Mod Efficiency and Cost

[1engineer]

I like to look at the "Lifted Pic" thread every now and then to see what type of cool things members are doing to their vehicles. I have noticed questions every now and then on "what mpg's" people are getting after the lift and mods. I want to attempt to explain what happens to the "newer" members who are thinking of modding their vehicle so they go in with "eyes wide open" before picking their mods. I have not modded my 4Runner much but in the past I have heavily modified many vehicles. The 4Runner is no different than every other vehicle in respect to basic physics. I wanted to start a new thread with this so other threads would not go off topic. Here is a question asked in the "Lifted" thread:

What kind of gas mileage are you guys with lifted 4R's getting before and after your lift?

I will be brutally honest:

If you lift it, you will lose efficiency
If you add bigger tires you will lose efficiency
If you add heavier wheels you will lose efficiency
If you add skid plates you will lose efficiency
If you add aftermarket bumpers you will lose efficiency
If you add any gear like drawers you will lose efficiency
If you add a cool Gobi roof rack you lose efficiency due to weight AND aerodynamics.
And the list goes on...

Basically if you lift it you will lose efficiency because you effectively are punching a bigger hole through the air and any added weight is a penalty too. In addition to adding weight in/on the vehicle by adding the weight in such items as wheels or tires there is an ADDITIONAL penalty of efficiency by having to accelerate the unsprung mass.
All of these items, taken by themselves, will not cause too much of a loss. You migt be able to make a slight mod from the above list and not see any efficiency penality. When you add them up however you could possibly lose up to 30-40% over your stock fuel efficiency. So if you average 20 mpg now with a stock unit you could go down to 12-14 mpg.
Let me put it to you this way: If you drove a stock unit getting 20 mpg 15K miles/yr with gas at $3.50/gal you would spend $2,625.00/yr. If you drove the same amount with mods getting 14 mpg you would spend $3,750.00 or a additional cost of $1,125.00/yr. Your call.

With that said, the mods I listed above can be extremely functional and needed depending on your application and look really cool to boot. I personally enjoy reading the mod threads and believe me, we have a talented group here who have turned their already capable stock vehicles into extremey capable modified machines. For the most part the guys who did these mods knew their efficiency would drop and were OK with that and the added cost of operation. I just wanted to start a thread for the new guys who might be modding to keep these things in mind. Thanks.

 

[Ducmonsta]

Awesome explanation!

It's hard to believe people still inquire on how much fuel efficiency you'll lose. It's also the same person that whines about $4.00/gallon but is ok with $6.00/cup of coffee.

I, personally, knew what kind of loss I was getting into. That's also why I've tried to stay away from the "what kind of mileage" threads. I'm happy to break the 14mpg number on my truck. I didn't buy it for fuel economy.

 

[lamber74]

Thanks for the explanation 1engineer.

To add to your point regarding tire sizing:
Not only do you have to consider tire weight when up-sizing your tires, you also have to consider the width of the tire. Increasing the width from a 265 to a 285 with then increase your contact pad and therefore take more energy to overcome from a stop and also increase the drag on the car during coasting.

Like you mentioned, I hope that anyone getting into modifications will understand that most things we want to do to our SUVs are not going to improve fuel economy.

 

[Hawaiian4runner]

Thank you!

Finally someone who knows what they're talking about! Not a bunch of dillusional babble about getting 25 mpg on their lifted 5th gen. Sure going downhill I get 35+ mpg but I get about 12 mpg in town. On the average I get 16.4 mpg. Much better than my Honda Odyssey and infinitely cooler. Can't knock the minivan. Most practical vehicle around for carrying people but at best, it is a minivan It is pure physics. I too am an engineer and agree that one of the biggest impacts is unsprung weight. Hurts performance, mileage, handling you name it. Big nobby tires increase rolling resistence tremendously but in the end, if you care, don't do it. 4runner is a very capable wheeler bone stock. Gotta replace the stock tires and you are good to go. Almost guaranteed to get a flat on those stockers if you do any kind of off roading. I mod stuff cause I like the look or functionality and it's fun. Can be a costly hobby but everyone needs toys. We should never out grow having fun! Yes. You will lose gas mileage. Yes the 4runner is not the most refined SUV out there. It is body on frame. It is heavy. It's a 4runner. Thank God!

 

[Davemon]

I understand 1engineer's point about the taller profile of a lifted 4runner creating more drag, thereby reducing gas mileage. But does anyone have any idea how much the components in your garden variety lift package (let's use the Toytec Ultimate lift, just for kicks) add to the vehicle weight, vs stock components? I've always been curious just how much more say Bilstein 5100s weigh, vs the stock shocks. And how much more the Superflex coils weigh, vs what comes stock. I can't imagine the difference would be huge, maybe 5 or 6 lbs total. But if anyone has hard numbers on this, I'd like to hear it.

 

[Jaker]

I understand 1engineer's point about the taller profile of a lifted 4runner creating more drag, thereby reducing gas mileage. But does anyone have any idea how much the components in your garden variety lift package (let's use the Toytec Ultimate lift, just for kicks) add to the vehicle weight, vs stock components? I've always been curious just how much more say Bilstein 5100s weigh, vs the stock shocks. And how much more the Superflex coils weigh, vs what comes stock. I can't imagine the difference would be huge, maybe 5 or 6 lbs total. But if anyone has hard numbers on this, I'd like to hear it.

I'm installing my Icon Stage 6 lift next week. I will weigh my Limited's X-REAS system and post back with a comparison.

 

[JohnJerk]

Tell us more about incremental reduction in MPG with various mods based on empirical data. I want stock size AT tires (Nittos, I guess). What will that do to my 20 MPG average? 18-19? And then if I did 2" lift, where would I be? 16?

 

[characterzero]

I understand 1engineer's point about the taller profile of a lifted 4runner creating more drag, thereby reducing gas mileage. But does anyone have any idea how much the components in your garden variety lift package (let's use the Toytec Ultimate lift, just for kicks) add to the vehicle weight, vs stock components? I've always been curious just how much more say Bilstein 5100s weigh, vs the stock shocks. And how much more the Superflex coils weigh, vs what comes stock. I can't imagine the difference would be huge, maybe 5 or 6 lbs total. But if anyone has hard numbers on this, I'd like to hear it.

negligible.

same as going out to eat with the fam - you think you get notably less MPG on the way home with 5lb of burrito in the gut?

 

[phillyd2]

Horse Puckey! There I said it. I modded and lost nothing! I still need to fill up the tank when it reaches Empty, just like before.

Good post! But don't think it will stop the questions :thumb3:

 

[1engineer]

Tell us more about incremental reduction in MPG with various mods based on empirical data. I want stock size AT tires (Nittos, I guess). What will that do to my 20 MPG average? 18-19? And then if I did 2" lift, where would I be? 16?

Unfortunately, individual cases cannot be characterized. For example:

I notice your location is in the higher altitude region. What is your gas milage at sea level? This link Gas Mileage Tips - Driving More Efficiently gives you but a few variables that influence fuel economy from another 4Runner owner in, say Florida. You will notice it says (and I paraphrase) "every 100 lbs added leads to a 2% drop in efficiency." I think for our vehicles that could be a little less than 2% but not much. Add the bumpers and skid plates and you could be going from your 20 mpg to 18 mpg. Point is many factre influence your gas milage. My above post was to inform on what will happen as you add weight and lift. You WILL lose, how much depends on the individual.

My AT tires in stock size are over 1" wider than what came on the 4Runner. I have only noticed a marginal decrease (less than 1 mpg) in efficiency after 5000 miles on the new tires. I will know more as time goes on.

I did not buy a 4Runner for maximum efficiency. With that said I do want it to perform at expected efficiency of around 20 mpg. If I wanted max I would have got a little tiny car to drive lol.

 

[Davemon]

negligible.

same as going out to eat with the fam - you think you get notably less MPG on the way home with 5lb of burrito in the gut?

This is what I was thinking. I don't expect weight to be a real issue until/unless I start adding skids, bumper, winch, etc. I'm more worried about tire/wheel weight affecting my mileage. I'm hoping when I upgrade, I can offset the increased weight of the LT tire with a lighter wheel. Mileage may not take a real big hit. Anyone know the weight of the stock SR5 wheel?

 

[1engineer]

Horse Puckey! There I said it. I modded and lost nothing! I still need to fill up the tank when it reaches Empty, just like before.

Good post! But don't think it will stop the questions :thumb3:

You are probably right but we now have a thread to refer to these folks.
Oh, your 4Runner definitely suffers in the efficiency department. My post was more directed to those who use theirs as a daily driver lol.

 

[Ducmonsta]

This is what I was thinking. I don't expect weight to be a real issue until/unless I start adding skids, bumper, winch, etc. I'm more worried about tire/wheel weight affecting my mileage. I'm hoping when I upgrade, I can offset the increased weight of the LT tire with a lighter wheel. Mileage may not take a real big hit. Anyone know the weight of the stock SR5 wheel?

I don't know if I think it's funny that this is in THIS thread or I'm glad you didn't start a completely new one.

 

[Antman]

.....
If you add a cool Gobi roof rack you lose efficiency due to weight AND aerodynamics.
And the list goes on...

I see what ya did there :cowboy:

Nice contribution, BTW!

 

[Davemon]

I don't know if I think it's funny that this is in THIS thread or I'm glad you didn't start a completely new one.

I debated

 

[offroadingatc]

I must be missing something here.

Asking approximately how much mileage loss you could expect after X mod seems like a very reasonable question, infact it seems absurd to not ask.

 

[x67934]

I am sure there are many folks on this site who are very pleased with their results after modding their trucks, however it seems every forum I am a member of people comment about how most modifications do not actually make vehicles better.

I think for the majority of people if they did the analysis they would chose not to lift, upsize tires, and install roof racks etc. The truth is most of us do not have a $30k truck to use strickly for recreation, so take an honest look at the miles you drive even if you off-road every weekend I bet it only makes up 10% of the miles driven annually. Is the modest improvement in off road capability achieved through a 2 inch lift worth losing even 1 mpg?

 

[Ducmonsta]

Is the modest improvement in off road capability achieved through a 2 inch lift worth losing even 1 mpg?

If it makes you:guitar3:Then YES! I don't care about fuel economy. Otherwise, I would have bought something else.

 

[DDM4]

1Engineer is correct in the entirety. Every time you modify something, you are changing a variable in an equation toyota created. In nearly all cases, this will result in reduced fuel efficiency. The math is final on that subject.

That being said, if the added cargo capacity of say a roof rack increased your ability to reduce the trips it took to take crap to the work site, well then, you'd simply have to run the numbers. Taking some liberty with the above scenario.

Personal satisfaction from self expression (sounding like a hippy here) by modifying a vehicle and making it your own is as old as the automobile itself and, impossible to measure. If a lift makes you objectively more satisfied with your vehicle, milage be damned, no one can argue with that. Go for it!

For me, stock specs for most vehicles fit my needs. If they didn't I would look at another vehicle that did or I suppose modify if it were the only available option. For myself, I don't think I know more than Toyota engineers (or any manufacturer's engineers) so I tend not to meddle with their math much.

 

[Jaker]

For myself, I don't think I know more than Toyota engineers (or any manufacturer's engineers) so I tend not to meddle with their math much.

I may not know more than Toyota engineers. However, I'm not constrained by corporate executives telling me an end product has to be within a certain price range for a particular demographic.

The fact of the matter is that if engineers were actually able to design an end product to their best of their ability with all the latest tech/gadgets with no price target in mind, you and I wouldn't be able to afford it.