motor oil was designed to operate ( Typically service life of premium motor oils is not more than 212 hours )

3.) Extended Idling

- sitting in traffic

- delivery truck operation
- The "average" miles per hour run time is low and engines accumulate many engine run hours for the relatively low number of miles driven, thus typically exceeding the safe number of hours for which particular motor oil was designed to operate ( Typically service life of premium motor oils is not more than 212 hours )

4.) High temperature operation
- driving at high ambient temperatures
- towing
- driving at maximum engine power output (high speeds or up hill)


5.) Extreme Cold
- starting engine below 0º F
- Engine Coolant and Engine Oil never reach "normal" operating temperatures 
 (170º F to 190º F for coolant and over 212º F for motor oil)

6.) Heavy Loads

 - operating in hilly regions

 - trailer Towing
- oxidation rate of conventional motor oils doubles for every increase of 15º F to 18º F, therefore motor oil that is fine for thoushands of miles at "normal" operating temperature can fail in just few hours if it is overheated to over 300 F.

__________________
Kevin