OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions on Other Engines Dodgy dipstick on Kohler engine - how to check oil accurately?

I have a SupaSwift mower with a Kohler engine. Ever since buying this mower I have had a problem determining the correct oil level. This may sound strange, but let me elaborate.

I go out in the morning and check the oil level after the mower has been sitting in the shed overnight or for a few days/weeks, and it always shows oil way up on the dipstick. And I mean WAY, WAY up! If the measurement were accurate, the oil level would be about 10X above what is recommended. This is ridiculous, as I never added that much oil.

So I wipe it off, pop the stick back in, wait a few minutes and check it again. This time the oil is showing at the right level, just below maximum but above the "ADD" line. Spot on!

I wipe it off and check it a third time, wait a minute or two or three, and check it again. This time it is showing below the ADD mark. How can this be?

I get really frustrated with these phantom readings and cannot really understand why it does this. I never have this problem with any of my B&S engines. They always show exactly what is there. I am sure I have not over-filled the sump as I only put in the amount recommended when I last changed the oil. But this "dodgy dipping" does not make things easy! I am never 100% sure if I have the right oil level, too much, or not enough.

Has anyone else ever had this problem with Kohler engines? The dipstick is quite solid metal construction, so there is no way it could be bending when it is inserted. It goes down smoothly and fastens in place with a few screws of the handle. I have even tried wiping off the dipstick after use, as I wondered if maybe the oil is sticking on the upper parts of the dipstick after the mower has been turned off. But I still get the same result. It shows way too much oil, but then I wipe the stick off and pop it back in for a few minutes and then it shows a more accurate level. Then I take the measurement again and it often deviates wildly up or down from the last measurement. This drives me nuts. I cannot understand why it does this. Can anyone suggest a reason why?

I think I may have found the answer myself on another forum. Seems you can get a kind of "capillary creep" happening on some dipsticks over time. The oil is attracted to the smooth finish on the stick and rises up it. There can be various pressures involved in engines too after you turn them off that can cause the oil to push up slightly into the dipstick tube.

I guess this is why they always say to dip, then wipe, then dip again!

So that answers one of my questions, but not the reason for the varying readings on third and fourth dip etc.

I have seen this on Kohler engines and other engines too. Just let the engine breathe a minute or two with the dipstick out and the oil level should read correctly. It is cause by crankcase pressure and vacuum due to temperature differences and how well the manufacture are sealing the systems today to meet EPA guidelines (rules). BTW Kohler uses a reed valve in their crankcase venting system which is also playing a role in this which close unless crankcase pressure is high enough open the reed which could be slightly stuck closed by oil. Oil like any liquid will take the path of least resistance.

Thank you for the explanation. Yes that all makes sense and I will follow your suggestions.

If you know what model Kohler you have, the manual will point you in the right direction for correct oil capacity and then you can check against your dipstick.

If it's a K90 or K91 (4hp) you will need about 500ml.

Thanks Geoff,

Have had no further problems with this since following AVB's advice. I guess I am too use to old machines that you either filled to the point of overflow or checked with a dipstick once and a while and got a fairly accurate reading. I was a bit puzzled when I got this mower and suddenly found lots of bizarre readings. First time it happened I was sure I must have overfilled the sump. :-)

Cheers

The oil gets churned up by the pumping action of the piston - early engines relied on this for lubrication! Google - "splash lubrication". I suspect this is why the dipstick appears coated with oil