I'm thinking I can use either SL or SM. It appears the SN only came out in 2011. My problem is I can't get an SM from my current supplier and I'd like to stay with SL if possible.
I've been use Mobil 1 SN in all four of my Toyotas ranging from 98 to 08 currently. None of your cars would need the greater zinc levels found in older oils and as I understand the rating system oil quality improves as you go from SL to SN.
Use whatever is on the shelf in the specified viscosity. Probably SN. No sense overthinking what oil to use.Probably required SM given the build year. You can use SN.
We own a 2004 Highlander with a 3.3L. Vehicle has 295K miles. In 13 years we've thrown any and all 5W30 and it runs like a top. In fact, have 0W30 M1 in there at the moment. My two cents, get what makes you feel good and drop it in.