Aerodynamic mod to improve fuel economy

Sippery lines are only helpful for highway speed on flat road. If you spend most of your driving time in or around cities, or up and down mountain passes, then you'll see diminishing returns, especially if said aero mods are adding weight.

For instance if you look at EPA estimates on the 95 Tacoma, you had a maximum of 26 mpg highway with 2wd, versus 20 mpg highway just by switching to 4wd with the same motor and transmission. The city mileage shows a much smaller difference, with maximum 19 mpg on a 2wd versus 16 on a 4wd.

Case in point, you can save 6mpg just by losing all the 4wd bits. That's a roughly 23% fuel savings, and the truck is cheaper anyway. But this also assumes all highway driving, refer to my first point.

Aero mods are cool, but just do some simple math and you'll find more often the best money solution is to just choose a simpler vehicle.

 

A 95 tacoma 2wd has better aero than the 4wd, smaller tires, and lower. Are the final drive ratios the same? A ≈25% difference just for 2wd vs 4wd is significantly higher than other vehicles I've seen where it's usually less than 10% for otherwise identical vehicles.

 

All the good ideas are already taken. Personally I just chose routes that are downhill ever place I go.
https://carbuzz.com/news/this-aerodynamic-bubble-roof-ford-f-250-is-weird-as-it-gets

 

That's a really interesting point. As far as I understand it, the two main factors in fuel consumption are aero and weight. Since the effect of aero increases with speed and the effect of weight is more noticeable with start/stop driving, can we take the city/hwy numbers as representative of weight/aero respectively? In that case it would seem in the comparison between the 2wd and the 4wd 1995 Tacoma the aero component has a greater effect on fuel consumption than the added weight.

 

The 4wd 95 Tacoma sits approximately 4" higher and has wheels that are 5" larger in diameter. That's a huge difference in body roll and wheel inertia, which is why the mileage drops so much. It's not uncommon to lose 5-8 mpg when you lift and increase the wheel size, especially when offroad tires have higher rolling resistance from the larger treads. Lots of forces fighting you when you optimize for offroad.

 

^^ This. Lately I've been driving 61 mph on hwy and achieving 21 mpg vs 17-18 mpg at 65 mph. 2" lift with a rooftop basket and canopy.

 

Tire pressure . A few extra P.S.I. ... a good tire pressure gauge in the glovebox.

 

I'd say "proper" tire pressure, not "a few extra PSI"

under inflated tires are obviously bad, but that doesn't mean over inflated tires are good. Over inflating your tires creates handling and tire wear issues.