How much more MPG would you get lowering your car 2 inches?

[blackjackel]

I ran an estimate of 1 MPG gain, and I calculated that it would take me 70 tank fillups to justify a $100 cost of lowering my car by two inches (springs).

If it saves just 2 MPG then the figure would half!

How much improvement in FE do you guys think I'll see by lowering my car?

Here's my math:

100 gallons x 1MPG saved = 100 miles (saved per 100 gallons spent)

100 miles (saved) / 42 (my current average MPG) = 2.38 (gallons saved per 100 gallons spent)

2.38 gallons (saved) x 4.5 (approximate current cost of gas) = $10.71 saved per 100 gallons

$100 (approx cost of lowering) / $10.71 ($ saved) = 9.337 (amount of times you need to save $10.71)

9.337 (amount of times) x 100 (gallons) = 933.7 (gallons before the mod pays for itself)

933.7 gallons / 13 gallons (current tank capacity) = 71.823 (tankfuls before the mod pays for itself)

[taco]

how about this lower your car for looks then the change for mpg wont matter as much

[Vince-HX]

my civic has struts and springs and they allow me to corner faster which really helps my EOC on certain parts of my commute.

Btw you also should include the cost of a re-alignment If you decide to mess with your car's suspension.

[blackjackel]

Originally Posted by Vince-HX

my civic has struts and springs and they allow me to corner faster which really helps my EOC on certain parts of my commute.

Btw you also should include the cost of a re-alignment If you decide to mess with your car's suspension.

re-alignment?

[cfg83]

blackjackel -

Originally Posted by blackjackel

re-alignment?

Because someone will be disassembling the suspension to install the shorter springs, you will need to get the wheels realigned :

Wheel alignment - Wikipedia, the free encyclopedia

You estimated $100 for the installation. If your estimate doesn't include alignment, you may need to increase the installation estimate to anywhere from $150 to $180 total.

CarloSW2

[IvanAndreevich]

Nevertheless, he has a valid question. Does anyone have any numbers before/after lowering?

[MetroMPG]

Ivan: not that I'm aware of.

Also, the in/effectiveness of lowering will vary from car to car as well.

blackjackel: you should add your vehicle to the garage so everyone knows what kind you're referring to in all your posts (it'll appear under your username).

[tjts1]

Alignment is free.
Pelican Technical Article: Home Alignment

[Big Dave]

I lowered my truck 3" in front and 6" in back. In addition I went to smaller tires up front to get another inch.

My truck went from 76" tall to 72" tall and I gained 1.0 MPG.

The truck also corners much better.

[bgd73]

I didn't notice anything upon my own experiments. Handling, maybe looks...

[geoff]

Just having the car lower shouldnt really affect the aerodynamics, any fuel savings would come from the fact that things like spliters are closer to the ground. I would tell you not to waste your time with it if you are that concerned over only doing it to break even after 70 tanks of fuel.

If you are interested :

1) Find out what springs are avalible for your car, make sure they match what you want. Some springs may lower the car too much, or too little for what you want. You also want to check the spring rate of the new springs, to stiff will be uncomfortable for a daily driver and can shake things loose on bad roads (over time). Others may be too soft and the car can/will bottom out over big dips or with more weight in the car. The cost of a quality set of lowering springs, for a street car, will range in price from about $150-250 average. Be aware that some cheap springs will be made of cheaper materials that can break or sag over time, or they might not be well suited for the application you are using. Since springs play a major roll in the cars ability to turn, accelerate and brake...PLEASE DONT CUT CORNERS AND TRY TO SAVE $$$ IN THE NAME OF SAFETY. If a spring was to break at highway speeds, it could very easily cause a serious crash.

2) If your not going to install them yourself, add in the cost of an install. If your just having new springs put in (keeping stock shocks and stuff) figure 2hrs of labor for a shop with the right tools, if you are having it done at the same time as something else (brakes, shock change, ect) it could save you some money since some of the disassembly will already be done for the other job.

3) I would HIGHLY recomend you replace/upgrade your shocks at the time you change the springs. Stock vehicle shocks (most of the time) are valved only for the stock spring rate and ride height. Lowering the car and/or having a stiffer spring rate (almost all lowering springs are stiffer) will cause the shock to opperate outside of its normal range. This will cause the shock to have a much shorter life span or fail outright. Bad shocks will cause the car to bounce over bumps and hurt the ride quality and handling. If your shocks have more than about 50k miles on them, chances are they are already not working as well as they should. If you replace the springs and also replace the shocks with new OEM units, it will be ok for a while, but the shocks will wear out again, and faster than with the stock springs...if you find a good shock to match to the new springs you the ride quality will be better, and the life of the shock will be longer than OEM shocks with aftermarket springs.

4) You might be able to get away without messing up the allignment too bad, but chances are you will end up with a car that is out of spec when the work is done. To get the most out of the new suspension parts, youll need to have the allignment re-set. If you want to take on the challenge, you can allign the car yourself and get pretty close to the right specs for camber and toe using the "string-box" method. Caster is a little harder to set this way, but caster shouldnt change much anyway. A bad allignment will speed up tire wear, can cause a drop in MPG and make the cars handling dangerous (something like too much toe out in the rear).

Sure you could find cheap/used lowering springs and have a buddy install them for around $100, but to do it RIGHT and get the most benefit from lowering the car...I would plan on spending $200 (springs) + $450 (shocks) + $100 (allignment) + 2hrs of labor (if your having a shop do the work).

[MetroMPG]

Originally Posted by geoff

Just having the car lower shouldnt really affect the aerodynamics

Lowering affects aero, regardless of the presense of splitters/dams.

It can reduce frontal area slightly, improve the fineness ratio (height/length), and improve Cd. Manufacturers do lower some vehicles specifically to improve aero.

See this thread: Does reducing ground clearance REALLY reduce drag?

Of course whether or not it will benefit a specific vehicle depends on that vehicle's starting point.

[PaleMelanesian]

It also depends on the kind of driving. If all the driving is stop-and-go city stuff, it won't make a bit of difference. If it's all interstate driving, it could make a big difference.

[jamesqf]

In my case, it would probably give me worse mpg, averaged over a year. The Insight's pretty low already, and if there's more than about 4-5" of snow on the roads, it becomes a very ineffective snowplow - which really kills fuel economy :-)

OTOH, I really wish I could figure some way to lower my Toyota pickup about 6", just to make loading it easier. Any mpg gain would be a bonus.

[cfg83]

Hello -

Which Lexus "auto lowers" at freeway speeds? How much does it lower and what are the claimed MPG gains?

CarloSW2

[aerohead]

Originally Posted by IvanAndreevich

Nevertheless, he has a valid question. Does anyone have any numbers before/after lowering?

I've never seen a specific breakdown.The really high mpg/low drag concept cars are lowered with active suspension,so they can still negotiate driveway ramps and such.They tell you what the Cd is with the "drop",however do not provide Cd for "street' configuration.If you want to slide your car under Darin's teardrop template,you could probably calculate the difference in virtual wake area,with and without the drop.Any 10% reduction in wake area would yield a 10% drag reduction,and 5-6% better mpg,at 55-70 mph,respectively, do to fineness-ratio alteration from drop.Search for" permanent Metro Kammback" to find Darin's template.

[aerohead]

Big Dave,those are useful numbers and I'm writing them down.Thanks mucho!!!!!!!!!

[MetroMPG]

Originally Posted by cfg83

Hello -

Which Lexus "auto lowers" at freeway speeds? How much does it lower and what are the claimed MPG gains?

CarloSW2

I believe I read about a Cd difference of .01 for the active suspension (which lowers the car 1 inch at freeway speeds) vs. the regular car. Sorry I don't have a link handy. I think it was the '06 LS460 (Cd .26)

[meemooer]

well... if you lift a truck the FE goes down, if you lower it, most guys get better FE.
So wouldn't it be the same way with a car?

[FunkSkunk]

Found a good price on a real set of springs here --> Intrax 25-1-010 - Intrax Lowering Springs - summitracing.com

HTH