Oil Change: Please Advice

[kingbah]

It's time for an oil change for my 84 300SD with 148k miles. Currently on Rotella 15w30 and I am wondering what weight of oil I can use for summer, winter or year round (if possible). I live in the Washington DC area. Right now I am getting about 27 city and 35+ hwy. I am really impressed with this car and I look forward to maintaining it. I knew very little about diesel cars before joinging this site but now I am learning every day. Thanks.

[RogerJones]

What does it say in the handbook? Can't see the need for anything but a year-round multigrade in DC. Why not stay with the Rotella? The range looks a bit narrow, but I doubt that it matters in that climate (we'd probably go 10W40 in the UK). I'm no expert, but, as ever, I reckon frequent changes are more important than choice of oil, within sensible limits.

[Rmac58]

I use Rotella 15W40.
Some folks swear by AmsOil.

[NKJohn]

I would consider 15W 30 to be too thin for your diesel. 15W 40 would be a good year round choice

[kingbah]

Thanks all for your help.