Ireland used to be a diesel country. Not in a vague, directional sense. In a hard, numerical, seven-out-of-ten-new-cars sense. In 2016, diesel accounted for 70% of all new passenger car registrations in Ireland. By 2024, the share had dropped to 22.80%, and in 2025 it fell again to 17.09%, on SIMI's year-end releases. In absolute numbers, diesel registrations fell from roughly 100,000 units in 2016 to roughly 28,000 in 2024. Understanding why it happened matters for understanding where the market goes next.
How Diesel Got to 70%
The rise of diesel in Ireland was a policy-driven phenomenon. In 2008, the government restructured Vehicle Registration Tax (VRT) and motor tax to be based on CO2 emissions per kilometre rather than engine size. Diesel engines, which produce less CO2 per kilometre than equivalent petrol engines, suddenly became cheaper to tax. Overnight, the economic incentive flipped. Buyers who might have chosen petrol found that diesel was cheaper to run, cheaper to tax, and delivered better motorway fuel economy. By 2016, diesel held 70% of the new car market.
What Went Wrong
Three things converged. First, the Volkswagen emissions scandal broke in September 2015. While its immediate market impact was small, the long-term narrative damage was severe. Diesel went from being the "smart" choice to the "dirty" choice in public perception. Media coverage of NOx pollution, particulate matter, and city-centre diesel bans across Europe reinforced this shift relentlessly.
Second, the introduction of the WLTP (Worldwide Harmonised Light Vehicles Test Procedure) testing regime in 2018 and 2019 changed the CO2 ratings for many diesel models. Under the older NEDC test cycle, diesels looked very clean on paper. Under WLTP, which is more realistic, their advantage shrank. Many diesel models saw their official CO2 figures rise, pushing some into higher tax bands and eroding the financial case for diesel.
Third, hybrid alternatives arrived. Toyota's hybrid lineup offered similar or better real-world fuel economy to diesel without any of the reputational baggage. Petrol-hybrid models went from a marginal share in 2016 to 20.92% of the market in 2024. For many buyers, hybrid was simply a less complicated choice.
The Year-by-Year Collapse
SIMI's year-end releases give the series. Diesel share: 70% in 2016, 54% in 2018, 47% in 2019, 43.29% in 2020, 33.44% in 2021, 26.77% in 2022, 22.16% in 2023, 22.80% in 2024 and 17.09% in 2025. The only pause came in 2024, when diesel's share edged up by about half a point as electric registrations fell, before the decline resumed in 2025 (SIMI, 2 January 2026).
Is Diesel Dead?
Not quite. Commercial vehicles and larger SUVs still skew heavily diesel, and the used car market remains flooded with diesel stock. But for new car sales, the direction has been one way for a decade, and several manufacturers have scaled back diesel engine development for passenger cars. In SIMI's April 2026 release diesel was 12.96% of the year's new registrations (SIMI, 1 May 2026). If that pace holds, AutoNergy's own projection is that diesel stays under 15% in 2027 and becomes concentrated in a handful of large vehicle segments.
See the full diesel-to-electric transition visualised on AutoNergy. The Electric Cars streamgraph shows exactly how diesel's share was absorbed by hybrid, PHEV, and battery electric powertrains year by year.
Source: SIMI, 2 January 2025 and earlier SIMI year-end releases.