1995 T-Bird 4.6 V8 - Correct Oil
 

My Tbird calls for 5W20 oil. i told my mechanic that I noticed the car using oil, even though it does not appear to be burning it. My mechanic told me that I could use 10w30 during the hot months of STL Missouri.
I am a bit scared to try a different oil. Does anyone have an opinion on this?
Will the car use less 10w30 compared to the 5w20 ?
BTW..........I am full synthetic at this time

How much is used over how many miles?
It should be fine as a summer oil, or, use 5/30..
Me, I'd stay with the OE recommendation on a low/er mile engine, maybe an increase on a higher mileage engine, but I wouldn't suspect you'd see a significant decrease in consumption.
Not only does viscosity slightly affect MPG/emissions, but is more for tighter engine build tolerances, more so when cold/start up..