Letting AI do the work

I don't know I guess it sounds reasonably reasonable but I've always had access to almost free oil at one point when I was a kid I never changed my oil I drove a car $400,000 mi just adding oil and changing filters every twice a year maybe seriously this was a Corolla a TE27 1.6 2 TC engine then a few years later I worked at a dealership and had an endless supply of oil and I had a Toyota Celica with the 22REC fuel injected engine I change that oil more than I changed my personal underwear which is everyday literally I was changing the oil in this silica about once a week just because I could not for any serious intense and purposes even that engine blew up and that car was barely used I was hoping that car might last me just because I liked it It was a baby super all the celica GTS. Did the same oil changing with 3S GE and GTE engines as some will remember that was the venable s series engine that was turbocharged in the all track rally car and what have you same thing with the beams engine which is the 3S engine with the better engine management system All of those engines were pretty much unabused and all kind of just destroyed themselves on their own not from lack of oil changes that's for sure and not by being driven by hooligans. So I'm not sure how all that would go course back in those days the oil wasn't what it is today so then there would be those things seems to be a real complicated bunch of malarkey kind of so I just don't get too serious with vehicles and mechanical things like this because they are just made for failure at some point that's the nature of these mechanical things you can try and make them lasted eternity but may not happen. I do know I was able to go through some 2Z FXRs or whatever these things are called 1.8 pretty quickly unlike a few of the other engines took a lot longer to get to that point

 

tl;dr

there are a lot of opinions here as to what causes the problem. they are all opinions.
maybe it is a combination, or maybe it was just poor design/engineering/testing

 

I'd argue that when they went up to the 1.8 liter engine they tried to squeeze too much engine into a small place and there's not enough gasket, as well as cooling between cylinders and then add in a poorly designed EGR system that raises engine temperature when it quickly clogs and you get a head gasket failure between cylinder #1 and #2.

As far as oil change intervals being extended, that's just a function of synthetic oil, but going too much longer between changing oil certainly would increase wear on moving parts, but not the head gasket. The high MPG piston rings that fail early in Gen3 could definitely be exacerbated by not changing the oil often enough.

Regardless, Toyota addressed the headgasket failure in Gen3 by simply moving the EGR system further down the exhaust system where temperatures are cooler and exhaust is less dirty so the system doesn't get clogged and it can do its job of reburning exhaust to keep engine temp lower, as well as create cleaner emissions.

Of course, despite this fix, @ChapmanF is still going to argue that the failing of Gen3 EGR can't be proven to be the primary cause of headgasket failure.

 

Yeah cool doesn't really matter it fails and that's that like it fails kind of like a clockwork thing All the Toyota engines I've ever owned in my life the head gasket was never a sacrificial part head gasket usually blew when you ran the HELL out of the car and ran low on water and and but those things all staying correct generally head gaskets were for the life of the engine some cases for me 400 and somehow a thousand miles no head gasket that I considered to be pretty normal all of the old Toyota engines would do that pretty regularly to t series A series S series . Those bread and butter engines didn't really have head gasket issues 22R truck and Toyota Celica not really head gasket eaters

 

So why does Gen3 Prius have so many problems with headgasket failure between cylinder #1 and #2?

 

Heck if I know but I would say if you're EGR is clogged and the EGR can't cool your internal combustion temperatures and they rise that would certainly put some excess heat on all the stuff that's in that tract the upper head head gasket top of the block tops of the Pistons for sure and there you go I guess the longest travel for those EGR gases is to get to one and two right It gets the three and four directly because they're well at that end of the motor right where the EGR is or the piping and hosing in the cooler one and two were you know another 14 in up the side of the engine

 

What messes up the EGR is carbon clogging.

Then the question becomes what causes the carbon in the exhaust. Is it only present in an engine with oil consumption?

My personal observation is no, carbon builds up in the EGR system without any oil consumption, at least none evident via drop in level showing on the dipstick.

Then there's the question: does oil burning increase the amount of carbon in the exhaust? Sounds plausible, and if the case then it would likely accelerate the carbon accumulation in the EGR system.

I wonder who coined the phrase "artifical intelligence" BTW, seems like a somewhat misguided rationale behind it?

Bottom line: if you don't have oil consumption, or very minor, I would not conflate that with the EGR system not accumulating carbon.

 

But EGR passages has been clogging up on engine since like the Chevy citation days and all that mess even before that you take the EGR off and there be a big black hole that's level to the top of the surface of the engine metal You couldn't drive a drill through it there was no getting it out sometimes you have to replace the motor that whole passageway would be full of that black stuff You could take all the tools you wanted and beat on it not much would happen to it You might get a few flakes here and there but that passion was dead No chemical you can put in it nothing melt the metal now I don't know if that was blowing head gaskets and other engines and all that back then but it certainly was stopping the flow of EGR gas quick fast in a hurry but I don't remember those engines having head gasket problems really they blew up but I don't think it was head gasket problems especially in engines like the 2.8 V6 they were just crappy motors but then again I've seen him go 250,000 mi with a bunch of guys from Saudi Arabia driving one My mother sold our Chevy citation to a family of saudi's after we had nothing but trouble with it for years they drove it for another 7 years without any problems kept it I used to see it around town all the time and talk to the guy He liked the car I couldn't stand the thing of course I wasn't even driving yet

 

It's not just carbon, but carbon and oil... hence the value of a oil catch can. I suspect putting EGR further downstream doesn't limit carbon exposure as much as it limits crankcase oil ventilation exposure? But I'm not clear on the plumbing that can produce so much oil in an oil catch can and if that plumbing could increase fouling of EGR because its not further downstream?

Maybe @ChapmanF knows?

 

Yeah but you've got to catch all that oil before it gets up into the path where it mixes and creates this carbon black or whatever it is You have to have a hammer and a chisel and even then it's slow going once that port is clogged up on normal engines General motors and the you know things like that 3SGE engines from Toyota to TC's regular stuff not the Prius FXRs this is nothing to do with that EGR is always been problematic If it gets clogged up you are fubar you won't be clean and squat I mean it'll be taking your block out and have it I don't know tanked and blasted and something or the head that passes where the EGR valve bolts right on to EGR valves usually like a cast iron thing and a lot of time does bolting to an aluminum head and that port there where the EGR gas would normally flow without all the business and coolers that the Prius has when that whole clogs on those type of engines yeah it's pretty down for the count sometimes you can get lucky and you can get enough where you can get a tool through there and get enough flow going again to where you can run it till it's over adding the cooler to me seems awfully weird I get it and all that but it just seems like that's going to create more of this carbon black oil may play some contribution to this business but all engines use a little bit of oil in the running process not gobs of it not where you can see it coming out the tailpiper causing serious damage but they just do I mean a good running engine you won't see it on the stick in an oil change but that's neither here nor there it seems like.

 

Precious little oil makes it through the combustion chamber, I’d wager.

 

like i said, a lot of opinions...

 

That's generally the idea although some engines have had trouble with that process.