[Cosmo]

I have a 03 Tundra V8 with 1300 miles. I need to make my mind up on synthetic or not to synthetic. I live in Duluth MN so we get temps down to -30 with -20 not uncommon for a few days at a time then it may get up to 0. Summer time it does get into the 90s. It sounds like a 5w30 synthetic would be the way to go but I do not want to screw up my warranty. I do a lot of in town driving so I would normally go with an interval of 3K with non- synthetic oil.
What would be a good interval if I switched to synthetic say Mobile 1 and still not have a problem if I need to use my warranty?
This forum is great. My wife thinks I am nuts for how much time I spend on it.
Thanks all ahead of time.