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Hagerty Employee

Piston Slap: Diesel soot drama, except with modern gasoline engines? | Hagerty Media

Arnie writes: I don't understand why gasoline cars in Europe need a particulate filter. I understand diesels generate a lot of particulates. I have never previously heard of of concerns with gasoline particulates. Will these filters eventually be required in the U.S.? Sajeev answers: This is a great question as it was an eye-opener for [...]
Intermediate Driver

I say go back to PFI. I sold a '13 Jaguar XKR over this issue. The soot gets in the oil as well as the air. In the oil, it can cause timing chain tensioners to stick and you can imagine where that leads. I didn't need a 10 or 15k engine rebuild. Is that particular issue solved? You won't find an answer. They are even formulating the new synthetic oils to keep the soot in suspension. Good luck with that. There is also the problem of coking up valve stems, to the point they can't be cleaned. Folks having to have the heads removed to replace valves. Some manufacturers are adding PFI back to the intake to try to clean the valves. What does that tell you? And my major question, are these cars going to last 100, 200, 300,000 miles without major service or engine rebuilds? I'm not one who can buy a new car every 3 years and think many are in that same boat.
So, for me, I'm sticking to PFI. And won't go past the 2009 vintage of my chosen automotive poison.
Intermediate Driver

"...contributing to respiratory and cardiovascular illnesses and even premature death especially among the vulnerable: children, the elderly and those with respiratory conditions.”
It's COVID all over again! RUN!

I went against your advice and looked up Stevens-Johnson Syndrome but I didn't go looking for images - I'll trust you at least on that. It sounds rather unpleasant, to say the least, and I certainly hope you are recovering/recovered. It says that as few as 20,000 people will get it per year, which as we've also learned from some cars in the past, rare does not always mean valuable.

And for what it's worth, PFAS will probably kill us all before the GDI particulates will. Hope that Scotchguard you opted for in that 1988 Dodge Aries was worth it!
Community Manager

Thanks @Land_Ark I am 99% recovered, and I just need to avoid certain drugs going forward. Provided I don't take the wrong thing for an ailment, the condition just makes me more interesting to the medical staff of any organization. Not a great thing, but not a bad one I guess. 


It totally changed my life, and it makes me want to avoid health problems for others. That's in general, and in this case, maybe Toyota's Hybrid (sorry) PFI/GDI setup is the way to go? 


My BMW 335i, with direct injection, went over 200,000 miles, and was running strong when i sold it.

One of the services BMWs like these need occasionally is walnut shell blasting of the intake valves. Carbon can build up on the valve stems and restrict airflow. In 200,000 miles, my car had that done twice. BMW strongly advises the use of only tier 1 gasoline to reduce this problem. Both times BMW paid for it. I'm told that new versions of that engine don't need this service as often, which, in practice, probably means never.

I think the worst part of the soot issue is the unsightliness of he chrome tailpipes after a while.
Community Manager

You are probably right, but who knows what GDI soot does in the next 20-30 years. Hopefully nothing significant. 


I love the unintended consequences! 🙂 While I'm not a fan of soot: I'm entertained by the idea of the latest technology ( well not really a new technology; Ford was doing this with their stratified charge engines back in the 70's; others were doing direct injection further back) causing more problems than older tech. I'm also a bit entertained by the adherence to CO2 being evil. 🙂 If only all the flora on Earth were aware that their food is causing the Earth harm, maybe they would just die off and save the Earth for everyone else! 🙂 As this is dug into a bit deeper you will find that the quality of fuel matters a great deal also. Certain fuels, with certain additive packages, will cause more soot in GDI engines.
Makes me a bit nostalgic for the days of Bruce Crower's High Mileage Engine systems from the 70's.
Pit Crew

Can someone explain why DI engines have more soot or particulate? I thought DI engines were supposed to burn fuel more efficiently? When wood burns in its most efficient state, it produces the least amount of soot.
Community Manager

From what I have read, most of the issue with soot is from the result of incomplete combustion from DI engines. Fuel and air doesn't mix as well in DI engines, as they don't have the time to mix like PFI systems that atomize fuel in the intake manifold. 


I do notice a poof of soot and a distinct burning smell when someone in a newer car gets on the gas. They are all DI vehicles. Toyota/Lexus went with port and direct injection on their V6 motors like my IS 350. Here is a good article on this...