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Unexplainable oil levelon dipstick.

L

Lesformore

Member
I have a Toro walk behind lawn mower with a 6-1/2 HP motor. Before I use it I check the oil. I don't move the mower or do anything but pull the dipstick. It shows oil about 3 inches up the stick. I wipe it clean, check again and the oil level then is half way between the add oil and full mark. It's done this since new. It's a Tecumseh vertical shaft engine. It runs fine and is about 8 years old. How does this happen ?
 
It happens because of a combination of splash lubrication and surface tension.

While the engine is running the dipper finger is throwing oil around all over the inside of that engine. The dipstick actually touches the plastic housing in many cases including yours. Oil that gets thrown up by the dipper finger sticks to the dipstick and the tube due to surface tension. When you pull it out and wipe it down, the oil goes back down the tube and any remaining oil just smears along the tube.
 
My 20 HP Kohler in my Gravely front deck mower shows the same way. While running, the oil is hot and is forced from the dipstick tube and when it cools, it is drawn up in the tube.O-ring on the dipstick has a good seal and won't allow the oil to return to the oilpan. I always remove the dipstick while I am adding gas and let it settle.

Gene
 
(quoted from post at 21:38:14 05/24/12) My 20 HP Kohler in my Gravely front deck mower shows the same way. While running, the oil is hot and is forced from the dipstick tube and when it cools, it is drawn up in the tube.O-ring on the dipstick has a good seal and won't allow the oil to return to the oilpan. I always remove the dipstick while I am adding gas and let it settle.

Gene
Click to expand...
On the nose Gene.
Good explaination.
 
"While running, the oil is hot and is forced from the dipstick tube and when "it" cools, it is drawn up in the tube.O-ring on the dipstick has a good seal and won't allow the oil to return to the oilpan"

"It" would be the crankcase gases in this case. When the hot air/gases in the tube cool they create a vaccum that draws oil up the tube. Break the seal and it drains back into the case.
 
40 years ago i learned the hardway on a borrowed dump truck ,, owner told me to watch the oil because it uses some ,,just was doin low rane hauling off road ,with no grades .i was used to pullin the stick and trustin 1st readin ,,.ended up losin oil pump
 
The Onan on my JD318 does the same thing. Even after sitting for a week, the oil is up several inches on the dipstick. Wipe it clean and check and it's in the correct range.
 
I had a mini bike engine as a kid that I could never get a reliable reading off the dipstick. There was simply no way to cleanly pull it out of the crankcase. 9 times out of 10 there was oil all the way up the dipstick even if you pulled it and wiped it several times.
 
My 16 hp Briggs single cyl. does exactly the same thing, doesn't matter if it sits all winter still shows way up the dipstick first time I pull it out. Wipe it off, recheck it, and it is accurate.
 
I have a craftsman with 20.5Hp Briggs 2Cyl.. and ti does the Exact same thing... I always wanted to know why?? just a vaccum on the tube.. larry KF4LKU
 
As said before, the oil will stick to the dipstick for MONTHS when left undisturbed.

Especially if the dipstick has letters engraved into it, or hatching, or holes. Those give the sticky oil something to cling to.
 
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