I get this on the end of the dipstick in cold weather at preflight. O200, Shell 15W50, oil and Tempest filter changed one month/6 hours ago. Never run for less than 1 tach hour invthe air. Oil temp doesn’t rise much above 80,°C.
It’s water in the oil. Your oil temp is a little low, the ideal range is 180-200 F, or 82C minimum (ideally).
The baffling or cowling for an O-200 typically has some features that direct air onto the crankcase and oil tank, and not onto the cylinders. Blocking those might raise the oil temp a little without raising CHT. There is also a sump blanket used by some. These engines don’t typically have a thermostatically controlled oil cooler.
You might consider an engine dryer to get rid of the water and to keep the inside of the engine dry when hangared. A few drops of oil in the bottom of the sump will not be a huge issue – but moisture in the rest of the engine – particularly around the camshaft – will reduce engine life. I use the “black max” engine dryer – they have a 220v version.
Something I also do is to remove the oil filler cap just after landing to let the “steam” out. Only takes a few minutes.
Check back with me in 20 years to see if this helped.
Rotax recommends to make sure that you reach a min of 100 C at each flight to boil-off any water in the oil. When it’s ‘cold’ here I do that by extending flaps and do a high power, low speed climb of 1.000-2.000 ft. Would that not work in your aircraft?
Taking the oil cap off after every flight is a very good idea, as long as you remember to reinstall it. The cap on a Continental is large and readily allows water vapor to escape. The caps also rust on the bottom, there’s plenty of hot vapor in that area.
O-200 engine installations are often over-cooled to allow for hot weather operation, like many air-cooled engines and especially those that don’t include a thermostatically controlled oil cooler. You can’t typically make one run at e.g. 100 C oil temp in cold weather without limiting oil cooling somehow.
Thanks guys. I’m grounded until 26/12, can’t drive to aircraft until 13/12, due to cataract operation 5/12. (Coinciding with annual P to F inspection.)
I’ll try the climb, but I don’t think it makes a difference. I’ll try leaving the cap off.
I’ll look at ways of raising temp.
A hangar neighbour who also has an O200 on Shell 15W50 adds Camguard and thinks this protects him. His flights are shorter than mine, and slightly less frequent
Just guessing here, in case it helps…. Allowing for the fact that the dipstick may not be at the exact bottom of the sump, there’s no real measure of how much moisture you’re dealing with.
For the cost of an Aero engine, vs Oil, personally I’d dump that oil and replace it rather than trying to boil off the water content. Then take whatever steps to reduce it’s cause.
If you rest the old oil in a sutable container you may be able to see the water separate out and skim off a load which can be used a top-up for the future.
Water in oil has caused Corrosion in oil filters in the past, so I’d be replacing that too.
I used to get this kind of sludge when using the old Exxon Elite oil.
Tons of it under the rocker covers too.
