15w40 is thicker at all temps vs 10w30.
The weight of the oil when it is cold. The 15w is a thicker oil than the 10w when it is cold.
15w-40 in summer and 10w-30 in winter
15w/40 - recommended 10w/30 - satisfactory
The recommended oil for a Ford 300 is Shell Rotella 15w-40. If cost is an issue, regular 10w-30 or 10w-40 oil can be used.
15w means they are the viscosity (flow) when the oil is cold, the -30 and -40 is the viscosity of the oil when hot. Therefore the 15w-30 being the lower Viscosity means it will flow fast then the 15w-40 when the oil is hot.
Viscosity. 5W-30 is a "thinner" oil than 10W-40 is.
I like to run 15w-40 rotella or dello or 10w-30
10W/30 ILSAC GF2 or use SG,SH,SJ 20W/50 or 15W/40
Suzuki recommends the use of SUKUZI PERFORMANCE 4 MOTOR OIL, or an oil which is rated SF or SG under the API classification system. The viscosity should be SAE 10w-40 if a 10w-40 isn't avalible 10w-30, 10w-50, 15w40, 15w-50, 20w-50 can be used depending on the temprature. I would stick to 10/15w 40/50 to be safe.
An NPR diesel uses a 15w-40 weight oil in most applications. Gas engines use 10w-30.
Depends on whether it's a gas or diesel engine. 10W-30 for a gas engine should suffice, while 15W-30 or 15W-40 oil which meets API-CJ4 standards would be what you'd want for a diesel.
The 10W 40 oil is thicker and is thought by many to be more efficient.