If someone woke up one Sunday morning with the intention to go to Mass, started the car and realized he had no gas, and had no way to get to church on short notice, he would not commit a sin. But not having gas in the car is not an all-purpose excuse for missing Mass. Someone who cannot afford to drive his own car has an obligation to find other ways to get to Mass, such as sharing rides with others at a parish or finding adequate public transportation. If that person is having trouble solving his problem of transportation to Mass, he should consult with his pastor for help. The pastor needs to know when some of his parishioners need transportation assistance for whatever reason, whether it be because they are too frail or too poor to drive themselves.