I just crossed the 200k mile mark, and need at least another 100k out of this truck.

What's the best oil to use on our (very) high-mileage engines? I'm a highway warrior, doing 4000 miles per month. Would it be sane to change my filter once a month, change full-synthetic oil every two months, and coolant flush once per year (50k miles)?

200K is not even close to very high for a 4.0 Report back when you hit 500K Anyway, my personal preference in Toyota synthetic oil and filter and I change it every 5K miles. Since you do so much highway, 8K will likely be fine. I wouldn't push more than that though.

No, that would be dumb. 200k is NOT high mileage on Toyota engines.

I have over 280k on my 2003 V8 4runner and am just about at 330k on my 1999 Tacoma. The Tacoma had it's oil changed not too long ago with around 9k miles on that particular change. Engine runs like new still. The 4Runnaer I have barely had for a month but I have no worries about doing the same with it. It runs great. I run Toyota YZZD3 oil filters on both trucks and Shell Rotella T6 5W40 synthetic oil.

Have your oil tested at Blackstone Labs. They can tell you how the oil is doing and the general condition of the engine. They can test for the remaining additive and viscosity of the oil and recommend oil change intervals for you to get the most life out of the oil and the engine.

My opinion is that the oil doesn't matter anywhere near as much as not delaying oil changes. When I bought my T4R it was sludged up so badly from lack of maintenance that the oil light would flicker. That was a pain to deal with but all is well now, I monitor the pressure with a gauge.

We just sold my son’s, my old, 2005 Tacoma with the 4.0 and it had 355k miles. I changed the oil between 5,000 and 10,000 miles since new depending on how it was driven. Only reason for selling is I came across a nice 2005 sport V8 4Runner for him.

Driving those type of miles every month, I'd go with full synthetic and OEM oil filter every 8-10k. The 4.0 is just getting broken in at 200k!

I SWITCHED TO TOYOTA engine oil SN PLUS from mobil 1. toyota oil works better engine is quiet .. also a increase in MPG.
I do oil changes 7K miles of use but I do not use the runner on hywy use too much .. also I only run it 7K miles a year. 2016 model SR5.
I do the oil changes and I give it 45min for oil to drain.. no debris in the oil filter.. very hard to read the stick of oil level ,very clear oil .no oil drop on the 7K oil changes.

antifreeze you must use toyota coolant.. drain the entire system.. do the coolant changes around 100k miles of use ..

do the tranny fluid changes 120-130K miles .. drop pan do the pan/screen clean up ..

you do not need to use toyota oil, & its really no better than any quality brand synthetic. toyota doesnt make their own oils, last i heard it was a mobil product. also your 2016 doesnt have 200k miles like the OP's & he does 7k miles in 1.5 months.

& you do NOT need to use toyota coolant, many other brands offer the red coolant that is 100% rated for & compatible with toyotas. i use valvoline toyota rated coolant & so do countless others with zero negative effects. & its about half the price.

also most dont drop the pan on 4th gen 5 speeds & the majority of those who do say the filter is perfectly clean & the pan has very little debris even at 150k+ miles. doing a full fluid exchange at ~100k is a good idea, then just do some drain & fills every 50k or so. you can use whatever you want for oil/coolant, but dont tell others they "must" use a toyota branded product when its not true.

my advice for the OP's situation is to use a good synthetic oil like mobil or valvoline or any other common brand thats on sale & available at auto parts stores or walmart & use toyota brand filters. you can go 7-8k miles on the change & definitely dont need to change the filter every month, do it with the oil changes at ~8k. being you do mostly highway miles which are the easiest on the engine & oil, you should be fine doing 7-8k changes. & if you want proof/confirmation send in a sample for analysis as mentioned above. & 50k is too soon for this long life coolant, 100k should be fine.

It is high miles but has not worn down your engine if it has been maintained with regular oil changes. You could use a high mileage oil if you want...especially if you have any leaks. However, with mostly flattish highway miles, just change every 8K-10K. Highway miles are pretty easy on oil. You could even use an Extended Performance like Mobil 1 EP or Amsoil XL or Signature and go to 10-12 easy.

At 175K, I use Amsoil or Royal Purple HPS mainly but I'm happy to use whatever...even good non-synthetic or semi-syn like Pennzoil Gold. No leaks or problems. I do a lot of mountain highway driving so I change every 8K.

Wow, 4,000 miles per month? that's a lot. Congrats on 200!

I would say with all that highway driving you are a great candidate for extending your oil change interval. Highway driving is the easiest on engine oil, and the 4.0 is easy on oil to begin with.

Here is a used oil analysis, 7400 miles, 1500 of which was towing a 4500# trailer, and another 1800 miles of high altitude (5000-8000') high speed highway through CO, WY and MT. The rest was 1/2 and 1/2 40 mile mostly highway commute once a week and some 7 mile round trips to take the kids to school.

https://i.imgur.com/CN3a4Oy.jpg

I was using Amsoil's 5w-20 "lowest" oil - OE - and even that could have gone further; wear metals were low and there were plenty of additives left. I would bet with SS you could easily (and safely) go at least 2 months & 8,000 miles, probably 3 months and 12,000 and possibly 4 months and 16,000 miles. Of course use a UOA as mentioned by xtremewlr above to monitor your oil's condition.

But don't just take my word for it. I used to spend too much time on Bobistheoilguy.com and there were a few guys that went over 20,000 miles. Even though the site has turned caustic in the last couple of years you can still find good information there.

Totally agree with the earlier post about running longer with a synthetic oil. It doesn't have to be Amsoil; any quality off the shelf synthetic (even Supertech) will take you safely to 8,000 and perhaps beyond.

Lots of filter choices to go those distance as well. Extending will save you time and $.

Lastly - I practice what I preach, currently ~7,500 miles into a one year change interval with Amsoil and will post up the results after the change in late June.

I do not recommend your comments about using the improper fluids .

What improper fluids are you referring to? I read the comment and he doesn't say anything about using improper fluids.

what improper fluids would that be? are you suggesting valvoline zerex asian coolant can't be used in a 4th gen 4runner or that there is some damage it causes?

it is a fact that using a lubricant or coolant that is rated & compatible for use in your vehicle is 100% absolutely positively fine. millions have been doing it for decades in all brands of vehicles. im curious, do you have some proof or documentation to back up your statement?

coolants are variable on model years .. all have to look up the correct fluids..
THis is not the 1960's..

mixing the antifreeze with different chemicals in other antifreeze will cause problems..

I did the look up for my runner what coolant to use, have to use toyota antifreeze.

you have to use the correct fluids in your model year vehicle.. he commented on saying use fluids on the cheap ..

I do not dump my vehicles in 4 years then buy new. I keep my vehicles probably longer than his age LOL....

just throw anything in your ride on the cheap then buy a new ride next year..