{"id":589,"date":"2026-06-23T08:15:35","date_gmt":"2026-06-23T12:15:35","guid":{"rendered":"https:\/\/www.worldsbestdieseloil.com\/oil-guide\/1985-buick-regal-5-7l-8-cyl-diesel-maintenance-guide\/"},"modified":"2026-06-23T08:15:35","modified_gmt":"2026-06-23T12:15:35","slug":"1985-buick-regal-5-7l-8-cyl-diesel-maintenance-guide","status":"publish","type":"post","link":"https:\/\/www.worldsbestdieseloil.com\/oil-guide\/1985-buick-regal-5-7l-8-cyl-diesel-maintenance-guide\/","title":{"rendered":"1985 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

What oil does a 1985 Buick Regal 5.7L Diesel take?<\/h2>\n

The 1985 Buick Regal with the 5.7L 8-cylinder Engine Code [N] requires an oil capacity of 7 quarts<\/strong> (including filter change). Recommended viscosities include 10W-30<\/strong> for temperatures below 16\u00b0C, 15W-40<\/strong> for -18 to 16\u00b0C, and 30 weight<\/strong> for continuous driving above 0\u00b0C. AMSOIL recommends using high-quality synthetic diesel oils like the Signature Series for maximum protection.<\/p>\n

AMSOIL product recommendations<\/h2>\n

Based on the vehicle specifications, here are the recommended AMSOIL products for your 1985 Buick Regal Diesel.<\/p>\n

Engine Oil Recommendations<\/h3>\n
\n\n\n\n\n\n
Product Name<\/th>\nViscosity<\/th>\nProduct Code<\/th>\n<\/tr>\n
AMSOIL Signature Series Max-Duty Diesel Oil<\/td>\n10W-30<\/a><\/td>\nDTTQT-EA<\/a><\/td>\n<\/tr>\n
AMSOIL Signature Series Max-Duty Diesel Oil<\/td>\n5W-30<\/a><\/td>\nDHDQT-EA<\/a><\/td>\n<\/tr>\n
AMSOIL Heavy-Duty 100% Synthetic Diesel Oil<\/td>\n10W-30<\/a><\/td>\nADNQT-EA<\/a><\/td>\n<\/tr>\n<\/table>\n<\/div>\n

Oil Filter Recommendation<\/h3>\n
\n\n\n\n
Product Name<\/th>\nProduct Code<\/th>\n<\/tr>\n
AMSOIL Oil Filter<\/td>\nEAO64-EA<\/a><\/td>\n<\/tr>\n<\/table>\n<\/div>\n

Coolant & Antifreeze Recommendations<\/h3>\n
\n\n\n\n\n
Product Name<\/th>\nProduct Code<\/th>\n<\/tr>\n
AMSOIL Passenger Car & Light Truck Antifreeze & Coolant<\/td>\nANTPC1G-EA<\/a><\/td>\n<\/tr>\n
AMSOIL Propylene Glycol Antifreeze and Engine Coolant<\/td>\nANT1G-EA<\/a><\/td>\n<\/tr>\n<\/table>\n<\/div>\n

Automatic Transmission Fluid (ATF) Recommendations<\/h3>\n
\n\n\n\n\n
Product Name<\/th>\nProduct Code<\/th>\n<\/tr>\n
AMSOIL Signature Series Fuel-Efficient ATF<\/td>\nATLPK-EA<\/a><\/td>\n<\/tr>\n
AMSOIL OE Fuel-Efficient ATF<\/td>\nOTLQT-EA<\/a><\/td>\n<\/tr>\n<\/table>\n<\/div>\n

Engine Oil Specifications & Details<\/h2>\n

Proper lubrication is critical for the longevity of the 5.7L diesel engine. Always verify your current oil level after a refill.<\/p>\n

Oil Viscosity Guide<\/h3>\n
\n\n\n\n\n\n
Temperature Range<\/th>\nRecommended Viscosity<\/th>\n<\/tr>\n
Below 16\u00b0C<\/td>\n10W-30<\/td>\n<\/tr>\n
-18 to 16\u00b0C<\/td>\n15W-40<\/td>\n<\/tr>\n
Above 0\u00b0C (Continuous Driving)<\/td>\n30<\/td>\n<\/tr>\n<\/table>\n<\/div>\n

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

Engine Oil Capacity<\/h3>\n
\n\n\n\n
Condition<\/th>\nCapacity<\/th>\n<\/tr>\n
With Filter Change<\/td>\n7 quarts<\/td>\n<\/tr>\n<\/table>\n<\/div>\n

Note: After refill, always check the oil level manually.<\/em><\/p>\n

Automatic Transmission Fluid Specifications<\/h2>\n

The 1985 Buick Regal uses several different transmission models. The AMSOIL lookup notes that for these applications, the specification has been updated from Dexron II or III to Dexron VI per a manufacturer Technical Service Bulletin.<\/p>\n

Transmission Capacity & Models<\/h3>\n
\n\n\n\n\n\n\n
Transmission Model<\/th>\nInitial Fill<\/th>\nTotal Fill<\/th>\n<\/tr>\n
THM200-4R (4 Speed)<\/td>\n5 quarts<\/td>\n11 quarts<\/td>\n<\/tr>\n
THM325-4L (4 Speed)<\/td>\n3.2 quarts<\/td>\n10 quarts<\/td>\n<\/tr>\n
THM250C (3 Speed)<\/td>\n4 quarts<\/td>\n10.8 quarts<\/td>\n<\/tr>\n
THM200C (3 Speed)<\/td>\n3.5 quarts<\/td>\n9.4 quarts<\/td>\n<\/tr>\n<\/table>\n<\/div>\n

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

Given the historical context of GM V8 diesel engines from 1978\u20131985, owners should prioritize rigorous adherence to fuel system maintenance and cooling system integrity. Monitoring for common failure points associated with this engine architecture is critical for longevity. Because these older diesel designs can be sensitive, verifying the correct grade of diesel-specific lubricants is highly recommended.<\/p>\n

Common diesel oil-related concerns and how AMSOIL products may help<\/h2>\n

Maintaining an older diesel engine requires addressing specific operational challenges through high-quality lubrication.<\/p>\n

\n\n\n\n\n\n
Concern<\/th>\nWhy it matters<\/th>\nAMSOIL Product<\/th>\nHow it may help<\/th>\nLimitation<\/th>\n<\/tr>\n
Engine Wear<\/td>\nDiesel engines face high pressure and friction.<\/td>\nDTTQT-EA<\/a><\/td>\nDelivers up to 6X more wear protection.<\/td>\nDoes not repair existing damage.<\/td>\n<\/tr>\n
Contaminants<\/td>\nSmall particles can cause abrasive wear.<\/td>\nEAO64-EA<\/a><\/td>\n99% efficiency at 20 microns.<\/td>\nRequires regular replacement intervals.<\/td>\n<\/tr>\n
Extreme Temperatures<\/td>\nViscosity changes can affect lubrication.<\/td>\nDHDQT-EA<\/a><\/td>\nExcels in extreme temperatures.<\/td>\nMust match required viscosity grade.<\/td>\n<\/tr>\n<\/table>\n<\/div>\n

Common maintenance concerns for this vehicle<\/h2>\n

Based on NHTSA consumer reports, owners of the 1985 Buick Regal have noted several areas requiring attention:<\/p>\n