Re: Fuel efficient tow vehicles options?
When you posted this question, I knew you were really going to stir things up.
My work experience is 24 years with a major domestic auto manufacturer, and I used to get into the middle of more car/truck deals in a month than a top salesman would see in his career. I am a car guy--through and through.
For pulling an 18'-22' boat and spending $18k-$20K: Go after a 2 year old domestic 1/2 ton truck with a "supercab" second seat. I would suggest a Chevy C1500 or Ford F150 with the regular 5.3 engine or 5.4 engine. (Those GM variable displacement motors are junk.) Go for the middle trim cloth seats, as the leather seated versions are too much $ and usually 4x4's. I would go for a two wheel drive unless your lake has very poor quality boat ramps. Two wheel drive trucks will perform well on the highway and get approximately 18-19 mpg in moving traffic. These trucks will give you good value because they will hold their value if well maintained and taken care of.
I say 2 wheel drive, because of their lower initial cost and simplicity. For the price difference, you can pay for 40-50 wrecker calls. At $110 hourly labor rates, I don't want to pay the price to maintain a complicated drive system.
Notice that I didn't include Dodge Trucks. While they are perfectly good trucks, they just don't hold their value 2 years old or especially 5 years old. Their automatics are not reliable as the other brands. If you wanted to purchase a Dodge, I would want the newest body style--in a crew cab. Dodge dealers are not as successful as Ford/Chevy, and this brand truck is just not as good a value as Ford/Chevy for the long run.
The mid size trucks would do the job if they had V-8's, but they're really not much less expensive than full size trucks--and much harder to sell on the used market. The Chevy Colorado is just not too popular, and the Tacoma's a gas hog (simply put.)
You could go an Expedition or Tahoe (with the right engine), but they're pretty expensive new and used. A good alternative is a 4.6 engine in the last model of Explorer--an especially excellent used vehicle for the money. The V-8 Explorer will get around 21 mpg highway, and they'll pull a boat trailer well.
My tow vehicle is a 3/4 ton crew cab diesel 2 wheel drive leather seated redneck limo--with a chipped engine putting out 700 ft. pounds of torque. I pulled a house down with it last year--no kidding. These trucks may cost $48K new, but I'm getting 20 mpg @ 70 mph and they have a 500,000 miles lifespan. For $18K, you can get an 03 model diesel that still has more miles left in it than a brand new gas 1/2 ton. These trucks are great values, as they are very trouble free and can be passed down to your grandson.
The next generation of new truck engines is now coming into the market. Ford's supercharged V-6 is a real towing monster that still gets 22 mpg. Their new Coyote engine (out of the Mustang GT) is $750 cheaper, and it's about equal in towing power (real world.) Their base V-6 is almost 300 horsepower, and would also do the job. Ford's 6.2 engine is also available in a 3/4 ton. Chevy has a somewhat new engine lineup, but their 6.0 engine with a 4.10 axle is a 10-11 mpg guzzler. But, we're talking much more than $18K for any new truck.
Good luck in your truck search!