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What is the recommendation for oil change intervals?

Paul Royko Shell Aviation AeroShell

Paul: When we’re talking about oil change intervals, no one knows better than an engine overhaul company. RAM Aircraft is a long-established engine company with a reputation for quality work and straight talk. They have had a long-standing association with AeroShell. Rick Roper is the Director of Quality for RAM.

Rick Roper

Rick: Frequent and consistent oil change intervals are one of the most critical factors in promoting engine health and longevity. But, in addition to oil change intervals, it is just as important how you change it. 

RAM recommends changing the oil and filter every 25 hours. Some operators prefer to change the oil at 25 hours and the oil filter every 50 hours. While this method is within the original manufacturer’s recommendation, consideration should be given as to why the oil is being changed in the first place. The primary purpose for changing oil is to remove contaminants. If you do not change the oil filter each time, the new oil will automatically start off with one quart of contaminated used oil. Secondly, oil filter inspection is probably the single most important tool for monitoring the health of a piston engine. So, when the oil filter is changed, it should always be cut open and inspected.

Low usage aircraft should have their oil changed every four months. When an aircraft engine sits idle, the used oil in the engine can be quite acidic which, when combined with water from the atmosphere, causes corrosion. This problem is then compounded when the rust particles that are formed, get into the oil and act like a grinding paste when the engine is next started, causing further wear and damage. By changing the oil more frequently, you reduce the chances of corrosion occurring resulting in a significantly less abrasive oil in the engine.

Finally and maybe most critical, very close attention should be paid to oil pressure coming up within 15-20 seconds on the initial start up after the oil change. Attention should always be paid to oil pressure coming up at every engine start, but especially following an oil and filter change. Aircraft piston engines are subject to oil pressure anomalies, primarily loss of prime at the oil pump. This condition is likely to occur during an oil change. Pre-oiling with a pressure pot is highly recommended. Turning the engine through with the starter (with spark plugs removed) is also an acceptable method, but use extreme caution around the moving propeller.

If oil pressure is not established in the first 15-20 seconds, abort the start. Do not attempt another start until the problem is found and corrected. Running an engine without oil pressure, even for a brief period will destroy any benefits of even the most frequent oil change intervals.

Paul: Rick, thanks for your valuable insights and for reinforcing the importance of frequent oil changes to the long-term health of aviation engines.