OTOH if low mileage is due to many short trips and not much highway driving, it would be considered severe service and should be on the lower mileage/time schedule. Cars that never get fully warmed up, sit around alot, etc can still have contaminant build up, moisture, etc in the oil, which may be more detrimental than lots of highway miles. I go by the 6 months service always if I don't get the miles. It isn't expensive and it's good "insurance". You don't have to pay Lexus prices just for oil and filter changes. I think it's especially important if this is your first service since breaking in your motor.