Bad mileage myth?

Wow - I'd love to see how the 17"s look - got pics? (I'll check for your earlier posts...)

As for general mileage - you are in Tampa, right? Warm temps and mostly flat? That's very different than the low 30 temps and hilly terrain I've been struggling with to get up into the 50 mpgs here...
it was really nice this weekend to get into the 70s and not have to work so hard to get better economy. I was was getting 48 mpg without trying, mixed highway and city, but lots of hills.

Cheers!
Dave

 

I figure that your commute is mostly long distance highway. The heavier wheels would not affect your MPG as much as local city commute (due to repetitive accelleration - spin up heavier wheels). Yes, the re-gen braking may recapture some, but that is far below 100% efficient (you know that).

 

How are calculating your mileage? If your new wheel/tire combination has a different circumference, your odometer is giving you a different distance measurement. You will get a number but it is not necessarily correct. Do you have a way to check the accuracy of your odometer? WA state has mile posts along the highway.

Allan de

 

Quite right.

If the "17 inch" refers to the tyre radius and stock is 15", then there is an (17/15) underestimate by the MFD of FE = to 13%.

Addendum ... I think it is under, and not over ... but this is confusing my sleepy brain. AFAIK, the Prius computes distance by axle rotation * a presumed wheel Circ, and then divides by directly measured fuel injection. So the same real distance with a larger tyre will take a smaller angular rotation, and be falsely calculated as a shorter distance than actually traveled.

 

Deleted not quite relevant post.

(Missed the 17 inch wheels part)

 

Make your trips short in cold weather, and 30s MPG isn't hard to acheive, if that's most of your driving.

 

I find it easy to break the 40 mpg barrier and get worse milage! Just take your Prius on lots of short trips. Take my commute -- one mile, over an overpass (above a train track). Poor little Prius isn't even warmed up by the time I arrive.

But is this bad milage? Probably not. My other car gets 13 mpg average over this same route!

The "correct" answer is to walk or ride my bike to work. The weather has been too bad lately, but nicer weather is coming. Then my Prius fuel economy will magically jump!

 

The 15" or 17" would be rim diameter. Normally you use a different (lower) profile tire when upsizing the rims. Generally you can get within a couple of % of the original outside diameter. This is in the ballpark of tire pressure changes, different "same" size tires, or tire wear changes. Sites like Tirerack have calculators that will show the % gain/loss.

The main problem in plus sizing is that you are more likely to damage the rims and tires on potholes with the lower profile tires. Running higher pressures helps alleviate this. The handling is definitely improved (less side flex in the tires on cornering) and most people like the appearance (although I personally think it starts to look stupid when taken to extremes).

Most handheld GPS units give a very accurate speed and distance readout if you get a decent number of satellites locked on. This is great for evaluating how accurate your speedometer and odometer is before and after any tire change.

- Tom

 

nice look .-)

and love Your mod tread!!


ive been thinking of changing weels aswell when summer starts

ive been thinking of the O.Z racing rimms , the superturismo GT

this are suposed to be superduper light

friend of mine had older model on his alfa romeo , and they were amazingly light


http://www.ozracing.co.uk/Superturismo_gt.htm


just have to get the spec on them and se if they fit and exact weight



cheers

Andreas

 

It's baffling ain't it? I'd really like to go on a ride-along with someones who's in the low thirties or high twenty's. It would be really interesting to see what factors could lead to such low numbers.

 

I think you answered your own question without realizing it. "Daily 120 mile commute".
How many people do that? I drive 7.5 miles each way, and the first third I get about 25 mpg. Then the engine is warm and I get 50 or better the rest of the way, but so far it averages in the low 40's. Add a couple short drives in town over the weekend and it can easily drop below 40. And this is despite the fact that I drive conservatively, on a mixed suburban route with occasional stops, but not a lot of traffic tailgating me (so I can practice the P&G on the low rolling hills) and no >55 mph stretches.

But two other things I should mention. I bought my car last month, so it isn't broken in yet, and so far the temperature is in the low 30's during the day and mid 20's at night (Fahrenheit). I imagine after the first oil change and the warm weather that started last week it should be improving noticeably. And a longer commute would help my mileage claim, altho I would just end up burning more gas.

nerfer

 

I see bit of information on your MFD that, in my mind, explains it all.

Outside Temp. 84F

Living in a moderately cold climate, I can say that I've been AMAZED at how much better my mileage has gotten in the past couple days (when it's been somewhat warmer).

 

I too drive regulary 80 mph and am averaging 46.5 overall. Along with warm Florida temps, I credit following others at a moderate distance for at least 5 mpg at 80 mph.

My question is, Why Toyota didn't include ave speed next to ave mpg?

 

I have a similar MFD photo showing 50+ MPG...for 4 months during summer! Have to agree with the temp being a MAJOR factor. Even going downhill here when it's 10 degrees F, I rarely see 50 MPG.

Must move south....must move south...

 

You call 5 miles a short trip, I call a short trip 1 mile. In the congested big-city Northside of Chicago, everything is close. I drive to Target, the grocery store and dry cleaners since it's hard to carry big & heavy things. The colder it gets in the winter, the more likely I am to drive a short distance. A double whammy ! - more short trips and colder weather.

While it doesn't happen too often, I've had a few tanks in the 37-39MPG range. Overall, my lifetime average is about 45MPG, mostly because an occassional road trip carries more mileage "weight" - lots of miles in one trip vs. lots of trips with low miles.

In short, it's entirely possible to get less than 40MPG. If you're baffled, make a road trip to Chicago, maybe Boston or NYC, and make some short drives around town. Your experiences may be different, that doesn't make others' less believable.

 

temperatures play a HUGE part as long as AC is not used. the higher the temps. the better the mileage. i have tons of data on this.

 

Well, Doc, the other thing that I would imagine that you've got going for you is FL flatness. Your car can more easily maintain your target speed with fewer kWs. That allows you to have long periods of uninterrupted 50+ MPG. I bet that's more important than the temps (as you mention also).