Myths about synthetics 2
From Mobil1, AMSOIL and Quaker State....
Can different synthetic motor oils be mixed together?
Mobil 1 is fully compatible with conventional motor oils, semi-synthetic motor oils and other synthetic motor oils, should it be necessary to mix them. However, it is important to note that the superior performance of Mobil 1 will be reduced by diluting it in any way.
AMSOIL XL 5W-30 Synthetic Motor Oil is compatible with conventional petroleum oils. However, AMSOIL does not recommend using a mixture of oil and conventional oils for 7,500-mile or six-month drain intervals. Engine oil additives are not recommended for use with AMSOIL oil.
Another myth...
You can't switch from synthetic oil to conventional oil or vice versa.
You need to start with a synthetic blend for a few oil changes before moving to full synthetic oil. Once you start using synthetic motor oil you cannot go back to conventional oil. Synthetic and conventional engine oils can't be mixed, or else they react and cause engine problems.
Fact
As long as the synthetic motor oil product and conventional motor oil product meet the viscosity and performance requirements outlined in the vehicle’s owner’s manual, you may interchange them with each other.
More myth...
Engines have to be “broken in” before using synthetic oil.
I need to break in my engine with non-detergent oil.
If I use regular oil or synthetic oil in a new engine, my engine will take longer to break in.
Fact
It was common years ago for engine manufacturers to recommend non-detergent oils for engine break-in. This was when the pistons used cast-iron “square-faced” rings and the rings needed to wear some to “seat” into the engine. With today’s technology of oils and engine manufacturing, engine manufacturers no longer recommend the use of non-detergent oils for the break-in period. In fact, engines today are factory-filled with high quality API SL performance motor oil, which contains high levels of detergents and dispersant additives.