I haven't seen Zic 4t in 20W-40. As it comes in the follwing sepcifications:
[TABLE]
<tbody>[TR="bgcolor: #d9e2ee"]
[TD="class: txt03, width: 20%"]10W/40[/TD]
[TD="class: txt03, width: 20%"]10W/50[/TD]
[TD="class: txt03, width: 20%"]20W/50[/TD]
[/TR]
</tbody>[/TABLE]