I recently acquired a 2009 Versa whose service history was essentially unknown. Mileage is currently about 69K. After a bit of sleuthing I've nailed down that it's had its 3750, 7500 and 15000 mile services as well as regular oil changes. Both the 30K and 60K mile services have not been done. Upon reading the maintenance guide booklet for the car I see that the essential piece of the 30K mile interval services is changing the coolant. Is it really necessary to have this done every 30K miles? I figure I will go ahead and get this done somewhat soon since it's apparently never been done (or, if it was done, was not done at a dealership, but given the history I've been able to obtain it's more likely it just was not done). Thanks for your insights.