In May 1998, the HR34, ER34, ENR34, and BNR34 marked the introduction of the more fuel-efficient and environmentally-friendly RB25DET NEO engine. The RB20E engine was discontinued in the R34 base model (GT), and the RB20DE, after last being used in the R32 Skyline, was reintroduced in the updated NEO guise. The R34 GT, powered by the RB20DE NEO and coupled with a five-speed gearbox, became the most fuel-efficient straight-six Skyline to date (of any shape). The 4-speed automatic transmission available on some models was retained, and was upgraded with tiptronic-style manual controls.[43] An export-market 25GT Turbo coupe variant (often abbreviated as GT-T) was sold in Singapore and Hong Kong from 1998 to 2000, while the facelift 25GT Turbo was sold in New Zealand between 2001 and 2002 alongside the GT-R V-Spec. These were the only three countries outside of Japan that sold the R34 25GT Turbo model Skylines new. All Japanese Nissan Prince Store locations that sold the Skyline were renamed Nissan Red Stage.
Nissan introduced two new models for the base vehicle, the 25GT-X and the 25GT-V. The 25GT-X was only available as a sedan and included optional extras over the base-model 25GT and 25GT Turbo such as tinted rear windows and pop-up LCD display that replaced the triple cluster on the turbo models. Another version, the 25GT-V, was a naturally-aspirated variation powered by the RB25DE, came standard with the upgraded 4-piston front and 2-piston rear Sumitomo calipers, limited-slip differential and 17" alloy wheels only found on the turbo models.

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