Advice needed on new truck

If you're buying a new truck then I'd say all 3 makers are doing pretty well right now. If your talking about a used truck the stay away from Ford 6.0 and 6.4 diesels. Also stay away from the Chevy Duramax in '01 thru '04.5. These years it was the LB7 and had lots of injector problems. Dodge trucks (gas and diesel) up until the introduction of the 68RFE had lots of automatic transmission problems. I would go with a manual unless it's new enough to have the 68RFE or now the new Aisin.

Diesels should get better mileage. The newer ones don't do as well as the older ones. (Thanks EPA).
My '01 Chevy 4x4 dually had an 8.1L gas engine and got about 10 mpg.
My '05 Chevy 4x4 dually has a Duramax diesel engine and gets about 16 mpg.

Your questions are all good ones but there's really no definite answer on an internet forum to any of them. Everything you get is going to be opinion based. If you're really serious about upgrading to a newer/bigger truck invest 20-30 hours or more and read through posts on various forums, shop sites for prices, check out reviews from the pros (road and track, etc.) and make a decision based on what you find.

After investing the time the decision becomes easy. You'll end up with the right truck. Wander into some dealership and buy the first thing they push on you and most likely you'll end up disappointed. 20-30 hours sounds like a lot of time but you can pretty much count on making $100 an hour or more when you consider how much a wrong decision would cost you.

I don't think I would want to take a CNG truck to Yellowstone NP and then try to find fuel along the way. There are not that many CNG fuel stops near a National Park. It might be fine if you only go limited distance, and always have a place to refill.

I drove a CNG Honda car, the problem it needed fuel every 90 miles. So you drive like 10 miles out of town, then notice that the last person driving it left only 1/2 tank in the car, and your trip might be 45 miles. You have to return to the nearest fuel station, fill it then be able to drive to your meeting or conference.

I know someone who drove a CNG combo truck from Long Beach CA to a confrence in Reno NV. Yes he made it on CNG, he was trying to say "I made it" and stopped in Bakersfield and Fresno, and Sacramento for CNG refills. Had all kinds of adapters, and those cities did not bill him for the fuel. (Billing for 10 - 12 gallons of $1.20 fuel would have been a headache) Anyway his truck would also run on the factory 19 gasoline tank too.

If you have your heart set on both a 3/4 ton and fifth wheel with a 1,500 - 2,000 pound hitch weight, probably should also stick to the lighter gas engine trucks - especially if you will buy used. The newest trucks have much higher GVWR, so might have plenty of cargo capacity, however the 2004 and earlier trucks had low cargo ratings, and the 2,000 pound potential hitch weight can use up more cargo rating than most 3/4 ton trucks come with.

Lets say the truck has a 8,800 pound GVWR and at the curb it is 7,000 pounds, crewcab with lots of options on it. You can only carry 1,800 pounds of people, cargo, and other things in that truck. Better to look for a 2005 and later F-350 with it's more generous 11,000 or 11,500 pound GVWR, and they can carry 4,000 pounds in the F-350 version or 3,000 pounds (about) in the 3/4 ton F-250 version.

What to stay away from?

Lets just say a lot of F-250 and F-350 owners of the 6 Liter diesel and 6.4L diesel sold them cheap to get rid of them. Potential problems are that the oil cooler and exhaust recirculation cooler leak around 100,000 - 120,000 miles. If replaced, and they never leaked, no problem. However one leak means a potential $15,000 engine replacement. This is because coolant will leak into the engine and destroy it.

THe GMC 6.6L engine has proven very reliable. The 5.9L Cummings found in the Dodge trucks has been much more reliable than the truck it is mounted in. Ford's new 6.7L found in the 2011 and later trucks is also a great diesel engine, and very quiet as well. It also comes with the higher GVWR, and high cargo ratings.

Gas engines? Well the 5.4L found in the F-250 and F-350 has 300 HP, should perform as well as your toyota does. The V10 6.8L is a little more power, and is used in 24,000 pound motorhomes, 26,000 pound GVWR F-650 trucks, even with CNG in the larger dump trucks. It is rated at some 360 HP or a little more. But fuel mileage will be less than the F-350 with a 5.4L engine.

I have towed a 7,000 pound generator with a 1994 F-250 and 351" engine. This was factory rated at only 175 - 200 HP, so the 5.4L has much more power than I had, yet still the truck did fine.

Fred.

I've had the Chevy w/gas 6.0L for 12 years/185000 miles and now my daughter has it to haul livestock and as a daily driver with just routine maintenance. I have now had the Ford V10 for 3 years and it just requires routine maintenance. I think the stories of mechanical problems w/American trucks are just rumors.

If you stay within weight rated for a particular truck, you'll be fine. Just find one that fits your butt and the your better half loves.

Mileage differences, especially towing will be minimal.

Reliability - the big three are all in the ballpark of each other.

No one tows with a CNG powered truck.

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1) For reliability from the big three I would say they're all pretty much equal.
2) For gas vs. diesel it mostly depends on personal preference, a diesel will pull a bit better and get better mileage while towing then a comparable gasser. But a gasser will pull whatever it is rated for but at a higher RPM to keep it in its powerband.
3) It used to be true that diesels would get much better MPG then the gassers of that year, but with the new emission equipment on diesels that gap has narrowed to maybe 1-4 MPG stock-for-stock
4) I have no experience around CNG trucks but would imagine that it would be very similar to towing with a gas engine. The worry I would have with that is finding fuel stations that stock it as I know of only one around the area I live that sells it.

About like asking which cola is best. I like Dodge Ram 3500 Duallies, but somebody will chime in that they pulls 18k pounds with a Ranger. Be warned.