Yes, driving too fast can be mortally sinful
Is it really mortally sinful to go really fast on the road?
Since it puts the driver and other people at mortal danger it is mortally sinful. Each of these acts cannot be judged generally because for a sin to be mortal it must:
- Be a grave matter
- be committed with full knowledge
- and freely chosen.
If you are referring to going a little above the speed limit, that could be sinful but it may not necessarily pose mortal threats to those around. But going really fast, especially in a crowded city could be a mortal sin.
Like we said in another place, the watch-word for anything we do is moderation. We must be temperate in the things we do, how we eat, drink, smoke and how we seek thrills. Those who are addicted to danger are risking their lives repeatedly for fun and this is sinful. Here’s what the Church says:
“The virtue of temperance disposes us to avoid every kind of excess: the abuse of food, alcohol, tobacco, or medicine. Those incur grave guilt who, by drunkenness or love of speed, endanger their own and others’ safety on the road, at sea, or in the air” (CCC 2290).