|Oil filler 'cap'|
The crankcase oil is Hallett's Sentinel Crankcase Oil SCC680. It is a viscous oil (ISO 680) and has the specific property of enabling water to separate from it and readily sink to the bottom where there is a drain valve to let it out. This water separation property is important with a Sentinel steam engine which inevitably encounters condensation in the crankcase. (Morris Lubricants also make an equivalent crankcase oil for Sentinels).
Expecting to use 10 gallons per engine, I decided I would log the amount added against the level indicated on the dipstick.
I filled the front engine first with these results:
1 gallon: Not on dipstick.
2 gallons: 1/4 on dipstick.
3 gallons: almost 1/2 on dipstick.
I added a couple of extra litres to make it 1/2 full. (I like to mix imperial and metric units!).
Then the rear engine:
1 gallon: 1/2 on dipstick!
Oddly, I didn't expect this as none had been added since emptying.
So why did the rear engine need 1 gallon and the front 3 gallons to be half full? Simply, I don't know! However, I have to conclude that there must be something that isn't oil also in the rear engine (which was the one without the sludge added!).
Perhaps inadvisedly, I'm not going to investigate this further for now but monitor it very carefully when initial testing begins.
As yet, I also don't know whether is it is best to fill to the top of the dipstick or not. At least there is some spare oil available!