June 1984 marked the introduction of the Lancia Prisma diesel, the marque's first modern diesel-engined passenger car. The diesel was imperative, as more than a third of Italian sales in the Prisma's class were of diesel-powered cars. Its naturally aspirated 1929 cc SOHC four-cylinder had an iron block, aluminium head and indirect injection; it put out 65 PS. The engine had been developed by Fiat, and was also installed in the Fiat Regata DS—although the Fiat lacked some of Lancia's NVH-improving solutions. The diesel engine was light, only weighing more than the 1.6-liter petrol unit. All Diesel Prismas sported a sightly domed hood, needed to clear the taller engine. Some updates were introduced with the diesel, including optional hydraulic power steering, redesigned seats, new striped cloth upholstery and a four-spoke steering wheel.