If price was not a consideration, Gas or Diesel?

otrfun wrote:
rather than downshift when zero throttle is insufficient, it can then selectively apply reverse thrust or throttle (for lack of a better word) with the exhaust brake rather than downshift like a gas engine.

You're going to have to explain that one.

DWeikert wrote:

pnichols wrote:
However, since the exhaust braking engine back pressure mechanism is different than the gear braking engine back pressure mechanism ... maybe exhaust braking can somehow feel different to the driver. :h

The big difference is a gas engine just doesn't have the compression to slow down the vehicle like a diesel does. The transmission on a gas engine will take you into the high RPM's trying to compensate and still not do as good a job slowing the vehicle as the diesel at much lower RPM's.

Both a gas and diesel engine can downshift and use the engine for braking purposes. However, the gas engine is limited to only zero (and varying amounts of) throttle to vary engine braking. Once zero throttle is insufficient for braking, it's then left with downshifting forcing the engine into a high RPM state to increase braking. A diesel (with an exhaust brake) on the other hand, can also use zero (and varying amounts of) throttle to vary engine braking. But, rather than downshift when zero throttle is insufficient, it can then selectively apply reverse thrust or throttle (for lack of a better word) with the exhaust brake rather than downshift like a gas engine. This is a huge difference in engine braking capability (vs. gas) that must be experienced to truly appreciate. You can also place a diesel exhaust brake in manual, non-auto mode and use it full-time while driving in normal traffic. In this mode it activates everytime you take your foot off the throttle. In some types of traffic it can save untold amounts of wear and tear on your brakes. FWIW, on my '16 Cummins there is a dash display that shows the amount of exhaust brake in HP. Depending on conditions it can vary from approx. 70 to almost 200 HP. I might also add the sound of all this stuff going on under the hood can be quite entertaining on a long, boring drive in the mountains--lol!

kohldad wrote:

Something must be very wrong with that 2016 diesel.

Huge difference between your 2005 5.9 and the newer 6.7 because of the emissions. He also hauls a 15k FW and his 04.5 5.9 averaged 3-4 mpg better hauling the same FW. The 6.7 does pull it a lot better, but uses more fuel to do it.

No, not that huge of a difference. Have an 07. Had a fleet of 2014s. Mileage not that different. But a lot of people like to see what they want to see when justifying their purchase.

Not dissing the Hemi here, but if you average 12 mpg with even your lightweight TC on it, you're not doing the calc right or you're hyper miling it. If 12mpg is even possible doing that.
If you loaded that same TC on a srw new diesel and drove it identically as the 12mpg gas run, you would get more than 12 mpg. You would get more than 13 or 14 too.
I love fuel mileage claims... I've put a million miles or so on my gas work trucks and personal trucks and another few hundred thousand on diesels. Along with being responsible for fleets of trucks as well as the drivers expenses. When talking HD gas pickups, 12-13mpg empty or with toolboxes is the norm. I've never seen double digit gas mileage once anything bigger than maybe a 6x10 util trailer is hooked up.
Of course, when one has a company credit card and a job to do, fuel mileage concerns are at the bottom of the list, but it's all relative.

pnichols wrote:

otrfun wrote:

pnichols wrote:

otrfun wrote:
Can I politely assume you haven't driven a Cummins with the cruise on, the exhaust brake (EB) set to auto, while driving up and down 5-7% grades with, say 13,000 lbs. behind you . . . with your feet relaxed on the floorboard? ... snip

I've never owned a diesel ... but I have driven our 12,000 lb. RV up and down 5-7% grades while leaving the cruise set on and yes, the transmission does automatically downshift to whatever gear is necessary to maintain whatever speed I have set the cruise at. If I'm not in cruise, then subsequent brake taps bring the gearing down to whatever I need or want on downgrades.

However as I mentioned earlier my rear differential is a 4:56, so that helps tremendously with hold-back from 5th gear on down.

I've driven a number of gas vehicles that auto-downshift for braking as you describe. If you were to personally drive those same grades with any of the late model Big 3 diesels (cruise on, auto EB activated) I believe you would better appreciate how different true engine braking is vs. simple downshifting.

Hmmm .... I'm tempted to say that "downhill holdback" is "downhill holdback" .... with respect to diesel exhaust braking versus gas gear braking whenever a given weight vehicle combination is able to be slowed enough or too much.

However, since the exhaust braking engine back pressure mechanism is different than the gear braking engine back pressure mechanism ... maybe exhaust braking can somehow feel different to the driver. :h

Hmmm, I'm tempted to say you have no idea what you're talking about....

pnichols wrote:

However, since the exhaust braking engine back pressure mechanism is different than the gear braking engine back pressure mechanism ... maybe exhaust braking can somehow feel different to the driver. :h

The big difference is a gas engine just doesn't have the compression to slow down the vehicle like a diesel does. The transmission on a gas engine will take you into the high RPM's trying to compensate and still not do as good a job slowing the vehicle as the diesel at much lower RPM's.

I see a lot of posts from people that never owned a diesel claiming a gas engine is just as good. Sigh...

For my $0.02, if I have any kind of a load, it'll be a diesel. I hear lots of whining about pollution controls hurting fuel mileage. That may be but my Duramax has the DPF and with my camper on the back I still average 13-14 mpg highway. The Duramax doesn't have a true exhaust brake but they emulate it with the variable vanes in the turbo. Going down the steepest grades in the Rockies I still occasionally have to push down on the skinny pedal because the engine is slowing me down too much. Meanwhile, similar trips in a gas truck would have me both worrying about a piston flying through the hood due to the high RPMs and still having to ride the brake, hoping they aren't overheating.

To be honest, with my tiny camper, the Duramax is overkill. But as Colonel John "Hannibal" Smith says, overkill is underrated. I'll gladly pay more for for the diesel then enjoy the relaxed drive the entire time I own the truck.

In my case I went from a 97 5.8L GAS to a 2017 6.7L PSD.

While shopping I wanted a long bed and "super cab" rather than regular or crew. As it ends up the truck I took home was the only "super cab" on the lot and just happened to be a 6.7L PSD.

I'll have to admit that I was not exactly shopping for a diesel at the time, just a new modern truck. The 6.2L Gas might of been a good fit but like I mentioned, the PSD was the only one on the lot (I had visited LOTS of lots which had TONS of crew cab PU's but no super cabs).

The test drive was an eye opening experience.

With the low mileage that I put on the truck it will likely outlast me. Given the choice of GAS vs DIESEL after experiencing a modern Diesel truck I could never go back to gas. The driving difference between my old gas truck and the PSD is/was Night and Day. Totally different experience all together.

- Mark0.

Something must be very wrong with that 2016 diesel.

Huge difference between your 2005 5.9 and the newer 6.7 because of the emissions. He also hauls a 15k FW and his 04.5 5.9 averaged 3-4 mpg better hauling the same FW. The 6.7 does pull it a lot better, but uses more fuel to do it.

We don't know what speeds we compare?
11 mpg on diesel driven with camper at 70 mph sounds pretty reasonable, 14 mpg on gaser at the same speed & load does not.

I actually have my father's 2016 diesel this weekend with a 5k TC on the back while I'm use to driving a 2015 6.4 Hemi with a 2.5k TC on the back, both with the same 3.73 rear end. He gets 10.5-11 mpg while I get 11.5-12.5 mpg driving at the same speed. I'm not really impressed with his acceleration, nor with the noise. Do like the exhaust brake though. So I'm getting 10% better fuel mileage and right now diesel is a 25-40% premium where I mostly drive.

Something must be very wrong with that 2016 diesel. As with all my vehicles, I keep a log book in each and then enter the data into an Excel spreadsheet. I don't pay attention to the mileage displayed by the vehicle computer. The setup you see in my signature below consistently gets 13-14 mpg; empty it gets 18 mpg. I have never gotten less than 11 mpg, even towing when the truck and trailer grossed over 27,000 lbs. It is a manual tranny though, and has free-wheeling hubs installed, all of which help mileage.