5W30 dino is recommend for my 98 Expedition (110,000 miles), I live in a moderate climate, if I change to a full syn. oil which flows easier dino should I use 10W30 syn.

 

No.

Use what is recommened. Switch to synthetic if you want but keep the weight the same.

 

While your owner's manual recommends 5w30, what does it allow besides that? Some will allow for 10w30 above 0F. Not too long ago 10w30 was recommended with 5w30 allowed for under 60F. But with synthetic it may not matter. A good 5w30 synthetic likely has no viscosity index improvers and so would be about as robust as a 10w30.