For this type of generalized question “what is the best motor oil” it all comes down to the fact there is really no best motor oil “per say”.
It depends on each individual application and needs, but to start, check your owners manual first to find out what the manufacturer recommends as far as (20w-50 etc.) or a single grade motor oil (30w, 50w etc.) and the category (SM, SL, SJ for gasoline engines and CJ-4, CI-4, CH-4 for diesel engines). Refer to the API motor oil charts in our post “Best Motor Oil”
After you have found that information there are three different kinds of motor oil, conventional motor oil or in other words straight refined petroleum motor oil, synthetic blend motor oil which is a blend of synthetic base stocks and petroleum base stocks blended together to make synthetic blend motor oil and then there is 100% synthetic motor oil.
Good quality conventional motor oil or top name brand conventional motor oil can probably run at the outer most 5,000 miles under normal driving conditions. You don’t necessarily need to change it at 3,000 miles unless your doing some hard driving or you have subjected your engine to abnormally harsh conditions. For more information on the 3,000 mile oil change that some oil change centers try and sell you, read our post about: Auto Repair Costs and the 3,000 Mile Oil Change
Some top name brand synthetic blend motor oils should go 7,500 miles or a little more before you need to do an oil change. Again, it depends on the driving conditions you have subjected your engine to and what the motor oil manufacturer recommends.
Most top name brand 100% synthetic motor oils will generally go 10,000, 15,000 or even 25,000 miles before you need to change the motor oil. You will no doubt need to cnges, (Refer to your owners manual) but that is one of the benefits of using 100% synthetic motor oils. You will save money over using conventional motor oil and synthetic motor oil has been tested to be as good if not better in most cases, for your engine. If you have a sound engine, no significant oil leaks and no significant motor oil consumption you just might want to give 100% synthetic motor oil or synthetic blend motor oil a try. Just about, if not all motor oil manufacturers have a guaranty that they will stand behind on they’re motor oil, be it conventional motor oil or synthetic motor oil, just read the fine print.
To further help you make a definitive choice on what is the best motor oil to use please read our post on oil analysis: What Is Your Engine Oil Telling You