Hi Dan,

 Thirty something years ago I was stranded in a cold snow storm in Watertown NY.  My cold 74 bus sat outside the motel for two cold days.  I had 20/50 oil in it.  I tried to start it after the cold and it hardly turned over.  I knew my oil level was a bit low so I took a quart of oil into the motel and sat it on the heater.  When good and hot I took it out and put it in the engine.  I waited about 20 seconds then tried starting the van.  It turned over a bit faster and started up! 

So, I’m no stranger to doing unusual things with oil. 

Still, I’d recommend simply taking out that thick oil and putting in a lighter weight for cold weather.  I think you should be careful to use the product designed for the purpose and the Mystery oil is not for replacing oil. 

I’m also a big believer in the mobile 1 synthetic oils.  And there are good options for cold weather and wide temp ranges.

I had 20 50 in the van when purchased.  On the way home at idle I had a oil light flicker happening.  It was very hot weather and long hot miles.  Still, after changing to Mobile 1 and 5 yeas no one has reported that flicker returning. 

So, I recommend  correct oil for the conditions and not taking chances.

Best,

Eric Caron 
85 GL Auto 

> On Dec 31, 2018, at 2:21 PM, Dan N <dn92610@GMAIL.COM> wrote:
> 
> Happy New Year to you all and your family...
> 
> I use 20W50 oil in my WBX engine... for the winter instead of switching to
> 10W40 I wonder if it's safe to remove half or a quart of oil and replace it
> with Marvel Mystery Oil (MMO) - my thinking is it will thin the 20W50 a bit
> for the winter...
> 
> thanks for your opinion...
> 
> dan