Help MPG thoughts talk Please!

Hello,
I'm new here! my wife and I picked up a 2012 tacoma rag.cab 4X4.We have about 2000 miles on it we do mostly drive highway 55 we have the 5 speed st. shift tranny. worst tank was 20.4 best tank was 27.5 most of the time we got 24.5 to 25.5.. Happy with that.. But we installed a ARE Cap not the lowest one but then the tallest one.. it's about 4" taller the the cab but well desined in that there is a good strong slant to the trans-isun.. Sorry.. But found that the MPG droped to a good stady 22.4 MPG now on most all tanks.. The cap onlu weights 140lbs it does have a roof rack systom but there only small 1 1/4" round bars.. ( They can come off) I would have thought that the cap should have inproved MPG just a tad.. I'm trying to use 5th (over drive) when I'm free going and if I have to give it some gas to make a hill I try and gain 10mph or so before hitting the hill od down shift if responce is low when I get on the gas.. I try to drive not to stress the motor and bog it down by being in the wrong gear. Please you thoughts on my MPG? I really would like to see 25mpg on most fill ups.. That would make me happy.. Thanks George

 

Slightly tough read but here's my thoughts. The cap plus rack adds an extra 140+ lbs so obviously your dragging around more weight which means you'll burn through more fuel. Despite your thinking that it aids in aerodynamics it doesn't really translate to saving fuel though.

You're only a couple mpg off where you'd like to be so if it means that much to you, take the topper off when not in use? Else you may just have to live with it.

Above all, your driving a truck not a Prius so good gas mileage is hard to come by.

 

Shut yer trap, I get 11mpg so your whining about getting 22.5mpg aggravates me.

If you wanted better mpg you should have bought prius.

 

if you want the bed covered just get a tonneau cover, light weight and will help with aerodynamics, or just fold the tailgate down...

 

Well he wanted a truck, so he didn't buy a prius. Just because you get bad MPG for things you've done to your truck/how you drive, doesnt mean somebody else can't be dissatisfied with their MPG.

OP: Take the bars off, that should help a little. You'd be surprised.

 

Didn't mythbusters bust that theory?

 

Its the topper w/ rack.
My tacoma had a thule rack/no topper & lost mpg.
Your mileage sounds excellent though.
Mine never saw 20 ever. (V6/4x4/DC)

 

They did and tailgate down is worse for MPG's.

x2. The rack might be hurting you more than you think. I've got a topper with a 3" rise over the cab and I get 20 MPG with a V6 double cab (a little better than I was getting with just a tonneau).

 

If your goal is purely MPG's and your not worried about cost, you can get lightweight engine pulleys. The NST brand is top rated.

 

As someone mentioned it is more than likely the rack. They are known to really disrupt the airflow since it have to go over and under.

When I ride in my work van I can see my mpg drop when ladders are on there, they weigh very little but are horrible for airflow.

Not sure what rack you have or if you use it all the time but try taking that off and track mpg to see if it is the cap or the rack.

 

Most people are seeing a 1 mpg difference

 

What about the lighter flywheel, that would probably be just as, if not more effective.

Are there issues with engine balancing though? I read that some vehicles don't do well with lighter pullies.

Also, 1 MPG gain and a cost upwards of $300, the payoff is about the life of the truck.

 

It isnt the weight. You could add 1000 pounds of lead bricks and its effect would be negligible. same with light weight pulleys and flywheels -- those would let you wind the engine up quicker, but wouldnt affect fuel consumption.

This matter is 100% aerodynamics. You have increased the frontal surface area, and the aerodynamic profile. The big flat wall you now have for a back end is creating a massive zone of vacuum that you are pulling around.

Removing the roof racks will help, but if you want to make it good, you will have to ditch the lid.

 

Where do you get your information from?? Put 1,000 lbs in the bed and I promise you the MPG's will go in the shitter. I get what you're saying but your delivery needs some work. Also, for the 4 banger, the added weight would have more of an impact vs. the V6.

If the engine is equipped with lighter pullies and a light flywheel, it will let it spin up quicker but will also increase MPG's because you have less mass to get spinning and keep spinning within the engine. This means the engine isn't working as hard to produce the same amount of power to the wheels, which means less fuel consumption. It won't be a huge difference but lightweight pullies and flywheels do affect MPGs...

 

Tailgate down does not improve mileage.

 

Guess you're no fan of Sir Isaac Newton, eh? First law says that you will keep moving in the same direction forever unless affected by a force... i.e. aerodynamic friction. I guarantee that a weight increase will not increase wind resistance in and of itself. It cant have an effect on fuel consumption except during acceleration. OP says highway driving constant 55 mph.

 

According to... mythbusters, who are unparalleled HACKS. I saw that episode, and their experimental controls were absolutely inadequate. There was far too much reliance on "foot on gas", and an assumption that a Ferd will have a constant and predictable fuel consumption.

Not saying that their results were wrong, but that they didn't come anywhere near to actually proving it.

 

Holy hell, you really want to try and argue that one?!?! Newton's law of 'An object set in motion will stay in motion' only applys where there are NO outside forces. In the physical world we live in, you not only have wind resistence, but you have gravity, which you seemed to have conveniently forgotten about... More weight in the vehicle means more friction on moving parts, you'll squat your tires making more friction between the tires and the ground, more friction means more heat which makes things less efficient, etc. etc. all of which take more power to overcome. You WILL burn more fuel maintaining speed with a higher load, end of story.

Don't argue Newton's laws with an engineer...

 

Extra 140 pounds. Roof rack imparts additional air drag. The cap may too. Aerodynamics on pickups is a tricky science. What you might think will help actually hurts. Case in point, the mythbusters thing.

 

I suggest that you would be wise to heed your own advice. Newton's first law most certainly does apply. 2nd law, gravity does not apply since it is perpendicular to the motion. You want to start measuring how much extra friction there is against the bearings? Not even worth consideration.