If the outside temp is primarily above 60 degrees farenheit, I use 10-30
If the outside temp is primarily BELOW 60 degrees farenheit, I use 5-30
Topping off a crankcase full of 10-30 is absolutely not an issue. As a percentage of the total oil, topping off is insignificant and changes nothing. Unless you are two quarts low!
Without data, all you have is an OPINION!
Past Jeeps: '49 ******, '81 Scrambler, '88 Comanche
Current Jeep: 1999 XJ Sport, bone stock, daily driver.
I work on Jeeps!!