The opposite is also possible: those bought with loans are probably bought new, and would be expected to be held onto for longer. Older cars are cheaper and are probably bought more with cash. They probably also kick the bucket / are re-sold more quickly.
Not all cars are bought with loans though.
Then those data points will have 0 for their loan years and it should bring dowm your average years.
Are those data points even included in the set?
The opposite is also possible: those bought with loans are probably bought new, and would be expected to be held onto for longer. Older cars are cheaper and are probably bought more with cash. They probably also kick the bucket / are re-sold more quickly.