I need a lighter oil for winter in my Yanmar 3 cyl diesel as I don't or can't have it plugged in and the 15W40 is too heavy to allow the unplugged engine to start. Thinking of using a 5W or0w oil. Will this work better?
Welcome from Ea WA state. Kubota recommends either 15W40 or 10W30 for year round use. I would post on the fuel/oil forum as mguitas suggests. Personally, I use 15W40 year round and have no difficulties. However, you probably get a little colder & for longer periods.
10w-30 semi-synthetic or 5w-40 synthetic Rotella work fine for me. 5w-40 synthetic Delo is also good and easily available here. It's what will go in my machine in another month.
I just bought oil for my B2650 and dealer said to use 10w 30 for winter use . I use 15w 40 rotella with my M5700 all year long but that has a block heater .
I use NH Mastergold 10W-30, but I plug it in. I wouldn't dream of starting it at -5F with that oil unless it was plugged in. I would use 5w-30 for colder starts unplugged. I used 15W-30 last year and plugged in. It was more sluggish than with 10W-30 in starting. In Maine 10W-30 is an all season oil for my tractor (rarely in the 90's).
For those of us whose climate is "far north", the 5w-40 and 10w-30 give us an oil that is suitable for year around use. These oils "fit" us and our climate well. I've never used the common 15w-40 and likely never will.
Nonetheless, I do indeed like my plug in block heater. When it is −30, it gives me confidence to fire up that diesel and put it to work.