Oldsmobile Omega — X-body, front-drive (third generation) (1983–1984)

The third-generation Omega was Oldsmobile's front-drive X-body compact: Wikipedia gives a two-door coupe and four-door sedan in standard and Brougham trims, with the sportier ES sedan in 1983, and names the Chevrolet Citation, Pontiac Phoenix and Buick Skylark as its related cars. The NICB VIN manuals list the Omega and Omega Brougham for 1983 and 1984. No GM order guide, data book, Heritage kit or service RPO list for the Omega is in the archive, so only powertrain codes are listed: Wikipedia's Omega article names the LE2 and LH7 V6 codes and describes the Iron Duke four and the automatic transaxle without a code, and the Heritage kit pages of the Chevrolet Citation, the X-body twin, are cited to date the engine codes the two cars share and for the automatic-transmission codes, which no Omega source prints. No source read ties an option, package, paint or trim code to the Omega with a year, so none is listed.

Codes

Engines

Code	Description	Years	Models/Notes	Confidence
LR8	Engine, 2.5 L (151 cu in) L4, throttle-body fuel injection	1983–1984	the four-cylinder; matched to the Omega's unit by meaning: Wikipedia's Omega article names the 2.5 L Iron Duke four-cylinder but prints no code; shared X-body code; cited from the Chevrolet Citation kit, whose engine pages print it with its model year ⛭ GM Heritage — 1983 Chevrolet Citation, p.10 ⛭ GM Heritage — 1984 Chevrolet Citation, p.10	single-source
LE2	Engine, 2.8 L (173 cu in) V6, 2-barrel carburetor	1983–1984	the optional V6; Wikipedia's Omega article names LE2 in its third-generation infobox and engine text and offers it across the generation; shared X-body code; cited from the Chevrolet Citation kit, whose engine pages print it with its model year ⛭ GM Heritage — 1983 Chevrolet Citation, p.10 ⛭ GM Heritage — 1984 Chevrolet Citation, p.10	single-source
LH7	Engine, 2.8 L (173 cu in) V6, high output, 2-barrel carburetor	1983–1984	Wikipedia's Omega article names LH7 in its infobox and says the high-output V6 was offered on the ES; shared X-body code; cited from the Chevrolet Citation kit, whose engine pages print it with its model year ⛭ GM Heritage — 1983 Chevrolet Citation, p.10 ⛭ GM Heritage — 1984 Chevrolet Citation, p.10	single-source

Transmissions

Code	Description	Years	Models/Notes	Confidence
MD9	Automatic transaxle, 3 speed (THM 125)	1984	GM engineering code behind the MX1 merchandising option; matched to the Omega's unit by meaning: Wikipedia's Omega article names the 3 speed TH-125C automatic in its infobox but prints no code; the Citation kit's automatic-transmission weight line for the 2.5 L engine reads "Merchandising Option for MD9, MX1", a remark naming two units, so the year rests on the page's 1984 model-year field and the row stays single-source; 1983 is left out because no listed kit page heads the code that year; shared X-body code; cited from the Chevrolet Citation kit ⛭ GM Heritage — 1984 Chevrolet Citation, p.34	single-source
MX1	Automatic transmission, 3 speed (merchandising code for the THM 125)	1984	matched to the unit by meaning: Wikipedia's Omega article names the 3 speed TH-125C automatic in its infobox but prints no code; the page prints MXI (letter I); 1983 is left out because no listed kit page heads the code that year; shared X-body code; cited from the Chevrolet Citation kit ⛭ GM Heritage — 1984 Chevrolet Citation, p.34	single-source

Sources

Factory documents (T1)

No Oldsmobile factory document for the 1983–1984 Omega is in docs/factory-docs/ or docs/heritage-ocr/. The rows cite the Chevrolet Citation Heritage kits (X-body twin) for shared engine and transmission codes only, on the brief's listed RPO pages (owner, 2026-10-03):

[HK] chevrolet/1983-Chevrolet-Citation.txt — MVMA specifications, 1983, engine description page (p. 10)
[HK] chevrolet/1984-Chevrolet-Citation.txt — MVMA specifications, 1984, engine description page (p. 10) and optional equipment weights (p. 34)

Other sources

https://en.wikipedia.org/wiki/Oldsmobile_Omega — third-generation infobox, body styles, trims, engine and transmission text (retrieved 2026-11-05 as wikitext, action=raw)
NICB Passenger Vehicle Identification Manual, GM sections (T4): docs/reference/nicb/nicb1983-gm.txt p.50 and nicb1984-gm.txt p.50 — Omega and Omega Brougham series names