Read few articles on the net that it is safe to mix oil weights as long as both are of same category. So as not to waste
my in-stock TOP 1 5w/50 FS, I would like to mix it with a ZIC A+ 5w/30 FS with the following ratio:

1. For a 4L-oil capacity gas engine:

Top 1 : 2L
ZIC A+ : 2L

will result to Brand X 5w/40

2. For a 6L-oil capacity gas engine

Top 1 : 3L
Zic A+ : 3L

will also result to Brand X 5w/40

You thoughts please .......... thanks.