Picked up a used Toyota Tundra Platinum with a high mileage 5.7L 3UR-FE. This truck has over 150,000 miles going between Arizona and the pacific northwest (snowbird) and looks nearly new. It will *not* be a daily driver; just when I need a truck. Toyota.com online service history shows great dealer service visits, mileage, and dates. Toyota wants 0w20 syn in this four cam motor, and is OK with 5w20 syn with their VVTi system. I changed the oil first time after my new to me purchase and used 8+ quarts (yes it specs 8) Mobil 1 0w20. Those four cams are super noisy with 0w till it warms up...even starting at 70F. It was cold dead silent upon purchase and right up until I changed the oil. It is not uncommon to put 5w30 in these trucks, so that is what I suspect was in it. I live in Idaho, so teens/rarely single digits cold, but not Alaska cold. 5w will flow down to -30C, we likely won't hit -10C, so I got no problem going to 5w20. I will definitely change to M1 5w20 HM next OCI. So here is my question. I want to thicken this brand new 0w20 to cut the cold start noise (and cold start wear). It went from dead silent when cold, to a four cam rattle trap after M1 0w20 was put in (OEM Toyota oil filter). I was thinking STP Synthetic oil treatment or a bit of M1 80w90 gear oil. What say the group?