How To Easily Change Your Lawn Mower Oil

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Subject: Snapper SPV21

When you own a lawn mower, it’s important to remember the basic maintenance that should be performed on your unit at regular intervals. To keep the engine running in top shape, you need to change your lawn mower oil fairly often. It’s not a difficult process and only takes a few minutes to complete.

For our demonstration, we will be using a Snapper SPV21 mower; it is recommended to change this machine’s oil after every 25-50 hours of use. Consult your manual for recommended time frames for your mower.

If you have recently bought a lawn mower, the oil needs to be changed after the first 5-8 hours of use. This is to get rid of any metal shavings or debris that might have been left in your machine during manufacturing and assembly.

Supplies Needed:

  • High Quality SAE 30 weight motor oil (consult manual for what type you need)
  • Container to collect old oil (milk carton or can)
  • Paper towel to wipe dipstick

Remove spark plug wire

1. The first thing you need to do is drain the fuel tank. You can either let the gas run out while you are mowing or siphon it out.


2. Disconnect the spark plug wire and keep it away from the spark plug. This is for safety purposes.

3. Pull out the dipstick and tip the mower on its side to drain the oil into a container. The simplest and cleanest oil change is by tilting your mower on its side to drain the oil from the top. If your mower comes equipped with side or bottom plugs, you can drain from there as well. Allow ample time for the oil to drain.

Tilt your mower

4. After the oil is drained, place the engine level again. For our unit we need to add about 18 oz. (or 0.5 liters) of new oil. Fill the tank to the FULL line on the dipstick. Avoid overfilling your oil tank. If you accidentally put in too much oil, turn the mower on its side again and drain a little, then recheck the level on your dipstick. Repeat until you have the desired level.

Things to Remember:

Never tip your machine with the carburetor or spark plug down. The oil will saturate the air filter and cause hard starts or cause the mower not to start at all. If you do accidentally contaminate the air filter, it will need to be replaced. Drain the oil through the dipstick tube into a container. Allow sufficient time for all oil to drain. Dispose of the drained oil properly.

What is the purpose of oil and how does it work?

Oil serves two purposes: it lubricates the engine and it works as a coolant for the engine. It lubricates by separating the moving metal components of the engine. As the oil deteriorates it loses it ability to perform this function and can cause damage to the engine if it ever gets to metal on metal. Lawn mower oil acts as a coolant by transferring the internal engine heat to the cylinder block and then to the outside air. It is important to prevent damage to the engine because blow by can occur in which oil is shot into the combustion chamber which can cause increased hydrocarbon emissions.

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What type of oil should you use?

Make sure to use a high quality detergent oil that is classified as for service SF, SD, SE, SC or better. Other factors depend on the temperature you will be operating in. If you normally operate above 40 degrees then you should use a 30W. 10W-30 is acceptable but most engines use it more rapidly so keep a close eye. Do not use 10W-40 because it can cause most engines to fail rather quickly. Make sure to check your mowers operating manual to see if they recommend a special grade of oil, but most likely you will be okay with what we recommend.

Author Bio

Matt Morrison is a lawn expert, homeowner, and website hobbyist from Texas. He enjoys working on his own lawn and helping others make their lawn the best it can be. You can read more of his articles here.

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  1. Ares Totembopper

    I hate Brigg’s vertical shaft engines – I tilted the thing to drain the oil and all of the factory oil in the air filter sponge leaked out all over the place.

    Why can’t these assholes come up with a better solution – horizontal shaft engines on snowblowers and automobiles are so much easier to deal with. NO MORE TILTING, FLOODED CARBS, OIL MESSES, KNEES ON THE GROUND, CRAPPY OIL DRAIN OPTIONS – I HATE THOSE ENGINEERS AT BRIGG’S YOU ASSHOLES!!! AND FER CHRIST SAKES, PUT A DAMN DRAIN NUT ON THE FUEL TANK SO I CAN DRAIN THE THING EASILY, LIKE C’MON YOU BUTTHEADS.

    • Some designs are certainly more unfortunate than others. Sorry to hear about your misfortune Ares.

    • And the Darwin award goes to…

      There’s a specific side you tip a mower on, be it Briggs or Tecumseh, and it’s the side opposite the carburetor. Otherwise oil leaks into the carburetor, fuel and air system. It specifically states this in the manual. It’s also common sense.

      I think you should just use a reel mower from now on, or have someone do it for you since you are clearly unable to complete simple, basic maintenance, then throw a fit at your own stupidity.

  2. Excellent. That is a succinct article and tells me everything I need to know. 1. Remove spark plug and tape the mechanism for safety. 2. Drain the gas. 3. Remove the oil dipstick and tip the mower, but be sure to keep the carb and spark plug “high” so tilt the other way. 4. Get bonus points from wife for being manly. Thanks Matthew !

  3. My lawn mower is blowing white smoke working for a minute then stopping..have I overfilled oil?..when you say carb down ..that means avoid carberator being down when you are titlting?

    • Mike,

      Could be or you’re leaking a little oil into the combustion chamber from somewhere. I’d recommend taking in the mower to a repair professional if you feel like it’s a problem. Yes, avoid carb down while you are tilting.

  4. My push lawnmower is running but poorly and is guzzling gas in the process. We just finished the yard and what normally takes 1 tank of gas to do, took us 2 full tanks this time. The engine revs fluctuate from a medium to a low (so low that you think it might stall out). This is particularly odd since this a Sears push mower with no controls for the revolutions…you just start it and mow.

    Any ideas what could be going on and what I could do to remedy it?

    Thanks for your advice in advance!


    • Tom,

      It sounds like you might be having a carburetor issue. I don’t know how mechanical you are, but you could take yours apart, clean it thoroughly, and check for any leaks. One simpler method to try is mixing in some B-12 Chemtool with your gas. Make sure you follow the instructions on the label. I think its approximately 1 oz. per gallon. Keep in mind that the whole bottle is for putting in a full tank of gas in your car. Good luck!

    • could also be a dirty/blocked or oiled up air filter. Eventually it wont even start if this is the case. maybe

    • I know that this is late, but did you make sure that you don’t have the choke on? My mower has the choke switch hidden around the carburetor and will eat gas like a pig, plus idle low enough that it seems it might stall.

  5. Narendra Reddy

    While moving suddenly stopped working.

    Self propelled lawn mower doesn’t start. ratchet doesn’t retract.

    Checked the engine oil, it is completely dried.

    Can you please tell me what the issue could and how to fix it.


    • Reddy,

      It sounds like this mower’s maintenance was few and far between. I’d personally take it to a local lawn mower repair shop. Also, keep in mind that sometimes it’s just time to buy a new mower. Make sure the next one receives regular maintenance such as oil and filter changes. Good luck!

  6. I was given a newer probably 3-4 year old Dynamark mower with 3.5 hp Briggs engine. I could not find a drain plug under the mower, so I tilted to drain oil. Then it didn’t want to start. The sparkplug was coated with oil. Was this caused by tipping? After several cleanings I got it going..

    • Joe,

      Probably so. Never tip the mower with the spark plug or carburetor down. Better luck next time!

  7. I have a Snapper mower model 84425 is a need to change the oil but the oil gauge is not original so I do not know how much new oil (in ml) should I pour. You can help me.

  8. Dejan,

    For future reference, you can lookup your mower’s manual on the Snapper website here:

    I’m not sure what you mean by new oil gauge, but your dipstick (even if it’s new) should have the proper fill line. I’d try out 0.5 liters (or 500 ml in your case) of oil added to an empty tank first. Then check your dipstick as recommended in the article above. You can add or remove oil as needed, but you want that line to meet up with the full line. Good luck!

    • Measuring rod for oil is handmade and is not marked with lines for the maximum required. When I replace the oil, I will mark this line on the meter. Now I know that the technical specifications ranging from 0.5 to 0.6 l of oil. I got the mower as a gift so now I have some problems but they are resolved.

      Thank you very much for your time

      • Dejan,

        Now I understand. I think your decision is about the best you can do with the hand you were dealt. You’re very welcome. Let me know if you have any more questions and I’ll do my best to help.

        • Do you know what should be the length of the meter the oil as it is handmade and I can not find the original in order to determine whether it is well made.Now I know how much oil is needed, but later when I checked I will not know if the oil level is appropriate prescribed.

  9. Unfortunately, that is beyond the scope of my knowledge. One possible suggestion is to purchase a new oil cap and dipstick. Check the manual to make sure you’re buying the right part. I will say that it’s probably very difficult to find one. Good luck!

  10. Blue Hair Don't Care

    I have no oil

  11. can you use pensoil to fill up the tank

    • Oil made specifically for lawn mowers is usually recommended, but any oil is better than no oil 😉

  12. Marissa Groeneweg

    Most vehicle manufacturers recommend changing the oil once a year or every 7,500 miles in passenger car and light truck gasoline engines. For diesel engines and turbocharged gasoline engines, the usual recommendation is every 3,000 miles or six months.

  13. Mike,

    After reading all the above, I must say you are a man of patience 🙂 You deal with all this very well, and keep your composure. People like you are needed to be able to keep your cool working with all different types of people. Thank you for
    your time and knowledge!

  14. I have a morrison lawn mower and its does not want to start. i checked the oil and its totally black. I checked for spark and it has spark. I drain out the fuel and put new fuel in but it still does not start. need help on this. Thanks.

  15. Are there any oil brands that make a designated motor oil?
    Seems like, since lawnmowers run hotter and higher RPMs than a car it would need a better oil.
    They only require 18-24 oz to fill so a more expensive synthetic would only cost a few $ more.

  16. Dingdong Rung

    I mowed about 20 times since acquiring my new TroyBilt walk-behind (about 30 hours of use). It became difficult to start, so I changed my air filter which helped for the next mowing. After that, the poor engine gave me the same symptoms as Tom of June 2011 – difficult to start, and alternately revving / slowing. Seeing your post here, I realized my mistake and changed the oil. It starts now, but it’s weak, like I’ve killed a couple of my 6.5 horses and they are a drag on the rest of the team. I will clean the carburetor next, but I’m afraid I’m scoring my engine with metal shavings and doing irreparable harm… Short of rebuilding the engine, is there anything I can do?

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