OK
Thanks one and all.
i must say, in spite of a variety of opinions, I don't think any are bad.
I'd be fine if I did all or none.
I do feel much better about the "acid" issue and will simply not do anything this December.
I will change the oil once in the water in March. Normally, I would change the oil at the end of the cruise season as i see no point in leaving dirty oil in there if i am going to change it in the spring.
But next year i am not planning on having a long winter lay up.
I started using 15w-40 in Maine since it was the only large quantity oil available at Walmart. If it's good enough for the fishers, it's good enough for me.
Northern Europe is pretty much the same, maybe colder in the summer.
15w oil and 30wt oil pretty much flow the same at 50°.
The real issue about multi weight oil is that most wear happens at engine start, so the initial "cold" viscosity is far more important than the "hot" viscosity.
In 1969 the oil recommendations for my little BMW 1600 are
exactly the same as for the Ford Lehman. I even think they used the same horizontal temperature bar graph.
And while the problems with viscosity extenders 40 years ago were an issue, there is not one high performance engine that calls for single weight oils nowadays.
But having said that, i simply do not think it matters. Just as i spend an extra dollar to buy the oil from Ireland and not Poland, but I do that as a matter of diplomacy and nothing else.
I think I will just defrost the fridge and be done.
Thanks All and yes Capt Bill, I have already requested the oil test kit from Blackstone. Thanks.