assuming 1:10 ratio for modern cars ( 1 liter : 10 km)
gasoline saved per day: 30,000*500/10=1,500,000 liters
gasoline saved per year: 1,500,000*365=547,500,000 liters
one liter of gasoline is approximately 0.873 kilogram, and one ton is 1000 kilograms
547,500,000*0.873/1000=477,970 tonnes
is he taking about a different type fuel?