I have a 1998 Toyota PU , 4 cyl. It uses 10-30 wt oil. My 2003 Toyota car ( V-6 ) calls for 5-30 wt oil. Is there really that much difference? Can I run 10-30 in my later model 2003 Toyota. The PU has 44,000 original miles ( not driven much ), & the 2003 Toyota sedan has 105,000 miles. Both in excellent condition. I have had no problem getting synthetic oil, which has been all that I have used. Just in case oil gets hard to come by, is why I'm asking, from some one more informed on the subject than me.