I have a 2003 honda civic i have used penzoil oil?

The last 11 years could I change to a different brand like mobil? Same weight of course

It doesn't matter what engine oil you use.

The brand means nothing.

I can use both Castro 5W-20 oil or Mobli 1 Oil 5W-20 since its the same type of oil.

I can fill half the engine with Mobil 1 5W-20 and another half with Formula 1 5W-20 and nothing will happen to the car engine.

Remember to check the oil dip stick.

Sure can. Or, you could two of X oil & two of Y oil & one of Z oil. You can mix brands & weights if you want.

Sure you can change to mobile if you want to but what, s wrong with pennzoil? I used pennzoil for over 30 yrs. And never had any trouble with the engines! My Buick i use high mileage pennzoil in it! But yes you can change to mobile if you want to!