Does anyone know of the percentage of synthetic oil thats in castrol 5w30 semi-syn ?

50% syn and dino oil. Mix your own or buy it pre-mixed. I would goe either way with plain old dino oil or full syn.

Just go to Walmart and buy the full syn in a 5 qt jug. Mostly, it is on sale for $23. for M1. Quaker State is less sometimes as low as $20.

Another suggestion if you are not a DIY and don't want to spend $100.00 and 2 hours at a Lexus dealer, is to have your oil changed at a Toyota dealer. They don't serve donuts and lattes or have a Keurig coffee maker, but they will change your oil for less $$. If you look online you may find oil change coupons for $$ off at Toyota dealers. They have your filter and they have your oil be it full synthetic, a blend, or dino. Many don't want to crawl under their car and have oil drip on their face and this is one alternative.

A quart a year seems to me to be well within limits. Why worry about that?

I somewhat agree as the cost of a quart of oil a year isn't a concern. Where my concern is the loss/usage of a quart in 5000 miles . That indicates things have changed and we all know they never get better.

I just changed the oil in the 2013 fSport I bought last April. After dropping over $60.00 for 6qts of 15K synthetic, and filter, I went and looked on line for a visual of where the filter was... Well, I was a little disheartened to see/read I'd need a special tool. Well, I thought I'd check it out before farming it out, and lo-and-behold, my biggest channel locks fit, and it didn't take much to get it loose. After that it all went pretty smooth.