Our motorhome is old, a 1992 American Eagle we thought about changing to synthetic but changed our minds. The manual says change oil every 5000 miles so my husband stuck with the 15 40 rotella. Since we are changing it frequently enough we don't think it will make a difference.
We keep it in a garage here in Indiana. Last winter when I was going to leave on a trip and it was in the 20's and 30's I put a heater near the engine for a day and the night before I left. The engine kicked off ok. I have an engine heater to plug in but have never used it. I assume it works, may try it this winter before we leave to see if it works. On the generator we have a heater switch to hold for 30 seconds and it starts right up. So the oil we are using is fine.
Also as old as it is we did not change to synthetic for the transmission either, if it were newer we would have.
