to calculate the amount of petrol sold for automobiles in mumbai in a month (30 days), we need to combine various pieces of information provided: 

1) autos and buses in mumbai run on cng, so they do not consume petrol. 

2) petrol consumption in mumbai is triple of that of kolkata and half of that of delhi. 

3) diesel consumption is 65% of the total fuel consumption at oil retail stations in mumbai. 

4) petrol consumption in major metro cities in india has grown 3 to 4 times during the last decade. 

5) the typical fuel efficiency of cars is around 15 km per liter and that of a two-wheeler is 60 km per liter. 

6) some automakers claim a fuel efficiency of 28 km per liter in india. 

7) daily petrol consumption for a year in kolkata was around 1.5 million liters 10 years back. 

8) 5% of car owners' households in mumbai own two cars. 

9) oil retail stations in mumbai sell cng, petrol, and diesel only. 

10) on average, a car in mumbai drives 500 km every month, and a two-wheeler drives 300 km every month. 

11) cng consumption in mumbai per day is 29.5 million liters. 

12) there are 30 million households in mumbai. 

13) 30% of households own at least one car, and 60% own a two-wheeler in mumbai. 

14) cars and two-wheelers are the main automotive consumers of petrol in mumbai. 

15) mumbai residents and businesses typically consume 90 million liters of petrol and diesel together daily. 

16) travelers entering mumbai by road in their own cars consume around 0.5 million liters of petrol every day.