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I've subscribed to BITOG for years.

As usual with Forums, you need to hone your SEARCH skills, though, to find specific answers. Like, "Fuel dilution Lexus RX"

Moderate fuel dilution, just one more reason to support 5k oil changes. The only way to remedy dilution is an oil change. Your engine with thank you.

Yes, if you take the , together with the fact that the cars (oil pump programming etc) are designed for 0w-16, additives are really important together oil change frequency etc.

A positive side-effect of my having a PHEV with 50% - 70 % of odometer miles being fully EV is that I can get away with 10K miles oil change (since 10K odo miles <= 5K hybrid engine miles for my usage of my PHEV).

The Plug in hybrid does have the oil working less than in a regular hybrid.

There is a video below that states:

It Turns Out, Hybrids Are Really Hard On Engines

Hybrid vehicles are uniquely challenging due to the frequent engine start/stops, as well as lower overall engine temperatures, which can lead to water and fuel dilution. Sponsored by Mobil 1 – https://www.mobil.com/en/lubricants/ Hybrid vehicles are a great solution to improving fuel economy, but they have their own unique challenges. Because hybrid engines start & stop frequently, this often results in lower engine temperatures, which in turn can create issues with water and fuel dilution. Frequent start/stops, water, and fuel, can all create problems that exacerbate engine wear. To combat this, Mobil 1 has developed Mobil 1 hybrid, a full synthetic motor oil that is designed to meet the challenges that hybrid vehicles place on engines. This video will focus on three main subjects: how hybrids work, why hybrids are hard on engines, and what solutions exist to combat these challenges.

Given that Toyota Hybrids have gone hundreds of thousands of miles, their engineers have figured out how to deal with the above issues.

This video/"advise" seems a little less credible, because it was sponsored by Mobil1 (as credited in the video at the end), in an effort to sell their new "Hybrid oil" - which had motivated my question above). My question was about the basic premise of whether (1) the lower oil temperature is real in Hybrids (impossible to find from Youtuber types obviously) (2) causing more damage due to water condensation are actually correct to believe and to what extent (it may be real, but mathematically so insignificant - that the difference is academic).

And the Youtuber shares a hand-sketched plot that he then claims represents data from Mobil1 internally of engine temperature. If they had data, why not just directly share that data - instead of a hand-sketched graph ?

Most of the other Youtubers (including the Oil Geek) share measured data, which makes their points much more credible to me - aside of lack of "sponsorship" by any oil company.

Plus Mobil 1 only makes its hybrid oil in 0W20. The A25AFXS (2.5Lhybrid) requires 0W16. Amsoil and other companies make a hybrid 0W16.