That's an old woman's tale. Almost every motor made in the past 15 years is fully CNC machined, automated assembly, and briefly run-in at the factory. Modern motors have very low blowby and oil use, otherwise the ODB II emissions wouldn't last very long.I was always told not to put Synthetic oil in the engine till everything is well seated. About 30,000 miles or when factory warrenty is up.
If the motor isn't broken in after 2,000-5,000 miles, it never will be.
The exception is HD motors, such as Cummins, Mack, Cat, Detroit Diesel, etc. The motor used in the Dodge Ram HD trucks is a Cummins, and they state to wait 20,000 miles. That motor has nothing in common with the FJ Cruiser
On the other hand, the Dodge Sprinter - made in Germany by Mercedes, uses a 3.0 litre common rail turbodiesel V6. It's factory filled with a synthetic 0W-40. A lot of cars are now factory filled with synthetic oils
I've gone into detail - some forum members would say *painful* detail - about how oil viscosity is rated. A search will uncover this information. Executive Summary: at normal test temp of +100 C, a 0W-30, 5W-30, 10W-30, and SAE 30 will rate 9.3-12.5 cSt. At extended high temp high shear of +150 C, they *must* have a minimum 2.9 mPa s viscosityAlso 0 w 30 here in Florida? Mabe in Alaska but here I think 10 w 40 at least.
I would avoid that 10W-40 s***. That conventional garbage makes heavy use of polymeric additives that will actually cause deposits to form in the motor. Amsoil makes a 10W-40 synthetic that folks swear by, especially for classic factory hotrods as it protects the solid lifters and cam from wear
In other parts of the world, Toyota has a wide range of viscosity for the same motor. For example, although they now suggest a 5W-30 is appropriate beyond +40 C, at one time they had a high temp cutoff of +10 C for a 5W-30
Toyota will recommend oils like 15W-40 as long as the temp is above -10 C. This is a heavy duty diesel oil that provides good service, although Toyota would frown on its use in North America
If you have your heart set on some sort of 40 weight, I use Mobil 1 0W-40 European Car Formula. I have very good used oil analysis results with this oil, and it is specifically approved for ACEA A3, B3/B4 and Opel/BMW LL service: that means in the EU up to 24 months or 30,000 miles before an oil change
Mobil 1 0W-40
This oil won't form deposits, and is quite appropriate to use even at -30 C, which I doubt you would ever see in Florida. What I am unsure about is how Toyota would react if you ever had a warranty claim. In the EU they would probably honor the claim, here they would probably deny it
There is a TSB out from Toyota regarding new factory fill with a synthetic 75W-85 oil on the axles, and to require dealerships to always use this oil from now on.I also plan on using synthetic in the diffs and trasfer case but not till around 15,000 miles so they have time to polish and seat together.
Some of us changed the gear oil early. I did all my gear oil at 1,600 km, the front axle and TC looked clean. Rear axle was already black. I put in Mobil Delvac Synthetic 75W-90
Also an old woman's tale about axles and synthetic oil. A lot of axles are factory filled with synthetic. Apparently, all 2008 TOyota including FJ have synthetic gear oil. Almost all HD trucking axles have synthetic oil, as do most domestic trucks
Here is our discussion of the Toyota synthetic gear oil TSB