Leading conventional - Pennzoil
Leading synthetic blend - Castrol Syntec Blend (I would have thought this was Durablend)
Leading synthetic - Mobil 1
Leading high-mileage oil - Valvoline MaxLife
The most popular consumer grades of motor oil are 5w30, 10w30 and 5W-20 in that order from what I have read.
Castrol advertises maximum horsepower longer due to having a HT/HS in 10w30 of 2.92 (IIRC) reducing drag, the only way to beat that is to reduce viscosity and HT/HS to the absolute limits of a 30 weight oil. The sludge busting in GTX is a higher amount of calcium and sodium detergents but it's not really any more than Pennzoil.
Leading synthetic blend - Castrol Syntec Blend (I would have thought this was Durablend)
Leading synthetic - Mobil 1
Leading high-mileage oil - Valvoline MaxLife
The most popular consumer grades of motor oil are 5w30, 10w30 and 5W-20 in that order from what I have read.
Castrol advertises maximum horsepower longer due to having a HT/HS in 10w30 of 2.92 (IIRC) reducing drag, the only way to beat that is to reduce viscosity and HT/HS to the absolute limits of a 30 weight oil. The sludge busting in GTX is a higher amount of calcium and sodium detergents but it's not really any more than Pennzoil.