Mineral Oil and Mineral Based Oils
• Break-in procedures: RAM uses Mineral Oil.
• Normal operations: RAM uses Mineral Based Ashless Dispersant (AD) oils.

Ashless Dispersant (AD) Oil
Ashless Dispersant Oil could be written as Ashless and Dispersant Oil. There are two distinct features to remember about AD oil. Ashless stems from a requirement to clarify that the oil does not leave behind any ashes, or burning embers as it cleans. Decades ago in aviation history, oils that cleaned involved metallic cleaning particles that left embers. Such glowing metallic embers contributed to pre-ignition. Detergent oils have long since been removed from aviation piston engines. Aviation oils that clean are required to be Ashless. When an oil has Dispersant qualities, the particles created and removed by cleaning are suspended (dispersed) within the oil. Being dispersed, they are collected better by the oil filter. During the initial engine break-in period, RAM believes that AD cleansing is premature. RAM recommends a non dispersant Mineral Oil during the initial twenty-five hour break-in period of an aircraft piston engine, or replacement cylinder.

Break-in Oil
Break-in procedures should be followed whether replacing one cylinder or six, and that includes using a Multi-Viscosity Mineral Oil such as SAE 20W-50 Phillips Type-M. The minimum break-in period should be considered at least the first twenty-five hours of operation (and can continue to as much as 100 hours depending on the cylinder bore material used). The oil should be changed as soon as oil consumption stabilizes, but no later than the first twenty-five hours of operation. At that time, oil should be changed to an Ashless Dispersant (AD) Mineral Based Oil.

Should I use oil content reports?
There are a number of considerations associated with taking an oil sample as well as preparing the report, and there are a number of mechanical considerations associated with estimating engine reliability. RAM reminds aircraft operators that one report, especially one deviation from normal report, is not necessarily sufficient reason to become alarmed.

Background:
Certain parts of both Continental ( TCM ) and Lycoming engines, such as rocker shafts and piston rings, typically wear and deposit small quantities of normal wear particles in the oil.
It is a function of engine design.

The Oil Content Report Sample:
The quality of the oil sample has a great deal to do with the report. The individual taking the oil sample should use caution not to take the first oil out of the drain, because the majority of the wear metals could have settled to the bottom of the oil pan. Such a procedure could result in an erroneous reading of the metal concentration.
In addition, oil samples should only be taken from hot oil. Preferred engine warm-up should be done slowly, beginning at idle rpm for a brief period limiting idle to 1200 rpm. If a dip tube is used, it must not make contact with the bottom of the oil pan where concentrations of wear metals are likely to be exaggerated. RAM recommends engine pre-heat when the OAT is below 40°F.

How much is too much?
What is considered a high concentration of wear metal particles? Remember, an oil content report is measured in parts per million ( ppm ). Imagine a large truck filled with 1,000,000 baseballs. If 20 are flawed, they represent 20 ppm. Many engines have remained in service through TBO, even though they had one or more abnormal metal particle reports.

Recently overhauled engines:
Recently overhauled engines may have higher than normal metal particle reports; however, most laboratories are aware of these situations and usually make appropriate adjustments to their reports when so advised of the recent overhaul.

1. Aircraft should be as level as possible when checking the oil. Use the same level area
   as often as practicable when checking oil at your home airport.
   
2. Properly install the right-hand dipstick in the right-hand engine, and the left-hand dipstick in the left-hand engine. There is a difference between the two because they are calibrated to allow for the two different engine cant angles.
   
   
3. Note and mark the dipstick's top orientation after properly servicing the engine with a known quantity of oil. Maintain that orientation throughout future oil checks. Readings
   can vary by as much as 1/2 quart simply by having the dipstick's orientation 180° in error.
   
   
4. Calibrate each dipstick. Immediately after draining the oil completely, add back your normal operational quantity of oil. For example, 10 quarts. Insert the dipstick and note the oil level indicated. Often off as much as 1 or 2 quarts, the dipstick may indicate 8.5 quarts. In the future, remember that such 8.5 quarts level represents the 10 quarts level.
   
   
5. Measure oil drain-down quantity. Do so by measuring the oil quantity immediately after shut down, then again 12 hours later. Note the increased indication of oil level after the
   12 hour period -- typically due to oil draining from the oil filter, the oil cooler and the
   engine oil passages.
   
   
6. For long flights, especially over water, service the engine to its full capacity. Knowing that at full capacity some oil will be blown overboard, expect to wipe off the airframe accordingly without becoming anxious about seeing excess oil.