The second-generation Mazda3 (code BL) had the difficult task of succeeding a very successful first iteration (BK). It reuses the platform (shared with the Ford Focus II) but significantly improves rigidity, aerodynamics, and perceived quality. While the petrol engines shine with almost irreproachable reliability, the picture is much more contrasted on the diesel side (MZ-CD and MZR-CD), which accounted for the bulk of sales in Europe. The model benefited from a facelift in late 2011, bringing minor aesthetic touches, better sound insulation, and, above all, a major evolution of the 1.6 diesel block (from 109 to 115 hp) which transformed its reliability. Overall rating: excellent for petrol, very uneven for diesel.
If you are looking for a Mazda3 BL, the golden rule is simple: prioritize petrol. The 1.6 and 2.0 MZR engines are models of reliability that will take you very far without issues. If your annual mileage requires a diesel, avoid the 1.6 MZ-CD 109 hp (before 2011) and be extremely vigilant with the 2.2 MZR-CD (clear service history mandatory, check of the oil strainer and chain). The only rational and recommendable diesel choice is the 1.6 MZ-CD 115 hp (appeared late 2010), which is much more robust and refined.