"Big rigs will have to slash fuel consumption by 23 percent".

[Hersbird]

I can't believe a simple internet search cannot find what the class 8 fleet average fuel economy is but I think I found something buried under a different North American Council For Freight Efficiency report. They show the fleet average being pretty consistent from 2012 to 2018 the data they report. In 2012 it was 6.0 mpg, then it actually went down for the next few years to 5.8 (probably increased emission requirements) then it creeped back up to 6.0 mpg. I don't see any info newer than 2018 but certainly there is no 33% improvement in the last 10 years.
https://nacfe.org/annual-fleet-fuel-studies/#

[oil pan 4]

The new ones were supposed to get around 8 mpg then dpf hit big trucks.

[Isaac Zachary]

Originally Posted by oil pan 4

The new ones were supposed to get around 8 mpg then dpf hit big trucks.

I've understood the DPF doesn't have a huge effect on fuel consumption on most big rigs unless not maintained properly. The thing is that if used for long distance driving it incinerates it's contents without the need for active afterburning. But for short routes, yes, it needs to regenerate by adding fuel.

Tip for all you newer diesel owners. Wrap up your exhausts with heat tape. Diesels don't have as high exhaust temps as a gasoline engine does so wrapping exhaust post turbo won't hurt anything while also keeping catalytic converters and DPF's hotter so you end up needing less fuel to regen and you also keep things less clogged with suet.

[JSH]

Originally Posted by Hersbird

But that may be just picking a terrible 2006 model that was finally fixed.

How much better is the best available class 8 2021 compared to the best available 2006? Or the average 2006 to 2021? Or the fleet average 2006 to fleet average 2021? That was a long report giving numbers that really have no bearing on the problem and probably took longer to dig out, than just telling us the non conformational bias numbers.

The Cascadia is Freightliner's most fuel efficient Class 8 on-highway truck and it was a new model in 2007. (I had a typo in my last post)

The Cascadia Evolution came out in 2014 and was 7% better than a EPA10 Cascadia. It clocked in at 9.3 mpg running cross country at 76,000 lbs.

https://www.bulktransporter.com/flee...red-by-detroit

The Cascadia was updated in 2017 and the New Cascadia (yes that was the official name) with the new Aero X package beat the Evolution by 8% running from Detroit to Portland head to head

https://www.truckinginfo.com/156905/...a-fuel-economy

Originally Posted by Hersbird

I can't believe a simple internet search cannot find what the class 8 fleet average fuel economy is but I think I found something buried under a different North American Council For Freight Efficiency report. They show the fleet average being pretty consistent from 2012 to 2018 the data they report. In 2012 it was 6.0 mpg, then it actually went down for the next few years to 5.8 (probably increased emission requirements) then it creeped back up to 6.0 mpg. I don't see any info newer than 2018 but certainly there is no 33% improvement in the last 10 years.
https://nacfe.org/annual-fleet-fuel-studies/#

The last major HD emissions requirement was in 2010. 2004 was EGR, 2007 added DPF, 2010 added Urea injection. There were smaller changes in 2013 and 2017. The next big one is 2024 when CARB wants a 75% reduction in NOx.


No the fleet average isn't up 33% in the past 10 years. You can make fuel efficient trucks but you can't make fleet buy them or drivers run at optimal speeds for fuel economy. (It is amazing what percentage of truck fleets are still running 15W-40 oil)

According to this article fleet economy is up 15% from 2009 to 2018 despite fleets running higher speeds

https://www.ttnews.com/articles/nacf...y-15-2009-2018

Originally Posted by Isaac Zachary

I've understood the DPF doesn't have a huge effect on fuel consumption on most big rigs unless not maintained properly. The thing is that if used for long distance driving it incinerates it's contents without the need for active afterburning. But for short routes, yes, it needs to regenerate by adding fuel.

The biggest issue for DPFs when they were new was idling. The worst thing you can do for a diesel with a DPF is idle a lot but drivers will still idling their trucks overnight for "Hotel Loads". That killed a lot of DPFs. (Running the wrong oil will kill a DPF too) Now fleet are running trucks with APUs (Auxiliary Power Units) that burn a quarter of the diesel fuel compared to idling the main engine and provide heat, A/C, and power.

[oil pan 4]

Originally Posted by Isaac Zachary

I've understood the DPF doesn't have a huge effect on fuel consumption on most big rigs unless not maintained properly. The thing is that if used for long distance driving it incinerates it's contents without the need for active afterburning. But for short routes, yes, it needs to regenerate by adding fuel.

Tip for all you newer diesel owners. Wrap up your exhausts with heat tape. Diesels don't have as high exhaust temps as a gasoline engine does so wrapping exhaust post turbo won't hurt anything while also keeping catalytic converters and DPF's hotter so you end up needing less fuel to regen and you also keep things less clogged with suet.

The dpf regeneration burns fuel. Ford specifically says in their early dpf trucks that regeneration cycle can burn 17L of diesel fuel. What a waste.

[Piotrsko]

17 or 1.7? Our pig pee using school bus quoted .2 gallon per cycle and the bloody thing regenned EVERY trip to AND fro.

[oil pan 4]

Seventeen. They likely don't use anywhere near 17L every regeneration cycle.
The early first generation of DPFs just need to be deleted.

[Isaac Zachary]

Active regen uses fuel. I'm not sure how much. There is either from an injector in the exhaust system or the injectors in the engine itself spray fuel during the exhaust cycle. This is to elevate the temperatures of the DPF and incinerate most of the particulate matter.

Passive regen doesn't spray fuel into the exhaust. It relies on long trips that heat the DPF enough with just plain old exhaust.

This is another reason why ICE's still makes more sense for long distance trips and electric for short ones.

[Piotrsko]

After the debacle with an injector in the exhaust system recall, VW delays the heavy injection to after tdc leaving extra rich burning fuel exiting the cylinder. Does booger up the EGR with soot, heats up the coolant. Valves? Turbo? I dunno, but the stupid system still regens on long trips about every 50 miles.

There's a silent recall out for TDI's to have the egr system fully replaced after 70k miles on cars that set a check light.

[JSH]

Originally Posted by oil pan 4

Seventeen. They likely don't use anywhere near 17L every regeneration cycle.
The early first generation of DPFs just need to be deleted.

Which Ford diesel uses 17L of diesel to regen? I'm shopping diesels at the moment and can't find anything on this.

(I'm assuming this is for a forced regen where a truck has been run in stop and go and idled so much that the engine has derated or dropped into limp mode.)