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Running 70-75 mph towing my 4500+ lbs boat (tall windshield) I average 15-17 mpg. Running 50-ish in construction zones it's 22-24 on level ground. On the highway I'm usually using cruise control but not T/H mode unless it's hilly or a lot of traffic that I need to constantly adjust to. Anything under 65-70 I'm in 5th but above it's in 6th.

But I'm "cheating"...engine is the 2.8.
it's strange why diesel guys always exaggerate their MPG.
 

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especially since I have a duramax 6.6L diesel that doesn't even get 15-17 mpg towing a 4,500 lb boat at 70-75mph. so you definitely "cheating" with that 2.8L...
 

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Discussion Starter #43
Hey Chum since your calling me out!
I just unhitched an hour ago and DO NOT USE CRUISE
What is it you were complaining about again?
Ahhh yes......lol

12.31 MPG US over the last 50 miles. Same terrain as the OP.

Because you want to attribute it to cruise doesn't mean that cruise is what caused my fuel consumption.

I think we are done.
 

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Discussion Starter #44
Well it sounds like you answered your own question. Why did you post asking for help?
If you go back and re-read my OP, I wasn't asking for help. I was relating a story. The 1st response, post #2, nailed it. And no, it wasn't cruise.
 

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Indeed, the takeaway I was after wasn't the RPMs but that I have the same MPG and RPMs towing with and without cruise.


Also, folks need to keep in mind that RPMs play a little part in fuel economy, it's all about engine load. Just because the engine is turning higher RPMs doesn't automatically mean it's burning more fuel, especially if the RPMs are where the engine is the most efficient. Similarly, lower RPM can translate into higher load on the engine and higher fuel consumption compared to a higher, more efficient RPM.


Also, running the V6 at 4,000 RPM for extended periods of time isn't abuse and isn't going to cause the engine to wear out "twice as fast" as running at 2,000RPM. Higher RPMs while towing heavy/high-drag trailers with a gas engine are just part of the deal and one reason why I hate towing with gas vehicles, not because it's bad but because the constant engine noise at higher RPMs just wears on me.
So an engine running 50% more rotations and spitting in fuel 50% more often can get better fuel mileage than the other running a lower RPM? Being a life long car guy and pretty adapt to common sense and technical information that is news to me...

98% of the time higher RPM equals higher fuel consumption. Any deviance to that will almost always be attributed to low rpm lugging. You also have to consider at higher RPM you are also getting higher loads of oil and bearing losses compared to low rpm driving and other added draws to an engine regardless of the efficiency point of the engine. There is a reason cars have tall over drive gears because running at higher RPM's is quite inefficient.

Tyler
 

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I think aero was an issue for you as well as "pushing" your truck's limits with the cruise control. Sustained RPM of 4000 would drive me crazy (not from the money for gas but just the fear of the abuse I'm putting the truck through). I recently towed a similar weight from Kansas City to eastern Iowa over long rolling hills with my 2017 ZR2 (which are notorious for crappy mileage due to big tires, heavy weight, and I've leveled mine in the front so aero is worse) and averaged 13 mpg while generally rolling at 70-75 mph. The key to me with rolling terrain is to maintain momentum - coast down the hills (let it roll!) and don't beat the crap out of it on the uphills (you might lose 5-10 mph but return to your desired speed on the next flat / downhill). Car weighs about 3100 pounds and the trailer was something over 2000 pounds.






So you over loaded your truck, why not just drive it? That is what those cars are made for...

Tyler
 

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Over a 10 hour drive that's nearly an hour of added drive time...

Tyler
Yes, nearly an hour for 10 hours of driving. That's negligible. Also, the travel time difference is going to be even less once you account for the fewer number of fuel stops needed due to the increased fuel economy.

So an engine running 50% more rotations and spitting in fuel 50% more often can get better fuel mileage than the other running a lower RPM? Being a life long car guy and pretty adapt to common sense and technical information that is news to me...
You seem to be forgetting that just because an engine is turning higher RPMs doesn't mean it's injecting a higher volume of fuel. An engine that is operating at its most efficient RPM will consume less fuel than an engine running at an RPM outside that window when under load.

Fact remains, it's load on the engine and where the engine is most efficient that determines fuel consumption, not RPM.

98% of the time higher RPM equals higher fuel consumption. Any deviance to that will almost always be attributed to low rpm lugging. You also have to consider at higher RPM you are also getting higher loads of oil and bearing losses compared to low rpm driving and other added draws to an engine regardless of the efficiency point of the engine. There is a reason cars have tall over drive gears because running at higher RPM's is quite inefficient.

Tyler
98% of the time, eh? Care to provide a reference for that number or did you just make it up? No need to take my word for it, experiment for yourself when towing a trailer (Since this thread is about towing). I've already done this over the nearly 10,000 towing miles I've done with my 2.8 as well as with previous vehicles.

It's all about engine efficiency, lower RPMs doesn't always mean more efficient. The most efficient RPM is typically right around the peak torque RPM, engines tend to become less efficient as RPMs move away from that point, both with higher and lower RPMs, when the engine is under load (again, such as while towing...which is what this thread is talking about).

You also need to consider BSFC vs absolute and fuel economy vs fuel consumption.

To say that "98% of the time, higher RPM equals higher fuel consumption" is patently false because it doesn't take into account where a given engine is most fuel efficient or has the lowest fuel consumption for a given load and the engine's power output.

That's like saying "98% of the time, higher vehicle speed equals higher fuel consumption." I'm sure you know that's nonsense, right? Same goes for the statement regarding fuel consumption vs RPM.

You cannot make a blanket statement like that and assume that it applies across all engines and loads. It simply doesn't.
 

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it's strange why diesel guys always exaggerate their MPG.
Not exaggerating at all. 15-17 is what I get all day long towing my Skeeter. That’s what I got over a 1500 round trip to northern WI. These little 2.8l engines get great fuel mileage. Sorry you guys are jealous of such a small engine.
 

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Those of you with tuned engines and access to ECU data can do a little science experiment for the rest of us.

You have access to how much fuel is being fed to the engine with reference to load and engine speed. You can estimate a BSFC curve off of that. At that point, you'll know where peak efficiency island of the BSFC curve is. At that point, the dash already has a tach; all you need is a vaccum gauge or some other ECU data display to show load real time... pick the gear that lets you drive your truck at your desired road speed while staying closest to the optimal engine speed vs load region.

Don't sit here and armchair engineer, do some science on your own!

 

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Those of you with tuned engines and access to ECU data can do a little science experiment for the rest of us.

You have access to how much fuel is being fed to the engine with reference to load and engine speed. You can estimate a BSFC curve off of that. At that point, you'll know where peak efficiency island of the BSFC curve is. At that point, the dash already has a tach; all you need is a vaccum gauge or some other ECU data display to show load real time... pick the gear that lets you drive your truck at your desired road speed while staying closest to the optimal engine speed vs load region.

Don't sit here and armchair engineer, do some science on your own!

Nah, that would require effort. :LOL:
Not exaggerating at all. 15-17 is what I get all day long towing my Skeeter. That’s what I got over a 1500 round trip to northern WI. These little 2.8l engines get great fuel mileage. Sorry you guys are jealous of such a small engine.
If I were towing all the time I'd have the diesel. I just can't stand how slow it is. I am curious though, how much does that skeeter weigh? I'm taking my boat up to conniticut this weekend and I'm trying to gauge what I'll get mpg wise. I'm thinking maybe 12. Lots of hills and traffic the way I'm going.
 

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If you take a look at the torque/rpm curve, your best mileage will normally occur where you are running at the top of the torque curve.
 

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Nah, that would require effort. :LOL:

If I were towing all the time I'd have the diesel. I just can't stand how slow it is. I am curious though, how much does that skeeter weigh? I'm taking my boat up to conniticut this weekend and I'm trying to gauge what I'll get mpg wise. I'm thinking maybe 12. Lots of hills and traffic the way I'm going.
I haven't weighed the boat and trailer yet. But my aluminum Lowe was 3100-3200 lbs. The fiberglass hull is 600-700 lbs heavier, the trailer another 700. The outboard 100. So, I'm figuring the Skeeter is about 4500-4600 lbs. Every time I drive by the Cat Scales with it it's full of all my fishing gear so i wouldn't get an actual weight on it, only the boat package. If I'm towing long distance I try to put all my gear in the cab or truck bed to keep it off the trailer. Local towing everything is in the boat.
 

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Discussion Starter #55
Picked up my 2019 diesel a few weeks ago.

First day driving to work, 100km commute, mostly highway 7.4 l/100km (31.8 mpg). Day 2 was 7.2 l/100km (32.7mpg). Best to date 6.9 l/100 (34.1mpg). I am usually on cruise around 110 kmh / 70 mph.

I have had the camper out already, on a 800km round trip to the Mattawa area, hillier area than where I am. Average speed was around 100 kmh / 62 mph. Trip consumption averaged 17.9 l/100km (13.1 mpg).

As soon as I got back I hitched to a 6*12*6 enclosed trailer to move my daughter to Oakville, probably 3,000 lbs loaded. 14.1 l/100km (16.7 mpg) on the way down, 13.2 l/100km (17.8 mpg) on the way back empty. Other than the crawl through Toronto, I was pretty steady at 110 kmh for most of it.

Very happy I got the diesel.



IMG_20190828_091318.jpg

IMG_20190822_141953.jpg
 

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I have the 3.6L V6 in my '18 ZR2 Crew. I get 17.5-18.2 in daily driving, but pulling my Triton TR20 with a 225 Yamaha Vmax on the weekend pulls it down to 13. I haven't put it on the scales, but I'm guessing 3,700-3,800 lbs loaded out?
 

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Terrain makes all the difference! Pulled my 4500 lb travel trailer home from camp yesterday and for the first time, I filled the fresh water tank -55 gal - and decided to take an older, rougher road home. Going to camp on a newer, smoother road with allot more hills, I averaged 9.5 mpg with empty tanks at 60mph. Yesterday, the older, rougher but FLATTER road yeilded 11.7mpg at 60 mph with an added 440 lbs on the front of the trailer where the fresh water tank resides. All in, I'm easily over the 5k pound mark. Even though the older route was rougher, it was well worth the beating on my pocket book. Also, I measured how much farther my truck drops with the added weight and it was only another 1/2" for an overall drop of 1 3/4" from the stock ride height. My next long road trip with the trailer is going to be as much away from the interstate as possible. Running easy at 55-60mph is allot less work for me than running 65-70mph, less hills and allot fewer big rigs flying by pulling the truck and trailer sideways. The longer, slower trip takes more time, but I was so much less fatigued by the time that we made it home. Super pleased with this latest trial and outcome.
 

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4K RPM is just over halfway to redline and just shy of 60% of the V6's 6,700 peak power RPM. The V6 is a sporty high specific output engine and it is designed to spin. To equate this to the diesel, which has a 3,400 peak power RPM and (I believe) a 4,500 RPM redline, the equivalent 4,000 RPM V6 engine speed on the diesel engine is 2,100 (59% of peak power) to 2,700 (60% of redline) RPM, which is hardly "abuse".

In both cases, the engines are spinning up to a speed that they need to in order to deliver the power they were designed to deliver. From where I sit, I would rather run a V6 at 90% of it's max RPM vs. the diesel. The V6 sings on top while the put upon diesel at 4,000 RPM says WTF are you doing man!

It is kind of interesting, I have a buddy with a 6.7 Ford Powerstroke and the 6.7, which is a beast of course, is also way revvier than my Canyon's chill little 2.8. The big 6.7 rips past 4K and seemingly loves it, all while punting that big truck around handily and sucking down a prodigious amount of fuel. Ripping around in a 6.7 is impressive indeed.

If towing with your truck, I would put it in M5 and drive at 60ish, proactively gaining some speed approaching hills to give it more reserve RPM on the way up. Your mileage improved from 6.7 to 9.4 by dropping the speed from 65 to 56 mph. That is a 29% increase in fuel efficiency in exchange for a 14% drop in speed, well worth it I think.

Ah yes, the quadratic nature of wind drag, so many brain numbing equations to consider. Wind drag increases in a dramatically progressive fashion with speed. That is all I have for you though, I suck at math :rolleyes:
 

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4K RPM is just over halfway to redline. The V6 is a sporty high specific output engine and it is designed to spin. To equate this to the diesel, which has a 4,500 RPM redline, the equivalent 4,000 RPM speed on the diesel engine is 2,300 RPM, which is hardly "abuse". In both cases, the engines are spinning up to a speed that they need to in order to deliver the power they were designed to deliver.

If towing with your truck, I would put it in M5 and drive at 60ish, proactively running it faster approaching hills to give it more reserve on the way up. Your mileage improved from 6.7 to 9.4 by dropping the speed from 65 to 56 mph. That is a 29% increase in fuel efficiency in exchange for a 14% drop in speed, well worth it I think.

Ah, the quadratic nature of wind drag, so many brain numbing equations to consider. That is all I have for you though, I suck at math :rolleyes:
FWIW, the diesel redline is actually 3,400-3,500RPM when under power and 5,000RPM for grade braking.


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Mine did 14.2 on my recent 300 mile trip. There wasn't much left to use after 4300 or so. Kept it in the torque band and it was fine. It didn't like the last hill to get to the lake though. More rpms would have helped but the person in front of me was going too slow to wind it up.
 
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