Computed by stonks: nominal WTI spot price (series wti-crude-oil-price) deflated by US CPI-U (series us-cpi) to constant 2025 dollars. Real value = nominal × (2025 average CPI ÷ CPI at or before the observation date). The CPI alignment is a step lookup (most recent CPI observation on or before each price date) — never interpolated. Fixed 2025 base year, chosen so the series never re-vintages on every new CPI release.