AlFakher

Purchased used with 72k miles, previous owner did oil changes at Lexus so I'm assuming that they used regular instead of synthetic.

I have a ton of 5w30 synthetic from my previous car, and a couple questions:

Does synthetic help with the carbon buildup issues?

How long will the stock filter hold up with synthetic (did 7.5k with my last car)

KillaIS250

iTrader: (1)

Well the general consensus is that Synthetic oil will help reduce carbon build up. I personally have been running synthetic always and still had the carbon build up issue, so it at best it helps delay the issue. And yeah the OEM filter is recommended for up to 7,500 miles. If you want to keep running the synthetic oil longer than that, just change the filter at 7,500 miles and you should be good. Some member's here have done 10-15k miles on synthetic oil without issues this way.

CLIS250

iTrader: (4)

have run synthetic 5w30 since my first oil change and now at 37k. no issues.

chase350

iTrader: (2)

Can't go wrong with fully synthetic. I used it on my old is300 and it had 200,000.