Preemptive EGR Valve and Intake Manifold Replacement?

welcome!

1) it is thought to be a strong possibility

2) yes, or they can be cleaned, see @NutzAboutBolts youtube video

3) stick with the oil change interval, good idea. think about adding an oil catch can

4) change the tranny fluid

5) all the best!

 

Note that your Prius also has an EGR cooler, and it is susceptible to clogging. If you do any EGR work, cleaning that cooler (replacement is expensive) is one of the essential steps.

Whether or not EGR is actually linked to head gasket failure, is another debate.

 

They are expensive parts to replace, and I haven't heard of much going wrong with them* that isn't solved by cleaning, so I think even if there were an issue, cleaning is the way I would lean.

A sort of hybrid option is to pick up a previously-loved cooler and clean it first, then swap, so the car isn't down for the time it takes to clean the original cooler.

The car has self-test results you can easily check to see how far along the clogging spectrum it is, and (if you pull up the result at regular intervals), at what rate it is progressing.

The small individual passages in the intake manifold are probably worth just visually checking and cleaning from time to time. That's an easy job, and those passages aren't covered by the self-test you can ask the computer for, so you're otherwise blind about those without taking the manifold off to have a look.

If you do clean or swap, the test results page linked above benefits if you add to it what your results were before and after the cleaning or swap, and your mileage.


* the one exception I remember was in ozmatt's car, where in a hard hot uphill drive on a 40 ℃ day, the EGR valve got hot enough for an internal part to melt. That was fixable by using a hot knife to make it the right shape again. You will probably not see such an issue unless driving in similar insanely hot circumstances.