Mixing engine oils

[elad]

Hope this is the right forum
I have been running in my JD4110all summer Rotella 15-40
oil. Now with the colder weather coming, I want to put in a lighter oil. I now have Rotella 5-40 synthetic. Does anyone
know if it is ok to change to synthetic after running regular
oil. I haven't changed it yet because I'm not sure if I should.
I guess my question is, can I switch back and forth between the two oils without causing engine problems?
Any thoughts or advise is appreicated.

 

[RalphVa]

I've switched ALL my engines to synthetic now. The car engines had 130k, 188k and 60k miles when switched. No problems on any of them. The Gravely actually started using less oil after the 2nd change on synthetic. Seems to be the case with the 22 year old Benz, too. Only problem was on the Tacoma steering system when I put synthetic in it. A hose connected to a metal line without a clamp slipped off with the more slippery synthetic. Had to put a clamp on it.

Why don't you use 5w40 all year round? It'll still be 40 grade at higher temperatures and will be more viscous than at operating temperature whether you're using 5w or 15w. So, it's better on your engine to use 5w.

With dino oils, if you used something like a 5w40, you'd be using an oil with a lot of additives to get it to this VI (viscosity index, an inverse measure of how oil viscosity changes with temperature). With use, those additives would break down and cause either an increase in viscosity or a decrease. However, with synthetics, very few additives are used. They just change the manufacturing process to get the 5w vs. 15w levels at startup.

Ralph

 

[daTeacha]

Okay, what are synthetics made from if not dino bones? Nearly all our plastics are from petroleum.

I haven't made the jump to synthetics for the simple reason that the engine manufacturers require the same oil change interval no matter if you use $5 per quart synthetic or $2 natural. They should be reciprocally compatible with normal oils, however. No one can get every drop of either one out at an oil change, so they have to be.