FAA Aviation Mechanic Powerplant (AMP)Engine InspectionMedium
An engine's oil consumption records show that 3 quarts of oil were added over a 25-hour flight period. The manufacturer's service limit for acceptable oil consumption is 1 quart per 10 hours. Based on this trend, is the engine's oil consumption within limits?
- ANo, because any oil addition indicates excessive consumption
- BYes, the consumption rate of 1 quart per 8.3 hours is within the limit
- CYes, because 3 quarts over 25 hours is less than the 10-hour limit
- DNo, the consumption rate of 1 quart per 8.3 hours exceeds the 1 quart per 10-hour limit
Show answer & explanationAnswer & explanation
Correct answer: D. No, the consumption rate of 1 quart per 8.3 hours exceeds the 1 quart per 10-hour limit
Dividing 25 hours by 3 quarts gives a consumption rate of one quart every 8.3 hours (25/3 = 8.33), which is faster (worse) than the allowable 1 quart per 10 hours, meaning the engine exceeds the manufacturer's oil consumption limit.
Why the other options are wrong
- A. Some oil consumption is normal; the limit is a rate, not a zero-tolerance standard.
- B. Incorrect—8.3 hours per quart is a faster consumption rate than the 10-hour limit, not within it.
- C. This misreads the comparison; the actual rate must be calculated and compared per quart.
Oil Consumption Trend Monitoring
Oil consumption is tracked as a rate (quarts per flight hour) and compared against the manufacturer's published limit to detect developing engine wear.
- Rate = hours flown ÷ quarts added
- Rising consumption trend can indicate ring, valve guide, or seal wear
- Compared against manufacturer TCDS or service manual limits
- Used alongside compression tests and oil analysis for engine health monitoring
Memory trick: 'Divide Hours by Quarts to Judge the Squirts' — calculate the rate before judging.