I went to Infiniti for an oil consumption test a week ago and it turns out my warranty expires a week before I got there so I paid for an oil change. The previous oil in my car was 5W30 and I noticed they put in 10W30, after so it seems as if my slow got really sluggish and doesn't want to accelerate like it use to. Should I assume it's the oil and flush it out and go back to 5W30 or should I just go with a 0W30? Any information is helpful, thanks!

 

For oil, there is one viscosity when the oil is cold, and one when it is warm. The number before the W is the cold viscosity, and number after the W is the warm viscosity.

Therefore, 5W30 and 10W30 are essentially the same once the engine is at operating temperature. The cold start viscosity really isn't important until your car has high mileage and if you live in an area where you encounter freezing temps.

If you see really cold temperatures you want a lighter cold viscosity or else your oil will be like tar on a cold start, which is not good for lubrication.

Conversely, if you have an old motor and everything has "loosened up" a bit you want a heavier oil to fill in the gaps, so to say, while the engine is cold, since everything is no longer tight until the engine warms up and things have expanded.

So unless it's often below freezing where you live, it shouldn't make a difference.