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I have known people who have never changed the oil in their mower, and others who do it twice a year. How often do you guys change the oil in your lawnmower?
I changed the oil in a riding mower I bought used.
Apart from that, I have never changed the oil in a mower.
Never. I changed the oil once in my pressure washer and the damn thing never worked again.
I currently have an electric mower, no oil required.
Is that in 10, 20, or 40 years? How long do your mowers last?
Probably every other year. I’d like to do it each year at the end of the season, but when I pull the dipstick out and it doesn’t look that dirty, sometimes I don’t really feel like going through all the work when it’s starting to get cold out.
My snowblower, on the other hand, I’m pretty good about changing the oil on (as well as most of the other seasonal maintenance) each year, again, at the end of the season. Of course, having a broken snow blower is a bigger deal than a broken lawn mower. Both because snow removal has to be done sooner which means fixing it in the freezing cold, running out and buying a new one with not a lot of time to think or at the very least shoveling to buy some time. Also, it’s a lot easier to change the oil, run the gas out and do some other maintenance in spring on a warm day on a snow blower than it is to do similar things to a lawn mower on a cold day, especially if you usually get home from work after dark.
I changed it once in 10 years, Along with the snowblower and generator oil. Usually after the first year as these usually don’t have oil filters and I want to get anything related to engine break-in cleared out.
Hey if a car can go 7500 miles between oil changes these things should go several generations without oil changes.
Although I do check the oil almost before every use (I lost a snowblower from lack of this). The oil still looks good and not used.
I have a bunch of things with small engines: garden tractor, tiller, push mower, go-kart, generator, and a couple mini-bikes. I change the oil in each engine once a year, usually in the spring. I use 10W-30 synthetic in each.
I’m lazy. I change it once before the season in the spring and then top off as necessary during the summer.
I saw a pretty little electric oil-drainer pump yesterday, presumably for autos, £12 each. I had no idea such things existed. I thought one just undid a nut and let gravity do it’s thing.
The one I bought used lasted about 3 seasons. Transmission was going out when I got it and finally gave up. I changed everything changeable on it when I acquired it, though.
Push mower I had at the time, I used for too much brush clearing a fence line and it quit running. My bad. It was a cheapo to begin with.
Rider I bought to replace the first one lasted beautifully for a couple years until I sold it to move. I did change the plug and air and fuel filter on that one each year.
Current self propelled push mower is 5 years old and a freaking champ.
So, never had the opportunity to own one for 30 years, sorry.
Never.
When I bought my first house, times were different. Specifically, they were times when you could get a brontosaurus to graze on your lawn to keep it trim. Instead, I bought a two-cycle Lawn Boy. No oil change, you just added oil to the gas. That two-cycle Lawn Boy lasted me most of my adult life. When it finally got very sick I nursed it back to health with a new spark plug, and then cleaning the spark plug every season, and then every month, and then eventually it was hopeless. It just couldn’t start any more. So I took the poor thing in to Home Depot when the gubbermint was offering great rebates to anyone turning in a gas lawnmower, working or not, in exchange for an electric one.
So I said a tearful goodbye to the faithful old Lawn Boy and toddled off with an electric mower, practically free. So no, I’ve never changed the oil on a lawn mower, and the great and, I’m sure, worthy companies that manufacture lawn mowers have never really made a lot of money from me. 
Before I went to mostly hand and electric my usual was to start the season on fresh oil.
Every tank of fuel 
I still have the '76 LawnBoy model my parents had. Lightweight (magnesium deck) and simple.
A car goes 10,000 miles between oil changes, it also has an oil filter, regardless that doesn’t mean your lawnmower can. Every other season sounds reasonable. If they have an hour based recommendation, that would be good to follow. Snoblowers often don’t have air filters, apparently the thought is the air is a lot cleaner in the wintertime.
Once a year for the 12-year-old lawn tractor. I mow a lot of areas around my house and garden areas several times each season, so it needs to run. It also hauls loads of manure from the barn and pasture to the garden, and limbs/debris to the burn pile. Sometimes I use it to drive up tracks into my forestry and see how things are going at the far corners of the property. I’ve even used it to drag dead livestock to an area more accessible for my deceased animal removal folks to get to.
In short, it gets a lot of use each season (fortunately rarely for the deceased livestock).
My dealer sends a guy out to do a service call and he changes the oil and filter, air filter, replaces the spark plug if needed, checks the belts, sharpens the blades and keeps the little tractor in good shape. Way cheaper than buying a new one.
Close to never. I’ve changed other folk’s lawnmower oil more than my own.
I’ve only owned used, second/third-hand mowers. If I ever spent my hard-earned money for a new one, I’m sure I’d change the oil every season or so. Currently, I pay a local business to do my mowing for me. Gives me time to change the engine oil in all my 2-strokes! 
Every 25 hours … or about once a month during Spring … every other month the rest of the year … that’s a lot of mowing and a cheap-o John Deere rider lasts about 8 to 10 years …
Never.
Our lawn mowers get used hard and put away wet. With some spray starter they start right up in the spring, even though they have the same tank of gas from the previous season. They are still running when the body rusts out and they are sent to mower heaven.
ETA: the diesel Kubota lawn tractor gets regular maintenance, including a yearly oil change, but I wouldn’t call it a “lawnmower”.
I have a yard king mower I bought new in 2002. I mow my yard about 12-16 times during the spring/summer/fall.
I’ve never changed the oil and I’ve never sharpened the blade. I’ve topped the oil off but that’s it. It runs/cuts beautifully.
I’ve got a walk-behind mower with a 4hp Briggs & Stratton engine. Bought it in 2002. I have a vague memory of having changed the oil once in its lifetime, but that’s about it. Still seems to run fine, plenty of power, not particularly burning oil (no blue smoke). Takes maybe half an hour to mow the yard, once per week from May through September, so it’s got maybe 150 hours of run time so far.
Back when I had a lawnmower, this is what I did, with an exception. Typically I didn’t buy specific oil for my mower, and used whatever remnants were lying around the garage (typically half-quarts of synthetic oil used in the cars). If I did buy oil, it was usually either straight 30HD or 15w-40, as strangely enough, those burned off the least, even compared to the synthetics.
But otherwise, one change a year in the spring before the mowing season got going. I’d also take the blade off and sharpen it with a file, and I’d also replace the little paper filter on the engine as well. (6.5 hp B&S Quantum)