first of all it isnt always so clear cut
for instance: there may be an early payment penalty, im assuming a 5 year payment term
at this stage the early payment fee may have already reduced to 0 or it may not have
(there is a perfectly valid reason for early payment penalties, however more so for an early mortgage repayment, but never the less)
consider what u might need the cash for in the mean time:
are there any more pressing matters (credit card debit should go first)
may be u want to hold onto some of the money for other possible emergencies where the money could save ur ass... say the possibility of losing ur job between now and whenever
if all ur insurance/health insurance is up to date and there are no penalties for paying the total off early and it is ur only debt besides ur mortgage left then yeah paying off the car is a good idea
(as the interest rate u r paying on the car will likely be higher than possible investment return)
perhaps consider paying R45k to the car, thereby reducing the monthly amount (or the term if u keep the payments the same amount) and putting the other half in a money market account - not the greatest return, but still its secure and u have access to it in case of an emergency
additionally - how did u come accross 90k suddenly
if u put this into ur pension account u can likely save some tax --> itll be taxed at a much later date, between now and then u earn interest on the portion that otherwise would have been taken immediately for tax
this difference is possibly enough to justify servicing the debt on the car at a technically higher rate