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The first impression is that the best way to test a CVT fluid would be to put it in a car containing a CVT transmission, and then verify that it runs without any problem. But in fact, this chassis dynamometer testing method does not allow testing the limits of the fluid. In order to really test these limits, the best way is then to put a CVT between electric motors, and progressively apply load until the limits appear. But going to the limits will weaken the CVT itself, especially the belt. Besides, this testing method is far from simple, requiring a lot of money, fluid, and time. Therefore, it is necessary to find a suitable and simpler testing method that would give some similar results. The idea is then to use some usual tribometers, like the LFW-1.

This communication examines three strategies of predictive lubricant monitoring and replacement, used for farm tractors or similar vehicles. These strategies optimise the draining periodicity. They are the off-line follow-up, the sensors follow-up and the analytical model follow-up. The implementation of the suggested analytical model will be discussed, on the basis of field collected data (on a series of tractors, either customer's or on loan). Regular oil samples, and significant ones carried out at the end of the study, were taken and analysed in order to predict the evolution of the lubricant characteristics. Extensions to the experimental study were carried out at the end of this work. They are discussed in the paper (FZG gear scuffing, 4 ball wear and EP…).

Four polymeric viscosity index improvers [PAMA: poly(n-alkyl methacrylate), EP: (ethylene-propylene) copolymer, HPI: hydrogenated poly(isoprene) polymer and SHB: (styrene-hydrogenated butadiene) copolymer], are studied in cyclohexane, n-heptane and a mineral base oil (130 NS). The hydrodynamic diameter of isolated and aggregated polymers is measured by Dynamic Light Scattering technique. The sample concentrations were always below C* which is the concentration of first overlap separating the dilute regime from the semi-dilute regime. Experiments were run from 20 to 90°C. Our results show that, depending on the chemical nature of the polymer, the solvent and the temperature value, the solute particles are either aggregated (micelles or not) or isolated.