Engine Oil Change Interval & Soot Levels | Technical Service Bulletins
Engine Oil: Technical Service Bulletins
Engine - Oil Change Interval and Soot Levels
Article No. 86-10-14
OIL - ENGINE (6.9L) - CHANGE INTERVAL AND SOOT LEVELS
LIGHT TRUCK 1983-86 E, F SERIES
The 6.9L Diesel engine requires different engine oils and oil change intervals than other Ford gasoline engines. Due to requests for a technical method of
determining oil change intervals in the field, the following information is provided.
Use of an engine oil of correct quality and proper viscosity and following recommended oil change intervals are essential to good engine starting,
performance, oil consumption, and long-term engine durability. Depletion of the lube oil additive package and soot formation are the major limiting
factors to the useful life of the lube oil.
As the engine is operated, the additive package breaks down and at the time the minimum acceptable level of additive is remaining, an oil change is
required. When the additive package reaches the minimum acceptable level and the lube oil is not changed, the engine wear and deposits rapidly increase
and can result in increased oil consumption and shortened engine life. Breakdown or depletion of the lube oil additive package is a function of vehicle
service.
In all diesel engines, soot is formed as the fuel burns. Some of this soot gets past the piston rings into the oil. Severe operating conditions, such as
prolonged idling or lugging can increase soot formation as can operating a sea-level calibration at high altitude. Soot is measured as insolubles or
Coagulated Pentane Insolubles (CPI) through used lube oil analysis programs. 3% CPI is the acceptable limit. CPI levels above 3% are unacceptable.
If CPI levels above 3% are indicated the oil change interval should be reduced. Never use values lower than 3% CPI to extend oil-change intervals
beyond 5000 miles (8000 km) as costly engine damage can result. The ability of an engine oil to suspend this soot and keep it from settling out as sludge,
or clogging oil filters is called "dispersancy". This dispersancy ability varies among API SF/CD quality oils. Oils with improved dispersancy reduce the
effect of soot build-up and tend to reduce engine wear.
To obtain maximum engine life and improve cold starting, use oils meeting both API categories (i.e., SF/CD). Do not use oils labeled as only SF or only
CD, as they could cause piston ring sticking or excessive
valve train wear. Ford's Motorcraft Super Duty 15W40 SF/CD engine oil (green can) meets the lubrication requirements of the 6.9L diesel engine
including beneficial qualities not yet covered by API classification that improve dispersancy.
CPI levels can be useful in identifying severe duty usage. However, severe duty usage is also defined as:
Trailer towing for long distances (over 1000/1600 km), sustained high speed driving at GVWR during hot weather (over 90~F/32~C), frequent or
extended idling (over 10 minutes per hour of normal driving), operation in severe dust conditions, or frequent short trips (10 miles/16 km or less) during
freezing weather.
Severe Duty Usage oil change interval should be 2500 miles (4000 km) while Normal Duty Usage oil change interval should be 5000 miles (8000 km) or
6 months.
OTHER APPLICABLE ARTICLES: 85-25-19, 85-25-18, 85-7-16, 84-1-13, 83-23-15
WARRANTY STATUS: "INFORMATION ONLY"
