This chapter examines R&D dynamics in environmentally friendly vehicle (EFV) technologies—covering conventional internal combustion engine vehicles (ICEV), hybrid vehicles (HV), electric vehicles (EV), and fuel cell vehicles (FCV)—through LMDI-based patent decomposition analysis across IP5 offices from the 2000s to the 2020s. Patent data confirm a fundamental transition from ICEV optimization toward electrification: EV technology’s share rose from below 30% to over 50% at most offices by the 2020s, while ICEV shares contracted across all regions. The PRIORITY effect for ICEV was consistently negative and for EV consistently positive at most offices, signaling an irreversible strategic reorientation. However, national pathways diverged markedly. China’s explosive CNIPA growth was driven by the SCALE and ENVIRONMENT effects, but the 2010s–2020s saw a notable PRIORITY reversal—shifting positive for ICEV (redefining advanced engines for plug-in hybrids) and negative for pure EV. The United States and Europe shared a clear ICEV-to-EV strategic pivot, driven respectively by policy incentives and regulatory pressure including the Volkswagen Dieselgate scandal. Japan alone exhibited persistently negative SCALE effects across all periods, with a weakening EV PRIORITY effect reflecting a diversified “full lineup” strategy spanning hybrids, PHEVs, and FCVs. South Korea pursued a leapfrog approach directly from ICEV to battery EVs, underpinned by its globally competitive battery manufacturing sector.