Gas or Diesel

[C_B_]

My Son is looking to get a 2015 Ford F-350 CC SB.

He's trying to decide between the 6.2 gas or pay extra for the 6.7 diesel.


He currently has a 6.0 diesel so he knows how the diesel pulls.

Question is how good will the 6.2 gasser do pulling his Cedar Creek 362BBS with a GVWR of 14,000 lbs.


Thanks in advance for your input.

C.B.

[Tystevens]

Sport45 wrote:
I think most diesel owners are more in love with the turbocharger than the fuel. They just don't realize it.

A NA diesel is a wheezing pig on mountain passes, same as gas. My late father in law pulled his TT with a 6.2l diesel Suburban and I can tell you from experience it was no powerhouse. The gas engines of the day would easily outrun it. They couldn't touch it for fuel mileage though. And diesel was much cheaper than gas back in the day.

Good statement! I've been thinking this very same thing since I started towing with my turbo'd Ford Ecoboost. Which, surprise, tows a lot like my turbodiesel did! It has less torque than my Duramax, obviously, but I love where the torque comes in, and how level the curve is. Just like my diesel! I love that I can tow a 7% grade at 65 mph in 4th gear at 2500 rpms with the Ecoboost (the Duramax did it in 5th gear at 2k rpms), as opposed to 2nd gear and 5k rpms struggling to keep above 50 mph. Of course, I don't have to deal with the power drop off caused by the altitude, either, as said pass tops out at about 8k ft. I think I just like turbos!

Those older NA diesels were something, and not necessarily in a good way! My grandpa's Ford 6.9 and a family friend's 6.2 Suburban, both of which I drove a bit in my teens, turned me off to diesels for years! Yeah, the mileage was good, but the lack of power was remarkable - the gas 350 in our family's Suburban felt more powerful than both by a long shot. It wasn't until I drove my grandpa's 5.9 Cummins (yep, a turbo!) until I 'saw the light,' so to speak.

[Dog_Trainer]

A diesel is more efficient when pulling for the simple fact that the HP is made at a much lower RPM. I HAVE RUN MANY THOUSANDS OF MILES next to a MH of similar size and weight as mine when we run the flat land I cruise at about 1850 RPM which is right in the sweet spot. I think the Chevy 8.1 motor that is in the other mh gets a couple mpg less running the flat land. The real difference comes when accelerating and climbing I will climb a 4-5 % grade at about 2300 RPM while a gas MH will be in the 4000 + range the diesel using much less effort and fuel when climbing or pulling a heavy load. While the article stating the performance being similar it also states that flatness of the HP curve is a consideration this is where the diesel has it all over a gas motor. I will concede that many trailers , 5ers and MH will do well with the Gas motor but there comes that weight point where the gas motor will no longer be a good choice. The big MH today are all Diesels, Busses such as the over the road kind are all diesels, the trucking industry is all diesels not because you can't make a big HP gas motor but because the efficiency and torque to move the load is insufficient in a gas motor. Without torque value and RPM there is no such thing as HP. I think the value stated in the above post is tongue in check as the measurement is Torque X RPM / 5250 = HP

[pnichols]

Equations can help see the truth better if you look at them from various angles.

I thought the equation in the link article was this 😉 :

Torque (ft-lbs) = horsepower x 5252 / speed(RPM)

By the way, here quoted are the last sentences from the link:

"In summary, there are a lot of misconceptions about horsepower and torque. Remember that it depends on the gearing, horsepower and flatness of the horsepower curve - but very little on the torque number by itself. If two engines have the same horsepower, with the proper gearing they will perform very similarly, but the same general statement can’t be said for two engines of the torque."

[Sport45]

rhagfo wrote:
Just got to ask, have you ever driven/towed with a diesel?

Yes, I have. It was a Suburban with a 6.2l NA diesel pulling a 26' TT. We had to stop at just about every pullout on the climbs in order to let traffic pass.

It was a lot cheaper to operate than the big block gassers that were passing us though.

[john_bet]

rhagfo wrote:

pnichols wrote:
Please read the link above your post.

Just got to ask, have you ever driven/towed with a diesel? If you have you will understand, it would need to be within a reasonable age and size of the gasser for comparison. I think you would be surprised.
The biggest issue with diesel is Ford has given them a bad name, and denied warranty clams for their faulty design. Yes, the other diesels have had issues, just like gassers, but not to the extent that Ford has.

I guess a good comparison would be my 5.9L Cummins to a 6.0L Chevy/GM gaser with my 5er and a 3.73 rear gear. The towing red line would be 2500 RPM for both. HUM????

[rhagfo]

pnichols wrote:
Please read the link above your post.

Just got to ask, have you ever driven/towed with a diesel? If you have you will understand, it would need to be within a reasonable age and size of the gasser for comparison. I think you would be surprised.
The biggest issue with diesel is Ford has given them a bad name, and denied warranty clams for their faulty design. Yes, the other diesels have had issues, just like gassers, but not to the extent that Ford has.

[rhagfo]

pnichols wrote:
Please read the link above your post.

Yes, it states;

"Horsepower = speed (RPM) x torque (ft-lbs) / 5252"

Guess HP is dependent on Torque

[pnichols]

Please read the link above your post.

[Vulcaneer]

rhagfo wrote:


Vulcaneer, You are wasting your time and effort trying to explain the difference between towing with a lot of HP vs. a lot of Torque.

Boy!!! Are you right. But the more he posts, the point becomes more obvious.

There are places where high rev's are nice. Towing my RV is not one of them. But in his Motorhome, it is. Good for him. And with that 20 Valve V10 and 4:56 gears, I bet he likes the fuel mileage too.

To each his own.

[pnichols]

The equation I showed above came from the science and engineering world but still might be wrong. Note that it says nothing (nor does it need too) about efficiency - it just shows the relationship between crankshaft torque and horsepower output.

Please research a bit and post for us the proper equation for a diesel engine ... but please make sure that the equation includes somewhere in it a value for "torque" and a value for "horsepower" so that - using the math rules for changing around equation structure - that "torque" winds up on the left side of the equal sign and that everything else winds up on the right side of the equal sign.

I'm always open to learning about the proper diesel equation showing the relationship between diesel crankshaft torque and diesel horsepower output.

Thanks in advance.

By the way, maybe this article can help make things pretty clear:

http://lainefamily.com/hp.htm

[Turtle_n_Peeps]

pnichols wrote:
I wonder what makes some think that diesels don't "gobble the fuel" when pulling loads up long hills with their turbos boosting away???

The energy has to come from somewhere .... most likely the fuel tank.

By the way, here's the engineering equation for where horsepower comes directly from. Notice that the equation does not care whether one is talking about a diesel or a gasser engine that's making the torque from power -> horsepower. But what it doesn't show is that a diesel pulls DIFFERENT, not BETTER than a gasser when both have equivalent horsepower. Preference is everything and Detroit has made sure (other than Ford with the good old V10) that the preference winds up being diesel because they (or maybe the EPA) refuse to make a pulling gas engine:

Torque = Horsepower X 5252 / Revolutions Per Minute

(For one exception example, see my earlier post above about a 1965 Ford I once owned that had a pulling gas engine.)

More than like because a diesel gets about 30 to 35% better fuel economy.

Or a gallon of diesel has about 13 to 15% more energy/ gallon than gasoline.

Or a diesel engine has virtually no pumping loses because it has no throttle plate.

So are you saying with your HP formula there is no difference between fuel burning rate with different fuels? If so, LOL.

Here is some news for you:

BTU's for diesel is right around 129,500/ gallon

BTU's for gasoline is right around 112,00/ gallon.

BTU's for methanol is right around 57,000/ gallon.

BTU's for nitromethane is right around 47,000/ gallon.

Now, do you really think you will get even close to the same fuel mileage if you use lets say methanol instead of gasoline?

Or do you think you will use around twice the amount of methanol than that of gasoline because gasoline has around twice the energy/gallon?

Like I said; with my 600 hp supercharged engine I burn about 1.25 gallons of gasoline / 1/4 mile. That is 5 gallons/ mile........not 5 miles/ gallon. :E

Good luck selling that to the public for a towing vehicle with those MPG figures. :B

[mlts22]

What is interesting are the dyno specs from clapping two low PSI turbos on the venerable Ford V-10. It will need a new tune to understand that it isn't a NA motor anymore, but even a slight boost in pressure to compensate for altitude does wonders for this engine. The engine has a lot of cubic inches and low RPMs, so even a 5-7 PSI in boost would make the V-10 compare favorably to a diesel. It won't BE a diesel, but it will give them a run for their money, albeit at a higher RPM range.

IMHO, it is a matter of won't than can't here. Ford's EB proves that one can make a gasser with the torque/power curves similar to a diesel.

[pnichols]

I wonder what makes some think that diesels don't "gobble the fuel" when pulling loads up long hills with their turbos boosting away???

The energy has to come from somewhere .... most likely the fuel tank.

By the way, here's the engineering equation showing where torque comes directly from. Notice that the equation does not care whether one is talking about a diesel or a gasser engine that's making the torque from horsepower. But what it doesn't show is that a diesel pulls DIFFERENT, not BETTER than a gasser when both have equivalent horsepower. Preference is everything and Detroit has made sure (other than Ford with the good old V10) that the preference winds up being diesel because they (or maybe the EPA) refuse to make a pulling gas engine anymore:

Torque = Horsepower X 5252 / Revolutions Per Minute

(For one exception example, see my earlier post above about a 1965 Ford I once owned that had a pulling gas engine.)

[Sport45]

Turtle n Peeps wrote:

Sport45 wrote:
On the other hand, 15psi of boost would have a 6.8 liter engine acting like a 13.6 liter (830 cubic inch) NA. That'd certainly be fun... 🙂

And would gobble fuel like a drunken sailor. :R At around 475 HP my engine eats about 1 gallon/ 1/4 mile run at WOT.

But wasn't it fun? 😉

I never said it would be thrifty...