2015 Toyota Highlander AWD 3.5 V6 Maintenance

Going in for regular oil change at 75,000 miles. Dealer recommends changing differential and transfer case oil now, and wait for auto transmission fluid at 100k miles. None of these have yet been done. Obviously the maintenance guide says ‘never’ on the trans fluid (sealed unit etc), unless Special Operating Conditions (towing, car top carrier, heavy loading), then it’s every 60k miles. Differential and transfer case oil is also never unless special conditions, then it’s every 15k miles.

Car is driven under normal load conditions, no towing. Severe winters - Chicago area.

I know a little about trans fluid and the debate on that. I know nothing about diff or transfer case fluid changes. Thoughts on the dealer schedule vs Toyota, and doing the work now? Any unforeseen problems?

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Toyota is the authority. The dealer is not. Too many whack opinions from dealers for me to grant them authority.

Which do you think is cheaper?

Replacing a differential/transfer case? Or replacing the fluids?



I just need a competent opinion, not smug snark, thanks. I am well aware that fluids are cheaper than the parts, but my limited knowledge of cars doesn’t tell me if it’s a good idea to do these things now, with 75k miles after not having had them done, ever. And, who is right, dealer or Toyota?

Do the diffs, the transfer case fluid and the trans fluid NOW. If can’t hurt, it isn’t nearly as expensive as replacing any of those components. I tend to OVER maintain based on my owners manual recommendations. A little OCD, sure, but my 137K mile transmission looks as clean as new in the pan. Same for my diffs. Every 15K sounds like a misprint for diff and transfer case oil. Too short even for me.

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Yeah, I was surprised at the 15k miles. Especially as normal conditions is ‘never change’. I guess if the car tows often? I think I’m going to order the diff and transfer case fluid change, and press them on the trans fluid as to why they recommend 100k miles only, and not 60k like the diff/transfer case. This is what I hate about car maintenance, go to 100 places, get 100 different schedules and opinions. Sometimes differing opinions at the same bloody place.

Well, you will get a bunch here, too. Opinions are like, well, you know, and none of thinks ours stinks! You will see opinions from Owners Manual Severe Service recommendations to 30K trans fluid changes. Generally, all will say never go over the recommended miles.

I do my own work and the recycling center is close so fluid changes don’t bother me much from a time or cost perspective. I did pay for my last ATF change in my truck because it is very messy. Still worth doing.

Well thanks for your opinion! I am very interested in the trans fluid change debate. I’ve read quite a bit, and it will be interesting to see if these ‘lifetime’ fluid transmissions last the legendary length of time (300k and over), like Toyotas of old, bearing in mind how most people (don’t) look after their cars. I was also reading about the Mobil 1 20,000 mile oil change. That seems a stretch and a half, even for me, someone who tends to believe the synthetic hype.

The possibility of a fluid change being done incorrectly, say, with the wrong fluid, is one reason some carmakers have recommended against it. The chance of damage due faulty maintenance is greater than the chance of damage due to no maintenance, say.



Yes, I read that one of the reasons they took away the trans dipstick was to stop people from incorrectly believing that the level was too low, and then adding too much fluid, thereby damaging the unit. Not sure whether to believe that or not. I’m thinking auto companies don’t care what consumers do to their cars, especially if it means more repairs.

I’m gravitating towards the idea that it doesn’t matter all that much if you do or don’t change the trans fluid very regularly because it’s way more effective and long lasting than it used to be, but changing the fluid at regular (smallish) intervals might give you an extra 50 to 100k miles before something else kills it, dependent on the quality of the transmission etc and hoping the engine or other major component(s) didn’t fail in the meantime. There’s no definitive study of course, so it’s hard to tell whether your very regular fluid changes actually did anything.

My main reason for hesitation is that I do not want to mess anything up by changing the fluids. Because you hear that story a lot, too…

@Tester Thanks for the link.

I would change all those fluids now, you’re at a reasonable miles for them. Toyota has some odd ‘severe service’ recommendations. I stopped going to my Lexus dealer service department when they insisted I change the transmission fluid every 15k (that was the severe interval) on my ES300. They claimed they wouldn’t ‘stamp’ my warranty book unless I did it. I found a good independent, never went back to the dealer.

Wow, every 15k miles for trans fluid. That’s insane. My Highlander lists 60k for special conditions. I think that dealer was on the make. They usually markup the invoice through ‘carbon flushing’ and other nonsense, which I was recommended for at about 15k miles. I changed dealer. I’d go to Acme quickie lube, but I trust them less than I do the dealer with my cars.

Strange that the dealer recommends differential and transfer case oil changed now and to wait on the trans fluid. I’d rather change the trans fluid now, and change those other fluids later. Or now. But trans fluid generally needs changed more often than differential oil, in my opinion.

We have a 2013 Highlander. I did a drain and fill on the trans at 100k miles. So far, so good. I probably should have changed it sooner, but at least I did it and disregarded the “sealed for life” statement in the manual and on the dipstick. I’ll probably drain and fill again at around 130k or so.


Hey John, Yes it is odd regarding the timings. I’m going to press them on it when I go in next week. What did your trans fluid look like when you changed it at 100k? Did you do a full drain or just what drained out when you removed the plug? I really like this car and would like to keep it for as long as possible!

The fluid was still red, smelled ok and didn’t seem burnt at all. I just pulled the plug, measured what came out, and then added that amount back. I asked the local dealer about a trans service including replacing the filter and they looked at me like I was crazy. “Sealed for life”, and all. I think a full flush and a filter change would probably be more ideal. I plan to change the fluid (by pulling the plug) in shorter intervals now (30k or so). Kind of an extended flush. I haven’t decided about changing the filter, although I think it would be a good idea. My wife won’t stop driving it long enough for me to drop the pan! :grimacing:

Be sure to have the correct crush washer on hand if you decide to pull the plug and refill. I found that out the hard way. Most of my previous vehicles were domestics, and my only other experience with crush washers is the copper washers on brake line fittings. I didn’t realize the drain plug on the trans needed a new washer until after the fact when the plug seeped a bit of fluid.

OK , then just change the fluids . Forget the 20000 mile advertisements for Synthetic oil , lifetime transmission fluid and other things . Of course this can be done by an independent shop . Same goes for hoses and belts it never hurts to change then before it is too late.

That’s what I hate about the Toyota dealerships . . .

The counter guys are so smug when it comes to their “life time” fluids and filters

They often say “Nobody has EVER asked for transmission fluids and a filter” . . .

Sell me the parts

Spare me the attitudes

Thank you very much :smile_cat:

You ever “dress” a crush washer with the appropriate stone . . . ?

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Interestingly the Toyota dealer didn’t push the ‘sealed for life’ thing. He said they recommend changing the ATF at 100k miles. I don’t know if this is because it’s a potential towing vehicle though. Maybe the answer would be different on a sedan.

There’s no way I’ll be doing it myself. I’d be paranoid I screwed something up. And with me doing it, it’s quite likely. Plus, just as there are several opinions about whether and when to do it, there also appear to be several different methods too. Some say you have to rig it up to a scan reader to get the correct temp. Others just take the plug out and drain. Others yet say you have to do it two or three times at 100 mile intervals to get it all out. Bah. Cars are way too complicated! But, they’re generally more reliable than they used to be I guess.