{"id":432,"date":"2026-06-12T03:24:30","date_gmt":"2026-06-12T07:24:30","guid":{"rendered":"https:\/\/www.worldsbestdieseloil.com\/oil-guide\/1981-buick-regal-5-7l-8-cyl-diesel-maintenance-guide\/"},"modified":"2026-06-12T03:24:30","modified_gmt":"2026-06-12T07:24:30","slug":"1981-buick-regal-5-7l-8-cyl-diesel-maintenance-guide","status":"publish","type":"post","link":"https:\/\/www.worldsbestdieseloil.com\/oil-guide\/1981-buick-regal-5-7l-8-cyl-diesel-maintenance-guide\/","title":{"rendered":"1981 Buick Regal 5.7L Diesel Maintenance Guide: Oil, Filters & Fluids"},"content":{"rendered":"
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\"AMSOIL
AMSOIL diesel oil guide for trucks, vans, SUVs and diesel engines<\/figcaption><\/figure>\n

For the 1981 Buick Regal with the 5.7L 8-cylinder Diesel engine (Engine Code N), the oil capacity is 7 quarts<\/strong> (including filter replacement). Recommended viscosities include 10W-30<\/strong> for temperatures below 16\u00b0C, 15W-40<\/strong> for -18\u00b0C to 16\u00b0C, and 30 weight<\/strong> for continuous driving above 0\u00b0C. AMSOIL recommends using Signature Series 10W-30 Max-Duty Diesel Oil<\/a> paired with an AMSOIL Oil Filter (EAO64-EA)<\/a>.<\/p>\n

What oil does a 1981 Buick Regal 5.7L Diesel take?<\/h2>\n

The 1981 Buick Regal 5.7L Diesel requires an oil grade of CF. The specific viscosity depends on your operating temperature: use 10W-30 for temperatures below 16\u00b0C, 15W-40 for between -18\u00b0C and 16\u00b0C, or a 30 weight oil for continuous driving above 0\u00b0C.<\/p>\n

AMSOIL product recommendations<\/h2>\n

The following AMSOIL products are specifically listed for your 1981 Buick Regal 5.7L Diesel to assist with routine maintenance and engine protection.<\/p>\n

Engine Oil & Filter Kits<\/h3>\n
\n\n\n\n\n\n
Product Name<\/th>\nCode<\/th>\n<\/tr>\n
Signature Series Max-Duty Synthetic Diesel Oil 5W-30 & Filter<\/td>\nDHDQT-EA<\/a><\/td>\n<\/tr>\n
Signature Series Max-Duty Synthetic Diesel Oil 10W-30 & Filter<\/td>\nDTTQT-EA<\/a><\/td>\n<\/tr>\n
Heavy-Duty Synthetic Diesel Oil 10W-30 & Filter<\/td>\nADNQT-EA<\/a><\/td>\n<\/tr>\n<\/table>\n<\/div>\n

Component Specific Fluids & Filters<\/h3>\n
\n\n\n\n\n\n\n\n\n\n\n
Component<\/th>\nAMSOIL Product<\/th>\nCode<\/th>\n<\/tr>\n
Engine Oil<\/td>\nSignature Series 10W-30<\/a><\/td>\nDTTQT-EA<\/a><\/td>\n<\/tr>\n
Engine Oil<\/td>\nSignature Series 5W-30<\/a><\/td>\nDHDQT-EA<\/a><\/td>\n<\/tr>\n
Engine Oil<\/td>\nHeavy-Duty 10W-30<\/a><\/td>\nADNQT-EA<\/a><\/td>\n<\/tr>\n
Oil Filter<\/td>\nAMSOIL Oil Filter<\/td>\nEAO64-EA<\/a><\/td>\n<\/tr>\n
Coolant<\/td>\nPassenger Car & Light Truck Antifreeze<\/td>\nANTPC1G-EA<\/a><\/td>\n<\/tr>\n
Coolant<\/td>\nPropylene Glycol Antifreeze<\/td>\nANT1G-EA<\/a><\/td>\n<\/tr>\n
Transmission<\/td>\nSignature Series Fuel-Efficient ATF<\/td>\nATLPK-EA<\/a><\/td>\n<\/tr>\n
Transmission<\/td>\nOE Fuel-Efficient ATF<\/td>\nOTLQT-EA<\/a><\/td>\n<\/tr>\n<\/table>\n<\/div>\n

Engine Oil Specifications<\/h3>\n
\n\n\n\n\n\n
Viscosity<\/th>\nTemperature Range<\/th>\n<\/tr>\n
10W-30<\/td>\nBelow 16\u00b0C<\/td>\n<\/tr>\n
15W-40<\/td>\n-18 to 16\u00b0C<\/td>\n<\/tr>\n
30<\/td>\nAbove 0\u00b0C (Preferred for continuous driving)<\/td>\n<\/tr>\n<\/table>\n<\/div>\n

Oil Grade:<\/strong> CF<\/p>\n

Engine Oil Capacity & Torque<\/h3>\n
\n\n\n\n\n
Detail<\/th>\nSpecification<\/th>\n<\/tr>\n
Capacity (with filter)<\/td>\n7 quarts<\/td>\n<\/tr>\n
Oil Drain Plug Torque<\/td>\n30 ft\/lbs<\/td>\n<\/tr>\n<\/table>\n<\/div>\n

Note: Always check the oil level after refilling.<\/em><\/p>\n

How much transmission fluid does it take?<\/h2>\n

Transmission capacity varies by the specific model of the automatic transmission installed in your vehicle. For the THM350, the total fill is 10 quarts with a 3-quart initial fill. The THM250C requires a 10.8 quart total fill with a 4-quart initial fill.<\/p>\n

Automatic Transmission Specifications<\/h3>\n
\n\n\n\n\n\n\n
Transmission Model<\/th>\nTotal Fill Capacity<\/th>\nInitial Fill<\/th>\n<\/tr>\n
THM350<\/td>\n10 quarts<\/td>\n3 quarts<\/td>\n<\/tr>\n
THM350C<\/td>\n10 quarts<\/td>\n3 quarts<\/td>\n<\/tr>\n
THM250C<\/td>\n10.8 quarts<\/td>\n4 quarts<\/td>\n<\/tr>\n
THM200C<\/td>\n9.4 quarts<\/td>\n3.5 quarts<\/td>\n<\/tr>\n<\/table>\n<\/div>\n

Note:<\/strong> The manufacturer’s Technical Service Bulletin indicates that the specification for these transmissions has been updated from Dexron II or III to Dexron VI.<\/p>\n

Cooling System Maintenance<\/h2>\n

The cooling system capacity for this vehicle is 17.4 quarts. Maintaining proper coolant levels and quality is vital for preventing overheating in these older diesel architectures.<\/p>\n

\n\n\n\n
Component<\/th>\nCapacity<\/th>\n<\/tr>\n
Coolant System<\/td>\n17.4 quarts<\/td>\n<\/tr>\n<\/table>\n<\/div>\n

Diesel maintenance notes for this vehicle<\/h2>\n