hello everyone.. i have a 1990 chevrolet K1500 scottsdale with a 305 5.0L. my truck says to use 5w30 motor oil and i allwasy have. i swiched over to full synthetic last month and my truck has 119,000 on her.. she burns about 1 qt every 3week. i was just on the mobil 1 web site and they have this motor oil called Mobil 1 0W-30 Advanced Fuel Economy that says it saves fuel miles and all that.... now my question is..it only comes in 0w30..is that safe for my trucks engine?? will it help it to run better..smoother..and protect it?? or is using a different weight going to harm my engine..