Hi All,

I'm thinking of moving to synthetic for my 2003 Yukon XL, with about 57k on it.

I don't have the parts and I don't think I'll be able to do the "manual flush" like this, and I'm wondering if it would be a problem to just put in Amsoil ATF, or some other synthetic ATF. Drop the pan, drain the fluid, change the filter, then refill with Amsoil. I understand this is going to leave about 50% of the old fluid in the vehicle, so I'll now have 50% convention and 50% synthetic.

I'll likely drop the pan and drain again in short order, perhaps 6 months or 10,000 miles, whichever comes first, and then again 6 months later or 10,000 more miles. I figure that way I'll get most of the conventional ATF out and have it replaced with synthetic.

I've searched and read a ton on transmission fluid changes, and it seems that the general consensus on mixing synthetic and conventional ATF is that it's ok, it's just that you won't get the full benefit of synthetic ATF as long as you've got it mixed with conventional. After three changes, I should be to 87.5% synthetic, if dropping the pan will drain out 50% of the fluid.

I thought I'd ask here, one last time, to see if the conclusion I've drawn (mixing is ok) from my own reading is in error. Let me know your thoughts. Thanks!

-Josh