xjokerz

I've had no issues using conventional oil and doing the changes every 5k miles with new filter. I'd feel safer every 5k miles than stretching it to 10k, even if I used the best synthetic. There are now oils that allow up to 20k, which is crazy. I wouldn't ever go near that.

tolian21

Es350 is likely to be fine using 10k OCI for most peiple, its not a direct injection engine. as I said before, I tested my oil several times at 10k mark, and it was in excellent shape. Lab even recommended 15k next OCI!
I would be more concerned with newer type of toyota engines, there 5k is more appropriate.