Hi guys,I recently purchased a 2001 hd with an 8.1 and was wondering what you guys run for oil in the winter and summer.Thanks for any info

Assuming you are in the north somewhere since you are concerned with winter:)
Synthetics do offer an advantage in cold weather. Lower point points and cold crank viscosity. As for weight, looks like 5W-30 is recommended and is fine. If you are in extreme north, there are 0W-30 that would offer a little more. Also better heat transfer in the summer. I use it in my wife's car year round.
Heath

5w30 syn should be ok

5/30 Year 'round

I run this oil all yr in my 8.1 ,it uses no oil when running 10w30 Shaeffers.http://www.schaefferoil.com/datapdf/703.pdf

I run 10W30 Mobil 1 syn year round. Has an amazing flow rate at very cold temps. Very high boiling point. I don't like thin oils in these big blocks. They tend to use a lot more of it, and the oil pressure is low.

I have used 0-40 full synthetic year round for years. Works just great in winter. Hurts a-bit when buying it, but well worth it.:)

Thanks for the info guys.