The world of aviation maintenance evolves, and even standards established for decades can receive important updates. The Pennsylvania engine manufacturer published a major revision to its engine-oil instructions, replacing guidance that dated back to 1995. The update applied to its horizontally opposed engines.
To read the complete technical column and the reference tables in Magazine Aviation, click here: https://magazines.smmedias.ca/V24N5/16/
Although a Service Instruction does not carry the same mandatory status as a service bulletin, its content remains important to engine health. Here is a summary of the key points presented in the article for aircraft owners and operators.
Choosing the right type of oil
Oil selection should not be random; it should reflect outside ambient temperature. The guidance cited in the article explains the relationships among SAE, commercial and military grades.
It is important to distinguish between the two main categories identified:
- Non-dispersant oils.
- Ashless-dispersant oils.
The emphasis is on sound judgment and adapting to climatic conditions, particularly during the critical engine break-in period.
Lubrication in operation and during break-in
The break-in rules presented in the article are strict: all turbocharged engines must be broken in and then operated using ashless-dispersant oil only. For other series, such as the O-320-H or O/LO-360-E, either non-dispersant mineral oil or ashless-dispersant oil may be used from the start.
One specific point concerns Lycoming additive LW-16702. The article states that it is to be added at the initial fill and then every 50 hours or at each oil change. It also notes that using ashless-dispersant oil from the beginning of break-in may extend the break-in period.
The challenge of transitioning between oils
Converting an engine from mineral oil to dispersant oil after several hundred hours of operation carries risks. An abrupt change can loosen accumulated deposits, creating a risk that oil passages could become obstructed.
If this transition is required, the article presents a three-step method attributed to Lycoming:
- Complete drain of the mineral oil before switching to dispersant oil.
- Short first cycle: do not operate the engine for more than five hours before the next oil change.
- Increased monitoring: inspect filters and screens every 10 hours until they remain completely clean.
A warning about additives
The instruction discussed in the article ends with a serious warning about unapproved additives, such as detergents or compounds described as “top cylinder lubricant.” It reports Lycoming’s warning about the potentially harmful effects of these products, as well as the use of automotive oil, which the article describes as prohibited.
These recommendations are specific to Lycoming. The original French article suggested that some principles may sometimes be relevant to other engines such as Continental or Franklin, but the applicable manufacturer’s current instructions must always be consulted for the specific engine and configuration.