What oil does a 1981 Buick Century 5.7L Diesel take?
For the 1981 Buick Century with the 5.7L 8-cylinder diesel engine (Code N), the required oil capacity is 5.9 quarts including the filter. Recommended viscosities include 10W-30 for temperatures below 16°C, 15W-40 for -18 to 16°C, and 30 weight for continuous driving above 0°C. AMSOIL recommends using high-quality synthetic diesel oils like Signature Series 10W-30 or Signature Series 5W-30 for superior protection.
AMSOIL product recommendations
To simplify your maintenance, AMSOIL offers complete oil change kits and individual high-performance fluids specifically selected for this diesel engine application.
Engine Oil & Filter Kits
| Kit Description | Includes | Product Code |
|---|---|---|
| Signature Series Max-Duty Kit | 5W-30 Synthetic Diesel Oil & Filter | Kit Selection |
| Signature Series Max-Duty Kit | 10W-30 Synthetic Diesel Oil & Filter | Kit Selection |
| Heavy-Duty Synthetic Kit | 10W-30 Diesel Oil & Filter | Kit Selection |
Individual Component Recommendations
| Component | AMSOIL Product | Part Number |
|---|---|---|
| Engine Oil | Signature Series 10W-30 Max-Duty | DTTQT-EA |
| Engine Oil | Signature Series 5W-30 Max-Duty | DHDQT-EA |
| Engine Oil | Heavy-Duty 10W-30 Synthetic | ADNQT-EA |
| Oil Filter | AMSOIL Oil Filter | EAO64-EA |
| Coolant | Passenger Car & Light Truck | ANTPC1G-EA |
| Coolant | Propylene Glycol Antifreeze | ANT1G-EA |
Engine Oil Specifications
Maintaining the correct oil viscosity is critical for diesel engine longevity, especially when managing temperature fluctuations and heavy workloads.
Oil Viscosity Guide
| Temperature Range | Recommended Viscosity |
|---|---|
| Below 16°C | 10W-30 |
| -18 to 16°C | 15W-40 |
| Above 0°C | 30 (Preferred for continuous driving) |
Oil Grade: CF
Engine Oil Capacity & Torque
| Measurement | Value |
|---|---|
| Capacity (with filter) | 5.9 quarts |
| Oil Drain Plug Torque | 30 ft/lbs |
Note: Always check the oil level after refilling.
Automatic Transmission Fluid Specifications
The 1981 Buick Century uses various 3-speed automatic transmissions. Note that manufacturer technical service bulletins have updated specifications for these units.
Transmission Capacity & Specs
| Transmission Model | Total Fill | Initial Fill |
|---|---|---|
| THM250C | 10.8 quarts | 4 quarts |
| THM200C | 9.4 quarts | 3.5 quarts |
| THM350C | 10 quarts | 3 quarts |
| THM350 | 10 quarts | 3 quarts |
Important Note: The AMSOIL lookup note indicates that for these transmissions, the specification has been updated from Dexron II or III to Dexron VI per a manufacturer Technical Service Bulletin.
Recommended ATF Products
| Product Name | Part Number |
|---|---|
| Signature Series Fuel-Efficient Synthetic ATF | ATLPK-EA |
| OE Fuel-Efficient Synthetic ATF | OTLQT-EA |
Coolant Specifications
Proper cooling system maintenance prevents overheating and protects internal engine components from corrosion.
| Measurement | Value |
|---|---|
| System Capacity | 17.4 quarts |
AMSOIL Coolant Options:
- Passenger Car & Light Truck Antifreeze & Coolant (ANTPC1G-EA): 50/50 pre-mix, OAT formulation.
- Propylene Glycol Antifreeze and Engine Coolant (ANT1G-EA): Concentrated (requires mixing with distilled or high-quality water).
Common diesel oil-related concerns and how AMSOIL products may help
| Concern | Why it matters | AMSOIL Product | How it may help | Important Limitation |
|---|---|---|---|---|
| Engine Wear | Diesel engines face high pressure and friction. | Signature Series Diesel Oil | Delivers up to 6X more wear protection. | Requires proper service intervals. |
| Contaminants | Small particles can cause abrasive wear. | AMSOIL Oil Filter | 99% efficiency at 20 microns; greater capacity for small contaminants. | Filter must be replaced regularly. |
| Extreme Temperatures | Viscosity changes can affect lubrication during startup or heavy use. | Signature Series Diesel Oil | Excels in extreme temperatures and maintains proper viscosity. | Select correct grade for ambient temp. |
Diesel maintenance notes for this vehicle
Owners of the 1981 Buick Century diesel should focus on specialized maintenance routines required for engines of this era. Key areas include maintaining fuel system cleanliness and ensuring glow plug functionality. Additionally, given the age of these vehicles, monitoring cooling system integrity, vacuum lines, and fuel delivery systems is highly recommended to ensure reliable operation.
Common maintenance concerns for this vehicle
Based on available research, owners should be aware of the following:
- Cooling System: Monitor for leaks or degradation of hoses and gaskets.
- Fuel Delivery: Diesel engines require clean fuel; consider using additives to maintain injector health.
- Brake Systems: Historical owner reports have mentioned issues with rear wheel brake cylinders causing lock-ups. While these are unverified reports, regular inspection of hydraulic service brakes is advised.
Recall, TSB, and manufacturer communication notes
NHTSA research identified three recalls for the 1981 Buick Century:
Disclaimer: Always verify open recalls by using your specific VIN through official manufacturer or NHTSA channels.
About this vehicle
The 1981 Buick Century represents a unique era in Buick’s history, marking the transition of the Century nameplate from full-size luxury to mid-size offerings. This specific model is characterized by its 5.7L 8-cylinder diesel engine (Engine Code N), occupying a niche within the classic American mid-size lineage.
During this period, the Century was available in various body styles, including coupes, sedans, and station wagons. While these vehicles were designed for versatile use—ranging from daily commuting to family transportation—the diesel variant requires specialized attention compared to gasoline models. Owners often research maintenance routines specifically focused on fuel system cleanliness and cooling system integrity due to the unique requirements of mid-size diesel engines from this era.
Because this vehicle is a classic model, owners should prioritize the inspection of aging components such as vacuum lines and fuel delivery systems. For precise technical performance data or specific engine specifications not covered in general maintenance guides, consulting a dedicated service manual is recommended.
Common questions about this vehicle’s diesel oil and maintenance
How much oil does my 1981 Buick Century Diesel take?
The 5.7L diesel engine requires 5.9 quarts of oil when performing a change that includes the filter.
What is the correct oil viscosity for my diesel engine?
Viscosity depends on temperature: use 10W-30 below 16°C, 15W-40 between -18 and 16°C, or 30 weight for continuous driving above 0°C.
Can I use Dexron III in my automatic transmission?
The AMSOIL lookup note indicates that the manufacturer has updated this specification to Dexron VI via a Technical Service Bulletin.
What should I do if I am towing with this vehicle?
For heavy-duty use, AMSOIL recommends products like Signature Series ATF, which is designed to withstand the rigors of heavy towing and elevated temperatures.
How often should I change my oil filter?
While specific intervals depend on driving conditions, using a high-capacity filter like the AMSOIL EAO64-EA can help manage contaminants and extend service life.
How do I check for active recalls on my Buick?
You should always verify open recalls by providing your specific Vehicle Identification Number (VIN) to a certified Buick dealer or via the NHTSA website.
Disclaimer: Information provided is based on available source data. Always consult your original manufacturer’s service manual to ensure compatibility and correct specifications for your specific vehicle.