For your 2007 Buick Lacrosse, I’d stick with Dexron VI equivalent ATF. You can sneak some more miles out of the 4T65E
before it starts to do things. I hope you replace the tranny filter and clean off the oil pan magnet too.
For some 4T65E problems, thinner ATF helps with slow or jarring 1-2 shifts. Thicker ATF may help shudder problems.
Of course fixing the root cause is best when it happens.
I’d plan to grab about 6 - 8 long thin neodymium bar magnets to beef up the usually weak GM magnet in the oil pan.
Google “4T65E magnet” GM put out a TSB since they used cheap weak magnets for many years. 2007 is iffy, could have
the extra cheap on in there. Even their ‘good’ ring magnet is not enough.
In my case, I put several bar magnets near the OEM magnet position and then 4 on the metal plate of the filter
next to the intake. I used a compass to orient each so they were all “in phase” making the metal plate of the
filter a good south pole. The rest of the oil pan is virtually “zero clearance”. Meaning there’s no room for
anything else on the pan except in very specific locations.
Why did I do this? GM admits their magnet is not strong enough to catch all the wear metals (from gears, etc)
and the metal particles gravitate to the PCS solenoid and shift solenoids causing shift problems. Of course
they had to know that when they gambled on going cheap!
See the Pics on Page 1 of the PDF for the GM location for their ‘stronger’ magnet:“ MAGNETIC FILTER ADD ONS – DO THEY WORK? “ https://app.box.com/s/31t6azxju7ncllw5seda