I have here big variability, about 30%.
For me, typically within a few % with MbTimer(). Under the hood it's QPC.
Don't forget the first load is always way off, but once the file is in the disk cache, timings should be very consistent. Which timer are you using?
Here is an example using a for loop:
Loading 43123 rows took 0.0259 seconds with Recall
Loading 43123 rows took 0.
0274 seconds with Recall
Loading 43123 rows took 0.0268 seconds with Recall
Loading 43123 rows took 0.0269 seconds with Recall
Loading 43123 rows took 0.0263 seconds with Recall
Loading 43123 rows took 0.0264 seconds with Recall
Loading 43123 rows took 0.0259 seconds with Recall
Loading 43123 rows took 0.0261 seconds with Recall
Loading 43123 rows took 0.0257 seconds with Recall
Loading 43123 rows took 0.0258 seconds with Recall
Loading 43123 rows took 0.0252 seconds with Recall
Loading 43123 rows took 0.0261 seconds with Recall
Loading 43123 rows took 0.0249 seconds with Recall
Loading 43123 rows took 0.0247 seconds with Recall
Loading 43123 rows took 0.0246 seconds with Recall
Loading 43123 rows took 0.0246 seconds with Recall
Loading 43123 rows took 0.0242 seconds with Recall
Loading 43123 rows took 0.0243 seconds with Recall
Loading 43123 rows took 0.
0239 seconds with Recall
Loading 43123 rows took 0.0239 seconds with Recall