15 is thicker oil and for bigger engines.
Viscosity and additives.
10W30 would be used in cold climate. 10W40 would be used in hot climate. 30 and 40 means the thickness viscosity when warmed up.
Only the weight of the oil, 20w 40 is thiker than the 15w40, 20w 40 is the best oil for the old cars although 15w40 is very easier cold start ...
Yes, you can mix conventional oil with synthetic oil with no problem.
0W40 is thinner oil made for the tolerances of the Porsche motor. the bearing clearances will not allow proper flow if 10W40 is used and premature wear will occur.
Check owner's manual. If you don't have one copy and paste link below; www.fleet.ford.com/maintenance/owners_manuals I always like using Castrol 10W40 I would recommend ford motor oil,10w40,or ford super duty oil,15W40,this heavy oil is suitable for all gas,and diesel engines.
There is no difference between the term "motor ship" and the term "motor vessel." The two are commonly used interchangeably.
Use only the weight recommended by Volvo and I doubt that they recommend 10w40.
Yes, I used it today.