What is the maximum outside temperature at which I can run 5W30 Mobil1 
Synthetic in my van's engine?  

It will be warming above freezing regularly soon, but it is around 0 
degrees F in the morning.  My mechanic says I could run it year round, 
and my FLAPS man says it may already be too warm; he runs Mobil1 10W30 
year round.  

Thanks for any help.  I have a case of the 5W30 and want to use it, but I 
suppose I could store it until next fall.  

Chris Wyatt
'87 Syncro GL
Fairbanks, Alaska