I dont know that you have a problem. This does not normally occur. However, with that said here are a couple of scenarios whereby the loss of oil may temporarily occur. I dont know whether your motor is leaking oil or burning oil, to cause a loss from the crankcase sump.
In oil leak situations, such as front or rear main seal leaks, sometimes the leak will get worse, while the cleaning is occurring. Once the shaft and seal are clean, it does take some miles for the seal to find its original memory and create and adequate seal. Or perhaps there is an uneven build up of contaminant on the crank seal. Then the seal will weep some until it has been cleaned completely around the circumference.
In oil burning situations, oil is either slipping past the piston rings, or it is passing buy the valve stem seals. It is highly unlikely that new oil burning would be due to rings. In almost all cases piston rings and lans are cleansed completely with 500 miles of driving during the cleaning phase. This is due to the high heat and pressure created in this part of the motor. The more likely place for new oil burning to occur would be partially cleaned valve stem seals. Although there is plenty of heat generated in this area of the motor, the oil flow is not great. Or in many cases the valve stem seals have been operating with a sizeable layer of contamination encasing them for some time. So in essence the seal has been compressed by debris within the valve guide. Once again it will take some driving to have the seal rebound.
It is possible that a short distance into the rinse phase, sizeable amounts of contaminates have already been driven to the filter, possibly from corners of the oil pan, now creating more space in the system.
How much oil is the car using? Do you know whether its is leaking or burning? Tell us what make and model and mileage. Hopefully, the above information is helpful to you. Please feel free to fire off any further questions you may have.
Best Regards,
Rich Eklund Auto-Rx Worldwide, Inc. Chemical Consultant
