Terminology that is accepted as and commonly used is just fine.
Heaviest, thickest, ... is just fine.
You'll want a 5w30 with an HTHS >=3.5. That'll get you the gnarliest 5w-30. Start with the Euro or Diesel specs, since some require >3.5 HTHS. This means you'll want the Mobil1/Castrol/Pennzoil euro oils, and avoid anything API SP/GF6.
Useable in both diesel and gasoline engines, Shell ROTELLA® T6 Multi-Vehicle Full Synthetic is a synthetic diesel oil providing peak performance and exceptional fuel economy. Learn more this product here.
rotella.shell.com
Discover how Mobil 1™ ESP 5W-30 advanced synthetic motor oil helps prolong the efficiency of emission systems in diesel and gasoline powered automobiles.
www.mobil.com
Pennzoil Platinum Euro Full Synthetic oil is designed for modern light duty diesel and high-performance engines in 0W-20, 0W-30, 0W-40, 5W-30 and 5W-40 viscosities.
www.pennzoil.com
Valvoline European Vehicle Full Synthetic Motor Oil is designed specifically to meet and exceed the demanding requirements of most European gasoline and diesel engine manufacturers. Our exclusive formula uses top wear additives, premium antioxidants and added detergents to fight wear, resist oil...
www.valvoline.com
Castrol® Edge Euro Car is an advanced full synthetic motor oil formulated to improve engine durability in European cars. Find out if you can benefit from switching to Castrol Edge Euro Car formula.
www.castrol.com
Most popular oil for modern road cars and light trucks, as specified for most late-model BMW, General Motors, and Nissan vehicles
www.redlineoil.com
Mobil Delvac 1™ ESP 5W-30 is an advanced synthetic heavy duty diesel engine oil for long and reliable service.
www.mobil.com
Flip a coin.