A conveying belt is disposed so as to guide a recording medium on a side opposite to an image carrying belt across an extension line of a stretch surface formed by a transfer nip and a pressure member. An initialization request to create or extend a file is received. Each of the first blocks is transformed into a plurality of second blocks, any second block under consideration having a second respective number of samples which depends on the resolution of the second block under consideration, and containing samples selected according to their frequency. in dry air, indicating significant thermoxidative stability with minimal or no aromatic content, thereby enabling use of Groups II and III base oils, in particular, without reduced toxicity andor quality concerns as compared with Group I base oil lubricants.