Oil/tranny fluid change

I know all about the OLD wisdom which was about draining an engine with the oil hot back when everyone used single weight fluids.
Personally I look at it another way and that is by draining the oil before running the engine, the oil has already drained down to the lowest point as well as any contaminants. Since I am draining at the lowest point, I figure I get more of the oil and contaminants out by draining it after the engine has sat for some time.
The same goes for the transmission.
Besides the obvious that it is easier to work on a cold engine, I can see no advantage to warming the engine and transmission up before draining the old fluid. I've been doing it this way for years on my motorcycles, airplanes, trucks, RV's, racing and street vehicles.

Yes on the engine and no on the transmission.

K Charles wrote:
Yes on the engine and no on the transmission.

Why not trans?

Actually, were it mine, "neither".

While you can get a diesel engine's COOLANT up to operating temperature at high idle, you will not get the OIL warm.

Better to wait until you can drive at least 25 highway miles and change both.

I just returned fro Fla on Sun it took 3 days to get the tow car out due to the ice and snow. Hope to go back next week with the MH with car it tow maybe today's rain will melt the snow off the roof. Another guy I know in Milford said it took his DP an 1 hr to come up to temp when the out sides temps in the 20's. Can you get underneath with all the ice to change the oil?

You wont get either warm enough.
I know it's not preferable but in a case like that it would be better to just change it cold.

Another way to look at. Let's assume you take it in for the oil change and drop it off the night before. Would that shop send it out for a 25 mile trip and then do the work on it?

Four feet of snow?
Where are the pictures!
I haven't seen snow in ten years!

wolfe10 wrote:

Better to wait until you can drive at least 25 highway miles and change both.

That can't happen,once I take it out of its parking spot it's not going to be able to go back until after our trip. I have no other place to store it once I get it out. It's either go the trip the way it is or change it cold. I haven't had the motorhome very long and have no maintaince records. It has 65k on it right now. I did find a receipt for a oil change that was a year old and now has 5k miles on that oil. What is the down side of changing either cold? I'm guessing it can't be any worse than leaving it the way it is?

The fluids in your engine and tranny are multi-grade in the engine and synthetic in the transmission. They will drain just fine in cold weather and all of the old fluid and contaminants have already drained down to the sump.