Diesel Engine Oils Heavy Duty Diesel Engine Oils Best Reliant™ Full Synthetic Engine Oil SAE 5W-30 Reliant™ Full Synthetic Engine Oil SAE 5W-40 Reliant™ Premium Plus 10W-30 API FA-4 Synthetic Blend Better Reliant™ Premium Diesel Engine Oil SAE 15W-40 Reliant™ Premium Diesel Engine Oil SAE 10W-30 Good Reliant™ Heavy Duty Engine Oil SAE 10W Reliant™ Heavy Duty Engine Oil SAE 30 Reliant™ Heavy Duty Engine Oil SAE 40 Reliant™ Heavy Duty Engine Oil SAE 50 Reliant™ Heavy Duty Engine Oil SAE 15W-40, CK-4 PennGrade® Heavy Duty SAE 15W-40 Reliant™ Heavy Duty Engine Oil SAE 10W-30, CK-4 Natural Gas/Bio-Gas Natural Gas / Landfill / Biogas Engine Oils Best Blue Flame HB-10™ Engine Oil SAE 40 Better Blue Flame HB-8™ Engine Oil SAE 40 Good Blue Flame HB-16™ Engine Oil SAE 40