Lawn Mower Oil Maintenance


Check Your Lawn Mowers Oil

The following applies only to 4 stroke engines. For 2 stroke engines, special oil must be mixed in proper proportion with the gasoline.

The proper amount of oil is critical to the happiness of your engine. Too little and it may overheat, cause excessive wear, and in extreme cases (but not unusual), cause engine parts to seize and fail - very expensive. Make it a habit to check the oil regularly. Doing this after about every 5 hours of operation is generally recommended. More frequent checks - such as before each time you mow - are fine as well. A typical small engine in reasonably good condition does not use up a lot of oil but checking oil is easy and will not hurt.

Oil should be checked when the engine is cold or after waiting 10 minutes for it to drain back into the oil sump after running the engine.

Place the mower on a level area.

  • If there is a dipstick - remove it, wipe it with a rag, and then reinsert it as directed on the information sticker or on the stick itself - usually threaded fully back in place and then removed to read. Look at both sides of the dipstick to make sure it didn't just pick up oil from the filler tube AND reoeat the entire procedure be sure of the results. If the level is below or near the empty mark, slowly add the proper new oil to bring it up to just below the full mark.

  • If there is just a filler plug near the base of the engine, the correct level is just below the top - almost to overflowing. If lower than 1/4" or so below the lip, add new oil to top it off. (There may be exceptions to this but filling to near the top should be safe if you do not have your lawn mower engine manual handy.)

      If the oil level is high - you just bought the lawn mower or were careless in filling it last time - drain enough oil to bring the level back down to the full mark. Too much oil can result in problems as well - oil spraying out of various orifices or getting into other places where it should not be like the combustion chamber.

      If you find the oil level over the full mark or higher than it was before, gas may be leaking into the oil due to a flooded carburetor - a stuck inlet needle or bad float. If this is the case, the oil will need to be changed once the underlying cause of the leakage is determined. (This is only likely with float type carburetors such as those used on the Tecumseh engines used in a variety of Sears/Craftsman models equipment.

      If the oil is very low and you have been performing regular maintenance, there may be a leak or your engine may need a ring job. Excessive oil under the deck - on the shaft or blade adapter - would indicate a bad bearing or oil seal. Noticeable blue smoke while running would indicate that excessive oil is getting by the rings into the combustion chamber.

      Typical oil capacity is just over 1/2 quart (usually about 1-1/4 pints).

      About engine oil

      For the common 4 stroke engines such as Briggs & Stratton or Tecumseh, you don't need to buy specially high priced engine oil. The type likely used in your automobile will work fine and will be much less expensive. Although small engine manufacturers may recommend SAE 30 oil, they usually also state that 10W-30 or 10W-40 are acceptable substitutes - and these are what your car probably uses. New oil should have at least the SG rating though if you have some SF in your garage, that will be fine also (for your lawn mower, not your car!). However, there are situations like equipment that must run in extremely cold weather (probably not a problem with grass mowing!) where specific alternative oil recommendations should be followed.

      The capacity of a typical small engine is just over a 1/2 quart. This will probably cost you about 50 cents - a very worthwhile investment!

      However, some people do swear by synthetic oil. I remember it worked pretty well on my bicycle as well :-):

      (From: Daniel Pope ([email protected]).)

      Synthetic Motor Oil in the crankcase and Marvel oil in the gas is the only way to go!

      I have a $1,900 MTD tractor style mower with B&S engine (L head twin). It has over 800 hours and 9 years on it and I mean rough hours (bahaya grass and hot weather). The engine does not use a drop of oil (changed every 30 hours) and the compression is the same as when new. These other guys can have there $5,000 fancy mowers. I'll use that money to buy a truck.