What's so dreaded about the GPF? Genuine question.
I'd guess it's the same as DPFs in diesels. It collects all the nasties that some folk don't want releasing into the atmosphere, then every so often when it's stored up enough, it goes through a process that releases all those collected nasties into the atmosphere.
It converts those nasties (carbon particulates that can get lodged in your lungs and cause all kinds of health issues) to carbon dioxide. I'd rather have the low level carbon dioxide than the particulates in my lungs.
So do you need to go on a long run every so often to get the filter hot enough to do this?
I did relatively few long motorway journeys in my bmw 335d and had problems with the dpf blocking. Any such problems with petrol filters?
Petrol is less efficient than diesel because it creates more heat and less kinetic energy in combustion (diesel is only 8% more energy dense yet is 30-50% better in mpg overall).
Diesel combusts at a higher temp but chucks less heat into the exhaust. As a result, GPFs heat up quicker than DPFs.
However, you don't just need heat to convert soot (carbon) to carbon dioxide, you need oxygen from air - and therein lies the problem for GPFs. Diesel engines run a big excess of air, petrols take in just enough air for the oxygen required to combust the fuel (and nothing more). So when you're driving along with your foot on the accelerator, after 4 or 5 miles you've got a hot GPF but no oxygen...
Unless you drive on a certain way.
If you're one of those people that is always on the accelerator pedal and then on the brake, you'll only get forced regens with the car forcing more air tgrough than it should need. When this happens, your mpg will plummet (way more than a diesel does under forced regen) - you'll get about 60% of your normal mpg when a GPF is doing a forced regen.
If you're one of these people who reads the road ahead well and comes right off the accelerator when approaching a slower car ahead, or a roundabout/junction, you'll regenerate passively. The only time the petrol engine pulls through an excess of air through normal operation is when you're completely off the accelerator while moving and the engine has no fuel going in. This doesn't work when coasting or idling at a stop because there's still fuel going in.
My wife is one of those who is always on thd accelerator or the brake and wonders why her Polo GTI+ is doing 20mpg and not 32mpg on her 6 mile trip to work once every 2k miles.
