The need to change the fluid is an obvious bone of contention, but what seems to be universally accepted by those in the know’, is that you should NOT flush these transmissions. There also seems to be agreement, even amongst the periodical oil change advocates (eg. car care nut), that if an oil change has not been carried out on an older transmission (e.g. +100k miles) then a lot more harm than good will come from an oil change.
With my 39k mile August 2017 GSF, I’ve been procrastinating ‘trust Toyota and leave well alone’ vs ‘listen to the YouTube/social media experts’ and distrust Toyota’.
I was leaning heavily in favour of the latter, but now question the notion that Toyota state ‘lifetime’ as a sales tactic. Thinking about it, I very much doubt whether a gear oil change at 6 years/60k miles would influence anyone in their choice of car at all. Furthermore, gearbox failure/malfunction even after 10 or 15 years (or any age for that matter) would not enhance the reputation of a manufacturer. Lexus, more than most, seem to place very high value on their products being reputedly bulletproof, so I am not totally convinced there is any real incentive for them to claim ‘for life’ if that is not the case. That would also not align with them sticking to annual/10k mile oil/filter changes when other manufacturers went down the 2 year road which is probably a lot more of a sales attraction.
Im also considering the fact that ‘inspection’ of the transmission oil is in fact a scheduled service requirement. What exactly the inspection involves I don’t know, but if it includes evaluating the condition as well as a level check, then this would mitigate any potential for unanticipated oil degradation, as presumably an oil change would need to be carried out if the condition is found to be sub standard. This principle has been applied for many years in industries such as rail. The huge diesel engines in locomotives (which can hold a couple of hundred gallons of lube oil) have oil changes based on chemical analysis rather than periodicity. In the case of a car that holds a small amount of engine oil, the cost of analysis isn’t worth doing when it can be changed relatively cheaply/easily.
The procedure for F car transmission oil change is pretty complex, and given the much longer anticipated life of the oil, then an analysis in whatever form that may be (perhaps even just visual), could well be more appropriate.
There is also the consideration of the possibility of a transmission oil change not being carried out correctly, i.e. level checks at precisely the correct temperature. Even Lexus technicians are unlikely to have much experience in doing this. For me the ‘leave well alone’ and ‘if it ain’t broke don’t fix it’ principles are starting to look pretty compelling in this case.
In conclusion, I’m leaning towards trusting Toyota…but then again there is always that nagging doubt! 😩🤣