Diesel vs Gas Engine? Better MPG When Towing??

[carl2591]

I know right.. someone always comes in with the torque vs HP comment.. too bad they don't different between gas and diesel engines.

here is info for 6.2L gas V8 from Ford
Raptor, 411 hp (306 kW) @ 5500 rpm, 434 lb·ft (588 N·m) @ 4500 rpm

her is info for 6.7L diesel V8 from ford 2016
Valvetrain: OHV,four valves per cylinder
Horsepower: 440 at 2,800 rpm
Torque: 860 lb-ft at 1,600 rpm

quite a bit of difference in RPM and HP vs torque.

again this is why most OTR trucks hauling 80K lbs use diesel engines vs gas engines.

HP and torque are both needed to get up the hill.

Originally Posted by Countryboy59

Horsepower is a measure of work done. Torque is a force applied at a distance. The horsepower/torque debate is moot. They are different units of measurement.

[gandttimes]

Originally Posted by JimGaskill

I began with a Silverado 1500 with max tow package towing a 27fb International. Gas mileage not towing was 16-19mpg. Towing was 9-10.5mpg. Truck pulled easily but could not use any cruise control unless in perfectly flat country. Any rise in the road would cause transmission to upshift. Truck performed nicely. Fuel range was about 160-175 miles. In July I changed to a Silverado 2500 with Duramax diesel. Now there is no upshift in transmission unless climbing a 5 degree grade. Mileage towing is 13.5-14 mpg. Without runs 19-21mpg. It is a larger fuel tank but my range has increased dramatically. Remember I am towing exact same trailer. This should give you an accurate real world evaluation of the gas vs diesel. I would definitely recommend diesel over gas if you plan to use your Airstream a lot. Can't comment on total overall cost for the life of the vehicle. I don't believe the gas will have the life of the Diesel engine. Hope this helps. Gas was a 2014. Diesel is 2016.

Jim, which engine and transmission was your Maxtow?

[JimGaskill]

It was 5.7 liter. Tow package has 3.73 rear axle and no option on transmission. Sorry, don't recall specs on transmission.

[Countryboy59]

Different tools for different jobs. Semi trucks run nonstop and need to last a million miles. They carry very heavy loads and accelerate those loads from a standing start. A gasoline engine would be huge, thirsty and impractical to do that job. Semi truck engines have very little in common with light truck and car diesels, unless you have a Cummins. If you put semi truck engines in light trucks you would not be able to afford one.

I recently visited Europe where many cars were diesel powered. They are gradually switching to gas because of emissions and manufacturing cost. I'm afraid the US may be heading that way soon. Guys where I live are getting the emissions crap off as soon as they are out of warranty.

[carl2591]

Not sure where you got the 6 months part of the maintenance schedule.


It does state "15K & duty cycle based" which according to manuals states "The engine oil change indicatory system is duty cycle based, which means the engine oil change interval may fluctuate dependent upon your personal driving style." With that said if you do a lot of heavy towing in mountainous areas then yes you may need to change oil at 6 months vs 15K miles.

this is from the cummins engine site on when to change oil and NO mention of 6 months is shown.

6.7L Cummins Turbo Diesel for Pickups (2016)
Maintenance

Maintenance intervals have changed over the years on several items, however, the valve lash adjustment remains the same at 150,000 miles (240,000 km) and the fuel filter replacement remains at 15,000 miles (24,000 km). The oil change interval is 15,000 miles (24,000 km) and is duty cycle based. This engine uses an oil change monitoring system which will display a message on the vehicle information center that alerts the driver to change the oil.
https://cumminsengines.com/showcase-...09#maintenance

It does not make sense to change oil at 6 months is you only have 3K miles and no towing, no sense at all.

Originally Posted by Bruce B

My 2016 Ram 6.7 Cummins has a 15,000 mile or 6 month oil service interval. There is also some maximum number of engines hours service interval too...
Now you know!
Bruce

[Toutsi 1957]

Originally Posted by JimGaskill

I began with a Silverado 1500 with max tow package towing a 27fb International. Gas mileage not towing was 16-19mpg. Towing was 9-10.5mpg. Truck pulled easily but could not use any cruise control unless in perfectly flat country. Any rise in the road would cause transmission to upshift. Truck performed nicely. Fuel range was about 160-175 miles. In July I changed to a Silverado 2500 with Duramax diesel. Now there is no upshift in transmission unless climbing a 5 degree grade. Mileage towing is 13.5-14 mpg. Without runs 19-21mpg. It is a larger fuel tank but my range has increased dramatically. Remember I am towing exact same trailer. This should give you an accurate real world evaluation of the gas vs diesel. I would definitely recommend diesel over gas if you plan to use your Airstream a lot. Can't comment on total overall cost for the life of the vehicle. I don't believe the gas will have the life of the Diesel engine. Hope this helps. Gas was a 2014. Diesel is 2016.

The added cost of exhaust fluid is only one to two cents a mile for those who are interested to know. My tow vehicle is a Denali HD Duramax 2016. The truck give me more satisfaction than the AS.

[dasams]

Originally Posted by JimGaskill

Truck pulled easily but could not use any cruise control unless in perfectly flat country. Any rise in the road would cause transmission to upshift.

What's the issue with the transmission shifting to increase engine speed and power? Is it mileage drop?

Originally Posted by Countryboy59

Guys where I live are getting the emissions crap off as soon as they are out of warranty.

Good luck to them passing the smog test. Just ask Volkswagen

[Toutsi 1957]

A half ton truck (1500 or 150) will tow any AS with the right engine and max tow package. The next question is the required payload you need. If you exceed the payload of a half ton truck you must go up to a 3/4 ton truck for safety and legal reasons. Selecting between a diesel or gas is then only a question of money. If you are capable of paying for a diesel. Go for it. It is better than a gas engine in all circumstances. This is the sequence of the reasoning. If you can buy a new 30' Classic you can afford a HD truck with diesel and go for it.

[hjnj]

Just throwing in my actual experience with 2015 Ford F-350 crew cab with 6.7 Diesel engine towing 2007 AS Classic w slide out. TV has about 20,000 miles. I know you are looking at a Chevy and not a Ford, but here are some things to consider.
1. Tows great - accelerates very well when needed. Pretty much like towing nothing at all. Maybe overkill, but I drive with confidence. Nice engine braking as well. (Had F150 3.5 gas Eco-Boost before and upgraded when we got the Classic. F150 mileage without towing was 15-17mpg.)
2. Mileage with F350 w/o towing - 16 (mostly HWY). Mileage towing AS Classic - 10.5 mpg overall but also mostly highway. Pretty big towing penalty - more than I thought with diesel, but I cruise around 70 mph. Maybe better if I had a lighter foot?
3. One aspect to consider that a friend told me, but I haven't verified. Supposedly, diesel has better desirability and resale value in the used market. Not sure if it makes up for the higher up-front cost or not.
4. One drawback with my configuration, which I believe has been addressed with Ford's 2017 model for you to consider with other brands is the fuel tank size. I have the 6.5 foot bed. This model annoyingly only has a 28 gallon tank. The full-size bed had a 40+ gallon tank. At 10.5 mpg, my truck towing the Classic realistically gives us only about 250 miles between fill ups which can be annoying.
5. Diesel fumes are not an issue. I am amazed at how much progress has been made at cleaning up diesel emissions with low sulpher and DEF. I am sensitive to diesel fumes as well and it is not an issue.

The good news is that both choices are great... Enjoy your Classic!

[slowmover]

Hjnj, if the MPG comparisons are at the same speed and under the same conditions, then a 35% drop from solo to towing is spot on. Industry norm is 40%

70 is too fast for a variety of reasons. Let me suggest 67-68 instead. This gets one around governed big trucks AND keeps one out of car traffic, all of which cluster together.

Being stuck in car traffic guarantees higher accident risk, more lane changes, and more acceleration and deceleration events. The morons (the 99%) are too stupid to travel except in packs.

Yes, aero drag claws skyward from 60-mph. But 70 will not result in shorter travel times than 67. So the penalties increase on several fronts.

I don't know what Fords are doing in terms of MPG. They've never been as good as Dodge (or last as long). A Cummins pulling a 27-34' AS (weighing from 7-11k) will see 14-16/mpg at speeds up to 65. It excepts the emission problematic years from 2008 until DEF tuned engines became available.

Drop a few mile per hour from travel speed, use cruise control constantly, and maintain a large leeway from other vehicles. This experiment should show highest MPG overall.

Stopping with a TT is at its limits from 65 (pretty well the max for a solo pickup). At 70, the time and distance to get below 50-55 mph (where the truck is less likely to turn over given remaining on pavement) is very high risk territory.

See Titan, Aero and Transfer Flow for larger replacement fuel tanks.

I average 15 with my one ton CTD and 35' trailer. At 80% of 36-gls, that's a reasonable travel range of well past 400-miles (7-gls in reserve). I'd like to have one of the replacement tanks as I believe 500-miles with reserve is ideal.

Good luck.


1990 35' Silver Streak
2004 555 Cummins

[hjnj]

Hi Slowmover,
Thanks so much for the advice! I am relatively new to towing, so appreciate having the benefit of your experience, and your advice seems very prudent. 65-67 will be my new running speed. I see that you have been on the forum since 2006 and have helped many others with your comments. Much appreciated.

Thanks also for the info on replacement fuel tanks. I was wondering if replacement takes were available.. Do you know if the replacement tanks are considered as safe as OEM, and also, do you think it would affect the warranty?

[Countryboy59]

Originally Posted by dasams

What's the issue with the transmission shifting to increase engine speed and power? Is it mileage drop?



Good luck to them passing the smog test. Just ask Volkswagen

No smog tests here in Michigan.

[slowmover]

Hjnj,

My knowledge about the tanks derives from other Dodge owners. Vehicle specific enthusiast forums.

It wouldn't be sensible for he aftermarket to supply a non-OEM compliant replacement tank, I'd think. One is then stuck with in bed tanks of which I'm not favorable towards as they raise an already high center of gravity.

The only Ford site I ever visit is "Powerstroke Nation", and then only due to their subforum on fuel economy. Another is "FTE".

Start with the manufacturer list first.


1990 35' Silver Streak
2004 555 Cummins

[hjnj]

Much appreciated. Will check out the options. 400- 500 miles between fill ups would be a big improvement.

[pappy19]

The new diesel engines are very much over hp and torque from just a few years ago. The new gas engines have more hp and torque than diesels did just a few years ago. What that means is if you are towing a monster 5th wheel, a 1 ton diesel may be your best bet. On the other hand, a 450 hp and 950 lbs of torque for a 30'Classic is totally unnessary. A gas engine is more than enough. A gasser oil change even at 5,000 to 7,500 miles, is generally only $40. A fuel filter every 15k is another $15. On the other hand, a diesel engine runs additional $8,000 to start and $200 per oil change with DEF every 5,000 to 7,500 miles, maybe more if you use Amsoil products. Fuel filters are $25-50 depending. Fuel costs will average .20-70 cents more and yes, diesels generally get 2-5 mpg better than gassers, but not significant to make a diesel needed to tow any Airstream. I've owned Ford and Chevy diesels and worked on pipeline projects where the Cummins-Dodge was very prevalent. Every species of diesel truck has one advantage or another, apples to apples. But, none of them are necessary to haul an Airstream. Any new gas engine, be it 1/2 ton up to 1 ton, setup to haul the weight, will do just fine. What doesn't work is some fool trying to convert a passenger car to haul an AS and think it's cool to be a minimalist. It will bite you in the butt.

[nrgtrakr]

Hello,

Our 99 Ford SuperDuty, diesel, 4x4, 4 speed automatic, xtra cab, short bed with shell gets ~20 mpg @ 65 mph empty, ~18 mpg towing our 75 Overlander 27' and doesn't know the trailer is back there (no equalizing or anti-sway hitch in use).

[Thiss]

Another vote for diesel. If the cost of the upgrade is a barrier, go check out a Ram with a Cummins. I was allowed to back out my ordered truck at no penalty. Not sure how the GM dealer to factory relationship is though.

[Thiss]

Originally Posted by Toutsi 1957

The added cost of exhaust fluid is only one to two cents a mile for those who are interested to know. My tow vehicle is a Denali HD Duramax 2016. The truck give me more satisfaction than the AS.

I can echo this. I have 6k on my new Cummins and still have a half full DEF tank.

[wbrisett]

Originally Posted by Countryboy59

I recently visited Europe where many cars were diesel powered. They are gradually switching to gas because of emissions and manufacturing cost. I'm afraid the US may be heading that way soon. Guys where I live are getting the emissions crap off as soon as they are out of warranty.

I travel to the UK multiple times a year for work, you're right they have a ton of diesel cars running around. Apparently the UK government had a big push many years back to get more fuel efficient and they saw diesel as the answer. It's the same in the rest of Europe.

Now the bad. It's been revealed that 97% of all diesel cars fail the Euro5 emissions test. This is the older standard. Only 7 of the 62 cars in a recent study passed the Euro6 standard (which still isn't as harsh as the US standard).

https://www.theguardian.com/business...-nox-emissions

Some of the vehicles were spewing more than 12x the legal limit of pollutants into the air!

The issue here is the standards have to get stricter, at least if we want to continue to enjoy this orb we live in and enjoy from our silver works of art.

I find it amazing that here we are talking about emissions as if they are evil. I don't know about you, but I enjoy watching my daughter enjoy the outside world when she comes with us camping. There's so little of it left that isn't corrupted by commerce and people. Even our National Park system is getting overrun by idiots seemingly bent on damaging things. I think the bottom line is we need to be good stewards to what we have. That includes the land, air, and water. It's why we enjoy our Airstreams, to get outside (or maybe it's just part of AS crowd... I have seen people who are OK with simply parking in RV parks, and that's another segment of people I suppose).

Call me crazy, but I'm OK with the extra emission testing and equipment that goes on with diesels. I haven't (yet) seen it affect my performance pulling my Airstream, and I absolutely love the comfort of my 2500 HD and won't go back to a gas model until we give up hauling our Airstream around (and that's not likely to happen).

-Wayne

[crispyboy]

Wayne,
Being a conservation minded person I can absolutely agree with what you are saying about enjoying clean air, water etc.... there isn't a person alive who doesn't want this.
The problem in the diesel world is that the emission standard on diesel vehicles from 2007 thru 2011 (approx.) had real growing pains. Most of the time the consumers were really getting raked over the coals with emission systems that worked part of the time if the engine was used within certain parameters.
For example where the systems worked:
- diesel emission systems would work ok when a truck was used on the open highway towing heavy loads or a truck would have to be worked often enough to keep the soot levels low enough in the exhaust system.
For example where the system had trouble:
- those using a diesel emission vehicle for short runs, around a jobsite with idle time or lots of starts and stops -
- utility crews who must keep trucks idling/running at a jobsite for long hours
- bucket trucks
- agricultural use etc.....

The repairs are extremely expensive (ask me how I know), the power and fuel mileage were greatly reduced from previous years.
You will understand when it hits you in the pocketbook. My truck is stock as I enjoy the clean, stink free exhaust but I know it is on borrowed time. A new exhaust system is several thousand dollars.
This is the main reason why people delete emission systems in the generation of trucks from 2007 thru 2012 and people want a reliable vehicle.
The diesel of today have come a long way but still have some growing pains and issues with reliability. The repairs almost always involve the multiple sensors in the exhaust, egr valves or soot in the turbo. The cost of all this technology has driven the cost of the diesel truck thru the roof in my opinion.
Why do you think VW fooled with the emissions on their cars - so they would be more reliable for the consumer and less warranty cost for them.
There is a balance between the emission requirements and common sense but the two have yet to meet..........