There is no danger mixing synthetic and conventional motor oil; however, conventional oil will detract from the superior performance of synthetic oil. read more
So, adding regular oil to your special synthetic oil will mean you'll need to get your oil changed sooner than you would have otherwise. If you have a high-performance engine, it's possible it will be displeased if the (expensive) additives can't work the way they are supposed to. read more
Synthetic oil has a number of advantages over regular oil that can help extend engine life. However, the cost of synthetic oil makes many consumers want to mix it with more inexpensive conventional oil. read more
There is no danger mixing synthetic and conventional motor oil; however, conventional oil will detract from the superior performance of synthetic oil and reduce its benefits. The detailed answer: With synthetic lubricants continuing to grow in popularity, the question of whether synthetics and conventional oils can be safely mixed often arises. read more