The invention relates to systems and methods for accurately compensating for a change in the amount of unwanted fluid diluted in engine oil resulting from a recent long trip. A system, for use in accounting for an effect of a long-trip cycle on remaining life of engine oil, is used in a vehicle, using a long-trip rebate value. The system includes a computer processor and a non-transitory computer-readable medium that is in operative communication with the processor and has instructions that, when executed by the processor, cause the processor to perform various operations. The operations include determining a long-trip time indicating an amount of time that the vehicle was operated recently in the long-trip cycle. The operations further include determining the long-trip rebate according to a rebate function using the determined long-trip time.