This preventative measure wards off more than most motorists imagine. The engine, or the soul of the car, is what keeps it moving. If this engine isn't guarded, checked and given the care it needs to continue to run efficiently, the car becomes merely an outdoor couch you can park in your driveway. True, there are brakes, wheels and other necessary components that need our attention. Without the engine, however, having the rest of the car in working order isn't very beneficial.
So returning to Rabbi Luzzatto's discussion on cleanliness, he advises that there is much work that goes into maintaining cleanliness within ourselves - our souls are to what he is referring. But like the engine and the oil change, we don't perceive that our soul is getting gunked up with impurities; for all practical purposes, it seems like the soul is running just fine. So what, we don't check our "oil" to make sure it isn't running low. No matter that we haven't had a fresh intake of "oil" for some time. Just like the engine, we risk peril - greater peril in fact.
As Rabbi Luzzatto mentioned above, the sins which have obvious results are ones that we tend to be more careful about. Most of us don't want to appear sinful. But like the engine, if we don't maintain a high level of diligence in cleanliness - in thought, deed and those private moments of our lives - what is hidden and seemingly unthreatening becomes something which can overtake us. Those secret impurities and sinful tendencies lurk, waiting to wreak havoc on us.
Like the oil change sticker, we need reminders before us always that we need to be aware of that inner component that needs tending. By being meticulous in our life and making sure we have a constant supply of Torah, prayer and good deeds going on, we can ensure that our soul stays healthy and free from impurities.
Don't rationalize that everything going on inside of you is kosher. The yetzer harai (evil inclination) lurks within all of us. You are your first best defense against rationalization. Empower yourself by being vigilant, honest, diligent and be a true soul mechanic. Check your oil.
1.Chapter 10, The Virtue of Cleanliness, pages 54-55