 Complete the following phrase:  For the 1959 Formula One season the works cars were finally upgraded to the full 2.5-litre specification, and mechanical upgrades had been made to improve reliability. In addition to the works team, Lotus 16s had also been sold to a number of privateer entrants. As the season progressed the works cars were gradually developed still further, and their qualifying times began to fall. Reliability was still a major issue, however, and too often the cars failed to complete a full race distance. Although regular works driver Hill failed to finish even a single race during the season, his team-mate Innes Irelands car held together long enough to take five World Championship points, with fourth place in the Dutch Grand Prix and fifth in the season finale in the 