Remove spare tire, how much mpg gain?

Interesting. You have regular Prius owners removing their spare tire to reduce weight and improve fuel mileage. Plug In owners adding spare tires to their Prius. I did. Are we confused?

 

Weight matters less on flat land. So it all depends on the terrain you drive.

 

I'm guessing that the donut spare weighs ~30 lbs. max.
Add the jack, maybe 35 lbs total.

Weights removed affect mpg when accelerating, basically from stops and up hills,
although changing the direction of a vehicle is an acceleration. That said:

"...if the vehicle weight decreases by about 156.26 pounds (or roughly 150 pounds),
the fuel economy will increase by 1 mpg."

This figures out to a 0.22 MPG gain for a 35 lb weight reduction.
Another source says 0.4 MPG.

It's far more likely that you'll be seeing meaningfull passive MPG gains as the result of
rising Outside Air Temps ( up to ~80 degF)...

or from actively changing your driving by trying "driving without brakes," inflating
your tires to 42front/40 rear, or lowering your typical cruising speed by 5 MPH.

 

35 Lb is about 1% or the cars mass, so I'll estimate about 0.5% improvement in MPG. So yeah, about 0.25 MPG sounds good.

Edit: Trying to add an adjustment for "typical" hills and descents, or acceleration and deceleration, I'll add another 0.2% to that estimate.

So I'll estimate 0.7%, which I guess is going to be around 0.35 MPG savings for the average driver.

 

Gut the interior of the car and get rid of every ounce possible. You'd surely increase MPG's.

NOT for me.

Getting towed for just a flat tire, even if you have road service is NOT an option for me.

I even bought full size spare.

 

How much does the engine weigh?

 

I was carrying a full size spare over the winter and didn't notice much difference in mpg when I removed it.

 

Aye, it's not worth the inconvenience or risk of being stranded. If you are competing then go for it. Otherwise keep the spare.

Just buy more efficient tires when the time comes.

 

^^^ here is an equation I stole from the Chevy Cruze chats.
My intent was to post this this on the spare tire thread but I will offer it here.
Think it says +50-lbs is -0.6 MPG at 50 MPG for 3165 car weight (PiP).
<:ASIDE>

...here's an equation that approximates the WT vs. MPG trade-off:​

​

(MPG2/MPG1) = (WT1/WT2)^0.72​

...where:​

​

MPG1= prior fuel economy, mpg​

MPG2= new fuel economy, mpg​

WT1 = prior weight, lbs​

WT2 = new weight, lbs​

​

​

• addendum: equation is valid for vehicles in the 3,000± weight class (per GM engineer).​

Read more: http://priuschat.com/threads/better-economy-at-the-top-of-the-tank.123507/page-2#ixzz2Sa7lhW00

 

So if you put the weight of the Prius (about 3400 lbs assuming typical passenger + luggage loading), and the added weight of the spare at 35 lbs as estimated above, this equation gives a result of 0.73% loss. Almost exactly the same result as my previous estimate. This proves I'm good, haha

 

We already knew that.

 

Only proves you qualify for work at Government Motors. If you have not yet received an email from Toyota, that probably means the Toyota engineers have a better equation!

Made me realize part of our MPG problem is our Prius is now in serious GP (grand parent) service. We have two hefty car seats - must be 50-lbs each empty - and a big stroller in the hatch. GP service also means shorter trips. But we like it.

 

WOW, if one could always drive downhill - what great mpgs!
Seriously, removing the spare tire do not increase mpgs.

DBCassidy

 

It shouldn't make much of a difference to reduce the cars weight by 35lbs

 

less than 1 mpg i'd venture...

 

Even if it really did improve mileage by 3 MPG I don't think I'd feel safe parting with it. I have triple-A roadside assistance and a cell phone, but what if I'm in a location where my cell phone doesn't work? I'd be stranded, possibly for hours. I'm getting about 51 MPG average right now and I feel like that's a lot to me. I won't sell my peace-of-mind for a few extra cents in savings at the pump.

 

I will not leave my spare tire. LOL.

 

This is a funny thread because I did remove the spare tire on my old departed SUV for weight savings BUT if you can get 35lbs out of the Prius you gain about .73mpg? I just lost 21lbs over the past 4 months. So if I lose 14 more, I will gain .73mpg just from that? lol

 

No, the estimate was about 0.7%, so realistically more like around 0.3 to 0.35 MPG.

BTW. It's interesting that the "googleleadservices" ad at the top of this thread is now showing a fat/weight loss ad for me. Oh well, at least it's a change from how they usually "profile" me and display ads to "meet mature women".