Keep in mind, the dealer uses whatever they get a good deal on. My mechanic is a 20 years Toyota Master and told me this. He's been in many dealerships.What would be considered too late to switch to synthetic. I was under the impression that the ISF used synthetic from the factory, but when I had the dealer do my 10,000 mile service yesterday, they put in conventional. Would switching to synthetic at my 15,000 mile oil change be too late? Thanks in advance.
As long as you break in the engine nice and easy, you can switch to synthetic at anytime after the first oil change.
If you do switch, stick with it.