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In spite of the relevance of Classical Cepheids as primary distanceindicators, a general consensus on the dependence of the Period-Luminosity (PL)relation on the Cepheid chemical composition has not been achieved yet. Fromthe theoretical point of view, our previous investigations were able toreproduce some empirical tests for suitable assumptions on the helium to metalrelative enrichment, but those results relied on specific assumptionsconcerning the Mass-Luminosity relation and the efficiency of the convectivetransfer in the pulsating envelopes. In this paper, we investigate the effectsof the assumed value of the mixing length parameter l/Hp on the pulsationproperties and we release the assumption of a fixed Mass-Luminosity relation.As a whole, we show that our pulsation relations appear fully consistent withthe observed properties of Galactic and Magellanic Cloud Cepheids, supportingthe predicted steepening and brightening of the PL relations when moving frommetal-rich to metal-poor variables. Moreover, we show that the distancesinferred by the predicted PW relations agree with recently measuredtrigonometric parallaxes, whereas they suggest a correction to the values basedon the Infrared Surface Brightness technique, as already found from anindependent method. Finally, also the pulsation metal contents suggested by thepredicted PW relations appear in statistical agreement with spectroscopic[Fe/H] measurements.

Classical Cepheid Pulsation Models. XI. Effects of convection and chemical composition on the Period-Luminosity and Period-Wesenheit relations