diff --git a/src/SimNDT/core/simulation.py b/src/SimNDT/core/simulation.py
index c21bea2..3d67ccd 100644
--- a/src/SimNDT/core/simulation.py
+++ b/src/SimNDT/core/simulation.py
@@ -70,6 +70,17 @@ class Simulation:
         elif self.Order == 4:
             self.dt = self.TimeScale * np.float32( 0.48 * self.dx / (	 np.max([V]) ) )
 
+        if self.preferredDX is not None:
+          if self.preferredDX<self.dx:
+            self.dx=self.preferredDX
+          else:
+            print("!! Warning: Preferred dx is greater than minimum",self.preferredDX,self.dx)
+        if self.preferredDT is not None:
+          if self.preferredDT<self.dt:
+            self.dt=self.preferredDT
+          else:
+            print("!! Warning: Preferred dt is greater than minimum",self.preferredDT,self.dt)
+
         self.TimeSteps = round(self.SimulationTime/self.dt)
         self.t = self.dt*np.arange(0,self.TimeSteps)