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1991 Mercury Cougar

Factory specifications, fluid capacities, torque values, EPA fuel economy and the federal safety record for the 1991 Cougar.

Body PASSENGER CAR

The 1991 Mercury Cougar is a passenger‑car built on the platform that defined the model’s late‑generation line, equipped with an engine that requires 4.5 qt of oil and runs on 10W‑30 or 5W‑30 viscosity grades. Across the 1990‑2002 production span the Cougar recorded a modest 93 owner complaints for this year, with the most frequent issues centered on engine and engine‑cooling systems and three manufacturer recalls documented. Compared with the broader reliability record—peaking at 521 complaints in 1999 and dropping to a single complaint in 1998—1991 sits near the lower‑end of the series’ trouble spectrum, indicating a relatively stable year in an otherwise variable reliability history.

Model year200220012000199919971996199519941991

Quick specs

Fluid capacities, tune-up values and fuel economy at a glance.

Engine oil capacity4.5 qtOEM · verified
Engine oil type10W-30 / 5W-30OEM · verified

Fitment & sizes

Replacement part sizes and factory part numbers — battery, bulbs, filters and belts.

OE service part numbers OEM · verified

ThermostatRT1052 discontinued · alt RT1053

Full specifications

Engine, drivetrain, dimensions and economy.

Dimensions & weight NHTSA vPIC

Overall length198.8 in
Overall width72.8 in
Overall height52.8 in
Wheelbase113 in
Curb weight3616 lb
Weight distribution (front / rear)57/43

Service quick specs OEM factory data

Capacities, torques and tune-up values from the factory service manual.

This engine holds 4.5 qt of 10W-30 / 5W-30 engine oil, DOT 3 brake fluid.

Lubricants & capacities

Brake FluidDOT 3
Engine CoolantETHYLENE GLYCOL
Engine Oil10W-30 · 5W-30
Engine Oil Capacity4.5 qt
Engine Oil10W-30 · 5W-30
Engine Oil Capacity4.5 qt

Factory maintenance schedule OEM · verified

Normal service, condensed from the factory interval matrix.

Under the factory schedule, replace the engine oil and filter every 7,500 mi; spark plugs every 60,000 mi; coolant every 30,000 mi. The big-interval services (every 30,000 mi for coolant, and the transmission fluid) are the ones owners most often skip — on a lower-mileage example, assume the original fluids are still in it and check them first.

At 7,500 miTire & Wheel Assembly (rotate)
Every 7,500 miEngine Oil (drain & refill) · Engine Oil Filter (replace)
Every 15,000 miPCV Valve (replace) · Steering Linkage (inspect) · Suspension System (inspect) · Tire & Wheel Assembly (rotate)
Every 30,000 miAccessory Drive Belt (inspect) · Brake Linings (inspect) · Engine Air Filter Element (replace) · Engine Breather Filter (replace) · Engine Coolant System (drain, flush & refill) · Exhaust System Heat Shield (inspect)
Every 60,000 miSpark Plugs (replace)

Reliability & federal safety record

Owner-reported issues, recalls, investigations and service bulletins on record with NHTSA — an unfiltered look at what owners actually experience.

The 1991 Mercury Cougar sits early in the 7th-generation cycle, where complaint volumes were still moderate—93 complaints, nearly identical to the 90 recorded for 1990—before a sharp escalation to 123 in 1992 and a peak of 210 in 1993. Recalls held steady at 3 across these early years, while investigations dropped from 5 in 1990 to 2 in 1991, suggesting fewer federal probes into emerging defects. Technical Service Bulletins (TSBs) rose only slightly to 36 from 33, remaining far below the generation’s later highs of 121 in 1996, indicating that widespread documented fixes had not yet accumulated. The 1991 model’s top complaint areas—engine and engine cooling (17), electrical system (12), and service brakes (11)—mirror common aging-vehicle concerns, but the data does not specify root causes. With 7 fire complaints and 4 crash complaints, the 1991 Cougar avoids the complaint surge of 1992–1993, making it a relatively stable choice within this generation, though a thorough inspection of the engine, electrical, and brake systems is warranted.

3
Open recalls
NHTSA campaigns
36
Service bulletins
Manufacturer communications
2
ODI investigations
Office of Defects Investigation
93
Owner complaints
4 involved a crash · 7 a fire
Owner complaints by model year NHTSA · this generation & adjacent
’90’91’92’93’94’95’96’97’98’99’00’01’02

Owner complaints filed with NHTSA, by component

All 93 complaints on record, top 8 components.

Engine & Engine Cooling17
Electrical System12
Service Brakes, Hydraulic11
Exterior Lighting9
Vehicle Speed Control9
Seat Belts7
Fuel System, Gasoline5
Visibility5

Source: NHTSA Office of Defects Investigation complaint database.

Recalls NHTSA · verified

Showing 2 of 3 campaigns on record for this vehicle.

91V048000Power Train:Automatic TransmissionReported 18/03/1991

THE PARK ROD ASSEMBLY CONTAINS A PARK CAM WITH INADEQUATE SURFACE HARDNESS, WHICH COULD LEAD TO PARK DISENGAGEMENT OR NO PARK ENGAGEMENT WHEN THE LEVER IS PLACED IN PARK. Remedy: REPLACE PARK ROD ASSEMBLY ON AUTOMATIC TRANSMISSIONS.

91V076000Visibility:Windshield Wiper/Washer:MotorReported 06/05/1991

THE NUTS WHICH HOLD WINDSHIELD WIPER MOTOR TO THE WIPER MODULE MAY NOT HAVE BEEN SUFFICIENTLY TIGHTENED AND MAY LOOSEN OR COME OFF. THIS CAUSES CHANGED WIPER PATTERNS, OR THE WIPERS MAY JAM IF TWO OF THE THREE NUTS COME… Remedy: APPLY TORQUE RETENTION MATERIAL TO WIPER MOTOR STUDS AND NUTS AND RETORQUE.

Technical service bulletins NHTSA · verified

Showing 5 of 36 bulletins on record with NHTSA.

BulletinDateComponentSummary
011562001-08-06VisibilitySOME VEHICLES MAY EXHIBIT HEATER CORE LEAKS. *SLC
011572001-08-06Unknown Or OtherINFORMATION REGARDING TRANSMISSION FLUID USAGE CHARTS. *SLC
0023102000-11-13Power TrainSUBJECT REGARDING CONTAMINATION FROM PRIOR TRANSMISSION CONCERNS OR EXCESS WEAR MAY BE…
002132000-10-16EquipmentSUBJECT REGARDING CLIMATE CONTROL - EATC - BLOWER MOTOR CONTROL SERVICE TIPS. *JB
00152000-01-10Power TrainINFORMATION REGARDING THE NEW TRANSMISSION COOLER FLUSHER- SERVICE TIP. *MJS

Common OBD-II trouble codes

The most common OBD-II codes for this vehicle's emissions system. These are standardized SAE J2012 definitions, not vehicle-specific fault reports.

P0420
Catalyst system efficiency below threshold — Bank 1
P0300
Random / multiple cylinder misfire detected
P0171
System too lean — Bank 1
P0455
Evaporative emission system leak detected — large leak
P0128
Coolant thermostat below regulating temperature
P0442
Evaporative emission system leak detected — small leak

VIN tools

Decode factory build data for a specific vehicle by VIN.

VIN
Decode a VIN to confirm the transmission and build data for a specific Cougar. OEM
Build data
Plant, GVWR class, engine and body data for any 17-character VIN.
Recalls
Check open recall campaigns against a specific vehicle by VIN.

Vehicles with shared specs

Find every vehicle that shares this one's battery, bulbs, oil capacity, platform or parts.

Vehicles taking 4.5 qtThermostat RT1052

Reference guides

Cross-vehicle references for the kinds of data on this page.

Vehicle recalls & TSBsOBD-II trouble codesMaintenance schedulesFluid capacities & specs

Frequently asked

How much oil does the 1991 Cougar take?

4.5 qt of ABOVE 0 degrees F 10W-30, BELOW 100 degrees F 5W-30, per the factory manual.

Does the 1991 Cougar have open recalls?

NHTSA lists 3 recall campaign(s) for this model year. Check your specific vehicle by VIN.