What oil should I use in my lawn mower.

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This time I talk about multi-viscosity oil and how it differs from single weight oil. The mower sitting behind me has a big hole in the block that I blame on the viscosity modifying polymers breaking down and causing a loss in viscosity. I have switched my mowers to 30 weight oil exclusively to see if I loose any more engines.



18 thoughts on “What oil should I use in my lawn mower.

  1. I use 15W-40 diesel engine oil in my lawnmower with a side valve Briggs & Strattion 5HP motor for years and have never had a problem. The motor has got a lot of running hours up on it and it doesn't blow any smoke at all.

  2. I run a small engine repair shop and you are right on with this. I've found that the multi-viscosity oils just don't protect like they should. I'm also in Texas. I don't know anybody that mows in temps below 50 degrees. I've never even seen a snow blower in Texas. lol. A 5W-30 is OK for engines used in the winter like generators and log splitters but for 4 cycles in the spring and summer I recommend a straight SAE 30. 

  3. I always use straight 30 weight oil. I live in Florida. When you think of how hard those little engines work and how hot they get, it only makes since.

  4. Ben , put a bit of Marvel Mystery oil in the gas. Keeps the plugs clean and puts some lubrication on the fuel. Read up on MMO great stuff been using it for years.

  5. absolutely, 30w oil is highly recommended and is all we use in our mower shop. in fact, we are now being told that in the heat of the summer that 20w-50 would be great too

  6. I use sae 30w in my Ariens with 20% Lucas in a new engine wouldn't use the Lucas motors get wore they have more clearance thicker oil will not hurt one I had a Briggs 14 ran if for 6 years guy I gave the mower to it still runs

  7. I guess I have a different philosophy than most when it comes to what Motor Oil to use in a Lawn Mower. Mowers use so little oil compared to a car or truck, that it only makes sense, to put a high-quality, name-brand, common name and viscosity oil in my lawn mower. I have been using 10w40 Mobil1 Full-Synthetic in my Honda walk-behind mower for almost 17 years in the heat of south Florida. Never had a failure and never added a drop between changes (every other spring). Mowing St. Augustine grass near-weekly in south Florida heat should be testament enough. IMHO. . .

  8. I use 10w 40 my machine says 15w 40 but I use the 10w 40 standard car engine oil not synthetic not semi synthetic either

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