Rislone 4720 to keep EGR system clean?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by DJLand, Jun 21, 2026 at 2:42 PM.

  1. DJLand

    DJLand Junior Member

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    Hi. I'm a high-KM Gen 2 owner, very satisfied. Spouse would like a newer Prii, preferably a V, but having read earlier here about the probability of EGR/Head gasket problems I was sour on used Gen 3s, mostly now with 150k kms or more. Researching more here and on youtube I think I can handle the cleaning project and am actively looking for a lower KM V.

    Yesterday I met a fellow with a V. He said he had run a Gen II Prius for 575,000 miles and then got his V, which now had 375,000 miles. He drives to from Florida from Ontario and sometimes drives for Uber there. He said he has been putting the Rislone product in regularly (maybe monthly?) and has not had any EGR problems. Sounded a lot easier than the mechanical cleaning if it works. Has anyone on here tried this? It seems like easy way to avoid having to tear the whole intake system apart every 100k km.

    I have read also that the EGR problem is exacerbated by a use pattern of mostly short trips where the engine doesn't run at cruise temperature often enough. This would not be a problem for us as we frequently drive 200+km to our cottage and back and annually have been driving to southern Mexico, 5000 km each way, obviously running at cruising temperature for 50 hours each way over a week or so.

    I guess an experiment could be done by tearing down enough to see and document the EGR pipe state of carbon build-up, running a tank of gas with the Rislone 4720, then looking back in the EGR pipe to see if there was any effect.

    Thanks for any observations.
     
  2. PriusCamper

    PriusCamper Senior Member

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    Pour and Pray rarely works but seems as though people use this to turn off a P0420 to pass inspection... Not sure how it does that, but I'd rather go with cleaning and inspecting and an oil catch can instead of this. But if you were to try this for keeping the EGR cleaner I suspect the amount of material in oil catch can would be less, which would prove that it works... Doing direct inspection of EGR would be a more long term and harder effort than just checking what's in an oil catch can.
     
  3. CR94

    CR94 Senior Member

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    Yeah, IF.
    Why or how would that stuff have any effect on the EGR system?
     
    #3 CR94, Jun 21, 2026 at 9:30 PM
    Last edited: Jun 21, 2026 at 10:01 PM
    Brian1954 likes this.
  4. frodoz737

    frodoz737 Top Wrench

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