I just changed my oil and put in some Mobil 1 5w-30 (since thats the viscosity that the manual called for, only Motorcraft brand.). However, I went to the Mobil 1 website and they say my car calls for 5w-20 (98' 3.8). I was afraid that I'd burn oil that had too low of a viscosity so I thought I'd play it safe with the 30 anyway. Is this bad for me? Good for me? Doesn't really matter?