Is it ensure, insure, or assure?
"to reach the maximum level," by 1986, colloquial, from maximize or related words. Related: Maxed; maxing.
At the most; at the highest limit: I do three cars a week, max (1970s+)
To win; do the very best (1950s+ College students)
to the max
[fr maximum ''the highest possible grade,'' found by 1851]