finally found the 5w-20 TSB...

[sbergman27]

OK. I have a theory about this odd TSB in which they announced intentions which, 4 years later, they never seem to have acted upon. I ran into this interesting UOA on the BITOG site for a 2007 Yaris factory fill at 1100 miles:

http://tinyurl.com/yjpnz4y

Note the 100C cSt value of 7.9

And then refer to this chart and table:

http://tinyurl.com/qqldw

This factory fill was clearly an Xw20 oil.

So my theory is that they want the EPA to test the car with Xw20 oil, to get slightly better numbers. But just doing a factory fill with that, without clearing Xw20 for use by owners is likely not kosher with EPA policies, so they had to OK it somewhere. But... they really would prefer that most warrantied cars use the 5w30 for superior protection. So... they OK'd 5w20 in the least conspicuous place possible, an obscure TSB, while leaving the 5w30 recommendation in the owners manuals and on the filler caps.

Sound reasonable?

-Steve

[1stToyota]

Originally Posted by sbergman27

OK. I have a theory about this odd TSB in which they announced intentions which, 4 years later, they never seem to have acted upon. I ran into this interesting UOA on the BITOG site for a 2007 Yaris factory fill at 1100 miles:

http://tinyurl.com/yjpnz4y

Note the 100C cSt value of 7.9

And then refer to this chart and table:

http://tinyurl.com/qqldw

This factory fill was clearly an Xw20 oil.

So my theory is that they want the EPA to test the car with Xw20 oil, to get slightly better numbers. But just doing a factory fill with that, without clearing Xw20 for use by owners is likely not kosher with EPA policies, so they had to OK it somewhere. But... they really would prefer that most warrantied cars use the 5w30 for superior protection. So... they OK'd 5w20 in the least conspicuous place possible, an obscure TSB, while leaving the 5w30 recommendation in the owners manuals and on the filler caps.

Sound reasonable?

-Steve

Sounds reasonable. I've always thought that lighter oils were more about what's good for mpg and less about what's good for the motor.