Enter RPO Codes
Separate codes with spaces or line breaks. On 1984-and-newer cars, the full list is on the SPID sticker (glovebox, console lid, or spare tire cover). Older cars: the build sheet or window sticker.
Decoded
LS1 — a Pontiac 455 HO in ’71 and the Gen III
5.7 in ’97) show every meaning; set the model year to surface the right one.
Where to find your RPO codes
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.
Why one code has multiple meanings
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.
Accuracy & sources
The database covers the RPOs most relevant to muscle-era and enthusiast GM vehicles plus common modern drivetrain codes — a few hundred of the many thousands GM has issued. Codes not in the database still decode by letter family (L = engine, M = transmission, G = axle, Z = special package, and so on). 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.