RPO Decoder

1984 and newer: every car and truck carries a white Service Parts Identification label listing all RPOs — check the glovebox, console lid, trunk lid, or spare tire cover. Pre-1984: RPOs live on the build sheet (often stuffed above the gas tank, under carpet, or behind seat springs), the original window sticker, or dealer invoice. GM cowl/trim tags mostly carry body, paint, and trim data — not the option list.

The 3-character alphanumeric system took its familiar form in the early ’60s and is still in use today — this tool focuses on 1963–2017 but decodes the letter families of any era.

GM recycled RPO codes across decades and divisions. L78 is the 396/375 hp big block at Chevrolet but a 400 4-bbl at Pontiac. L67 is Ram Air IV in 1969 and a supercharged 3800 V6 in 1999. LS6 is the legendary 454/450 in 1970 and the 405 hp Z06 5.7 in 2002. When a code has several lives, this decoder lists them all — set the model year and the era-correct meaning leads while the others are noted below it.

Three data tiers back this decoder. The curated database covers the RPOs most relevant to muscle-era and enthusiast GM vehicles plus common modern drivetrain codes, with hand-checked year ranges. Codes beyond it fall through to a 1967–1986 Chevy/GMC list (including 2-digit paint and 4-character interior trim codes) and then to the full GM parts catalog of 16,000+ RPOs. Catalog entries carry GM's raw description text and no year ranges — codes were reused across decades, so treat multi-meaning catalog results as candidates, not certainties. Entries marked verify have thin or conflicting documentation — confirm against the build sheet, dealer invoice, or a marque registry before restoring or advertising a car.

Not affiliated with General Motors; Chevrolet, Pontiac, Oldsmobile, Buick, GMC and related marks are trademarks of their owner.