Can someone tell me the difference between the Volvo Penta DP versions from the mid to late 2000's.

DP, DP-A, DP-S, DPS-A

I see a lot of different DP versions, what's the difference?

https://www.fybmarine.shop/volvo-penta-sterndrive-oil-capacity-chart

There is no short answer but above website has a download for the Volvo Penta ID chart; which is good place to start.
Hope that helps some....JB @InshoreOff

Thanks for the link. I did get some good info from the site and now have a better understanding on different models.