Akai00

2006 IS250 w/173k. Typical oil change has been 0w20 full synthetic. After the recent change I noticed they put 5w30 & I also had a battery disconnect last week but have put on 50+ miles since then. At idle you can hear in the cabin what I can only accurately describe as a truck or diesel idle. Car sounds find when driving. Any ideas? Hoping not the carbon build up issue as I've got 100k problem free miles out of this vehicle. *Maybe my time is up lol