Are My 17" Wheels Killing My MPG's...?

I'm pretty sure my short trips to and from work is what's killing my mileage, I get some longer trips on the weekend and saw my mpg go up nicely. Went up to 41 on the avg. Mpg and started going back down when I got back into my work week

 

I had a 2012 Prius 5 with factory 17" rims/tires- 100% factory.
My lifetime average for the six months I owned it (11k miles on the odo) was 50.1MPG.
Yes the speedo over reported my speed by +2 mph. The speedo read 60 the car was actually going 58mph.
There is no way to correct the inaccuracy due to tire size.

 

According to this document, 17" wheels reduce MPG by about 2.5-2.7%:

 

Nice find. Must be miles per imperial gallon.

 

I believe the oem 15s are in the teens.

SCH-I535

 

17'' wheels make more drag on the road and can cause a slight less mpg. I am getting around 48 mpg with three adult passengers in the car.

Check the following:
1. tire pressure ( i have 33psi on the rear wheels and 35 psi for the front wheels, check the driver door label for tire pressure )
2. spark plugs ( they should be changed every 120,000 miles or so -- see your car manual for specific schedule for your vehicle )
3. Oil type should be Toyota 0W-20 original oil ( wrong oil can change your mpgs and damage your engine )

 

Perhaps you can exchange your wheels/tires with his for a week or so? That way both of you will see what impact the wheels/tires have? After swapping, I would fill up the tank and check pressures so there's as more of an apples to apples comparison.

 

I believe this!

S0 basically, if I'm getting 50 mpg with my 17" wheels, I would expect to get 51.3 mpg with 15".

This sounds more reasonable than what others have suggested.

 

I have 2013 with 17" stock wheels. The elevation and speed of your route makes a tremendous difference. My daily commute to work (about 6 miles) I get 50-60 MPG (depending on temp of course) but on the way home using the SAME route I get only 36-42 MPG. The hills, traffic lights and such do make a big difference.

 

We've got the Canadian Touring model with OEM 17" rims, came with Michelin Pilot 215/45R17. Those are not indicated to be LRR, but they seem to roll pretty good, maybe a special OEM version? Anyway, our driving is a real mix, a fair number of short trips, and I've been tracking calculated mileage pretty much since we bought it.

Accumulated mileage currently is 5.1 liters/100 km (translates to 46 miles per US gallon). That's coming out of winter. With good thoughts and tail winds it'll sometimes push down to 5.0 (47 mpg) by the fall.

 

I just put on 17s on my Prius C - you can expect anywhere from a 2-7 MPG difference. I usually get in the mid to high 40's right now, whereas before I could hit 50s on a good drive. There is a huge drive difference however compared to stock 15s. Solid grip and stability, improved cornering, more shock absorption.

4DD5D333-108E-4E02-910B-3ECB6A75A46B by So_Jah_Seh posted Oct 15, 2019 at 11:24 AM

 

I wonder if using lightweight forged wheels will help much with the mpg considering it should be much lighter than the conventional stock wheels. I know that it costs a lot, but I'm wondering.

Posted via the PriusChat mobile app.

 

I'm confused by the bold bit; are you saying more shock absorption with lower profile tires on larger diameter wheels? I would say the opposite.

 

Our red 2011 Prius IV bomber came with 15 inch wheels. I bought a set of 17 inch Persona wheels without tires from a member of this forum about a year after we bought our Prius. After some research, I bought, a set of 205/50 17 inch tires for the wheels. In Maine you want every inch of tire sidewall. Roads can be broken, especially in Spring. The Persona wheels are about 23-24 pounds. Not light. The tires were Pirelli Cinturato P7. I lost about 2 mpg at first, but the tires broke in after 2,000 to 3,000 miles and mpgs came up by almost 1 mpg.

I ran the tires at 38 psi front and 36 psi rear. The tires wore well. I kept them at optimum pressure by checking them at least every 2 weeks. Temperature variations in Maine are big, so tire pressure could bounce around quite a bit. I also keep the load in the car at minimum. I don't use the car as a storage unit. Run light and you improve efficiency. Check your engine's air filter and intake plenum including the resonator under the air filter for debris. Critters like to build nests or store food in there.

Check your 12V battery under the hatch floor passenger side. A weak 12V battery will bring your mpgs down. 12V batteries typically last 4 to 5 years. Push it longer and you risk lower fuel efficiency.

Make sure your alignment is spot on and try not to take off like you're in a race car. Same with stopping. Don't impede traffic, but try to drive as smoothly as you can. I had to deal with hills in my commute. Accelerate down hill when safe to do and let the excess speed bleed off some on the uphills if they are short roller. I see a lot of people accelerate going up a hill, actually increasing their speed and then use their brakes all the way down to the bottom of the hill. Then they repeat accelerating up the hill again. Use gravity to your benefit when you can do it safely.

The biggest fuel waster is high speed. Leave a reasonable amount of time for your commute. It took 25 minutes to drive my commute to work every day. I didn't have traffic, it was all rural roads. I gave myself 35 minutes. That eased the drive significantly.

Try to use Top Tier gasoline. You can google Top Tier Fuel for a list of Top Tier brands. Additives in Top Tier gasoline actually help keep your engine's internals a little cleaner. Top quality 0-20 synthetic oil is a must for efficiency. Driving with windows closed is important. You get better mpgs with windows rolled up and the A/C on than windows down and A/C off at speed over 45 mph. Make sure all the under car covers are buttoned up so they don't act like flapping sails under your Prius.

My lifetime average mpg average with our red 2011 Prius was a tad over 51. That's calculated at the pump, miles driven divided by gallons used. We did quite a few Interstate trips with this car at 70+ mph (didn't want to get run over), so if we could have traveled a little slower, the lifetime mpg would have been a bit higher. My normal day to day commute and errand running would let me get 52 to 54 mpg when I kept it off the Interstates.

If you want maximum Prius mpg, you should go with the light 15 inch Prius wheel with a good LRR tire.

All the suggestions that everyone has made so far will help you get better fuel efficiency.