Can I top up with petroleum motor oils when the last oil change was done with synthetic motor oils?

The vehicle is a Mitzubishi Express van and the last oil change was done 4 months ago. I have a small leak and it needs a top up, but I don't want to purchase more synthetic oil until i get the leak repaired, due to the cost factor.|||Top it off with regular would dilute the existing synthetic. Nothing will go wrong, but if it's not too low, you may just go without topping off.|||YOU CAN TOP OFF,BUT I WOULDNT ADD MORE THAN A QT.|||won't hurt thing but I do recommend that you use "Lucas Oil" products, it will save the life of your motor and will improve your gas mileage|||It will not make a difference. I would not spend the extra money on synthetic oil if you planned on changing it in the near future.