Put in to bat at the MCA International Stadium in Gahunje on the outskirts of the city, Gugale (101) and his opening partner Chirag Khurana (71) laid a solid foundation with a 146-run stand.
The two batsmen, with their effective stroke play, made life difficult for Mumbai bowlers, who missed the experience of key pacers Dhawal Kulkarni and Tushar Deshpande, both out with injuries.
The 27-year-old Gugale hit 15 fours in his 191-ball knock, while Khurana notched 12 in his 106-ball stay at the wicket.
After Khurana fell, one down Jay Pande (68 not out) joined Gugale as the two shared a 52-run stand.
But soon after completing his fourth first class century, Pune-born Gugale was cleaned up by right-arm medium pacer Shubham Ranjane (2-30).
Skipper Rahul Tripathi (25 not out) was holding the fort with Pande at stumps.
Meanwhile at Vadodara, Baroda bowled out Chhattisgarh for a paltry 129 and then overhauled the total to be 36 ahead by close.
At Rajkot, Saurashtra skipper Jaydev Shah, who is playing his last match, led from the front, scoring a valiant 97 as the hosts managed to post 288 for 9 against Karnataka.
At Valsad, Piyush Chawla slammed an unbeaten century to take hosts Gujarat to 340 for 8 against Railways.
Gujarat skipper Priyank Panchal also proved his mettle by scoring a valuable 69.
At Pune: Maharashtra (Swapnil Gugale 101, Chirag Khurana 71; Shubham Ranjane 2-30) versus Mumbai.
At Rajkot: Saurashtra 288/9 (Jaydev Shah 97, A V Vasavada 38; J Suchith 5-104) versus Karnataka.
At Vadodara: Chhattisgarh 129 all out (Harpreet Singh Bhatia 37, Vishal Singh 26; Swapnil Singh 5-23) versus Baroda 165/7 (Yusuf Pathan 46 not out, Mitesh Patel 36; Vishal Kushwah 2-11).
At Valsad: Gujarat 340/8 (Piyush Chawla 109 not out, Priyank Panchal 69; Amit Mishra 4-78) versus Railways.