How often to get an oil change on a C-172?
USAFisnumber1
The oil collects soot, water and small particles of metal. Adding oil over and over does nothing to remove that stuff. Eventually the filter will gum up and the oil will not get where it needs to go. The reason you change the oil is to dump out all the garbage completely. You put on a new filter too as the old one has garbage in it too. That A&P mechanic is an idiot.
lowlevel
Every 50 hours for those with an oil filter, or every 25 hours with a screen. Also every 12 months if you fly less than that and perhaps every 6 months for seasonal grades or in areas of high moisture. The “progressive oil change” can be done. There’s a plane hanging in McCarran airport that was airborne continuously for over two months without an oil change (over 1500 hours... the entire TBO of the engine). But not with any guarantee of reliability. Oil is the cheapest form of preventative maintenance you can do to the aircraft.
Anonymous
That’s fine reasoning for a car where engine failure just leaves you broken down safely on the ground. It’s poor advice for any aero-engine. Unless you change the oil you cannot get a sample tested to check for excessive engine wear. You also cannot look for visible metal particles as you strain the used oil. Compared to the overall cost of flying, skimping on oil changes is a dangerous false economy. A lost quart every couple of flights sounds excessive but it also depends upon how many hours each flight is for, but it’s certainly less than ideal so I’d personally wish to get the cause diagnosed and fixed and until then I’d insist on more frequent oil examinations so would err towards every 25 hours.
Bertsta
Regardless if you are topping up, the oil needs to be changed so you flush out any cr@p in the motor. I can't comment on intervals but more is always better.
duck you sucker!
Is this the Same "mechanic" who told you it was ok to WD-40 a starter bendix? Many Do, but Not kosher. I am taught in class the FAA way to do things so we can COA's and leave a paper trail of complicity. You don't give year or if you have an Oil Filter.. This 25 is a default if No filter. 50 hrs, If filter. Either case, at least every 4 months. And, this also varies by frequent or occasional use: https://generalaviationnews.com/2004/12/24/the-no-1-question-of-oil-experts-how-often-should-oil-be-changed/ Oil is (relatively) cheap; engines are Not. My teachers say this " adding a quart and negating a proper change" philosophy Still leaves dirty oil in. It is only partially valid with a cage, where an engine failure on the road probably won't kill a pilot and 3 passengers. Like, my leaky Toyota.
Anonymous
All aircraft have a maintenance schedule. Determine what the schedule is from the aircraft service manual to change to the oil and follow it. We are just guessing here and we will not find it for you.
vic
every 3000 miles or every 3 months whichever comes first