rxonmymind

My commute takes me on a 180 miles loop daily. Filled up as normal and went on my way resetting the mpg. Coming up at the half way mark I was at 250 miles and at the line between half and quarter tank I was at what I normally would have to fill up at 330 miles. I made it to 420 to a tank before having to fill up again. 19 mpg vs 24.
This happened one other time in my Toyota Sienna having gone, get ready...500 miles to a tank. That time I called my wife asking if she refilled the tank for some reason. She hadn't.
Bringing this up to my coworker one related a story where he drove returning from vacation from LA to his home in his tank of a truck and averaged 25 mpg where he normally got 19. He couldn't figure it out.

Do you have a similar story?

Hoovey689

iTrader: (16)

Temperature, under/over inflated tires, fuel type, dirty engine air filter, summer gas vs winter gas (different additives) and more variables could factor to varying fuel economy.

mmarshall

Yep, all of the things that Hoovey mentioned....plus road conditions (rain and snow adds drag to the tires), average speeds, traffic density/stop-and-go driving, how much weight is in the vehicle, and, of course, one's driving habits with the right foot. Plus, a small chance that the trip-computer figures are goofing up or not reading correctly.

bitkahuna

iTrader: (20)

had a bit of trouble following your story... when you said between half and three quarters i think you meant between half and a quarter (as in 3/4 empty)?
and "19 vs 24" you mean you normally get 19 and this time you apparently got 24?
but from the sienna story i gather you got better mileage than usual on the rx.
gas consumption can be many factors, some mentioned. others include traffic, your avg speed, your driving (speed up, slow down and more/less accelerating on grades), eco/normal/sport mode in your car, weather (temp, humidity, heat, wind all factors), and on...
but 19 to 24 is a huge difference if all else very similar.

blacksc400

iTrader: (4)

I can go between 190 to 360 miles depend on local/hwy driving ratio. Too many factors to take into account.

rxonmymind

Yes. Thanks for catching that. Same gas, same route, same speed etc. Wild. I'm scratching my head. Today around town it's back to normal. Before the week starts for me I'll fill up again. Fingers crossed it'll happen again.

riredale

If I go 55 I get 30mpg. If I go 75 I get 24mpg.

So if I go 75 but with a 20mph tailwind, I will get 30mpg. The biggest factor in highway mileage is wind resistance. Most people are stunned at how badly carrying a couple of bicycles on the roof kills fuel mileage.

BlackLexRX

If you see the variation consistently from fixed points A to B and back from B to A it can be prevailing wind flow and direction. Case in point, I used to travel from Colorado back East to visit family. Crossing Kansas heading East I could get 28mpg's in my RX. Coming back West, 16-19. Factor that in with other valid points in the thread such as road surface, etc.

Johnhav430

Yeah I drove a Sienna to Toronto from Phila., and I was surprised, it got 29 mpg. I said to myself man this 4-banger gets decent mpgs, come to find it was a v6.

Stupidly, my wife and I switched at the border, AND FORGOT TO FILL UP IN NYS. Boy in my entire life, that has never happened.

Again, imho it all goes back to understanding how mpgs are calculated, which all kidding aside is not rocket science, if the same commute for 51 weeks yields 21.7, and week 52 it yielded 27, something was different that week. Oh and with that Sienna, which was brand new and I had to fix the third row myself (rental car), on the way back I refused to buy any fuel in Canada, and so the range was declining from 20, to 16, to 9, until there was none left, my wife was a bit uneasy but I told her don't worry, the car cannot predict the future (all highway). I have to admit seeing 9 was not a great feeling, though...

Aron9000

To the OP, did you actually do the math to calculate your MPG. You know, write down the odometer reading when you fill up, then write it down the next time you fill up, subtract the first mileage reading from second mileage reading, then divide that number of miles driven by the amount of gas you purchased?

I've found that on a couple of cars I've owned/driven that calculate the mileage for you, they aren't 100% correct.

mmarshall

In most cases, the computers are accurate to around 1 MPG or so.....usually not more than that.

Johnhav430

I've found my BMW to be accurate to .1-.3 mpg, using the odometer and the gas pump as references. This is why I really was clueless when my buddy said his Lincoln was way off, by more than 1-2 mpg. The LS430 seems to be accurate to about .3 to .5 mpg. Some variation may be introduced by using a different pump and where it stops, I have no control since I gas up in NJ which is full service. I think that as time progresses, these calculations will become even more mysterious. I was at Walmart the other day and what I was purchasing truly had no bar code. So the millennial clerk said do you know how much this is? I said, "five something." He enters $5.88. I say, "That's more than it is." His response, "It's close enough." Whose money is it anyway, right? It's been a really long time, but I thought there was something called a price check?

rxonmymind

Did it again. 25mpg. Simply by starting off slow from a stop has made a HUGE difference. I think I'm getting this drive easy idea. I still do 70 max on the freeway but from stop & go traffic just going EASY has made an impact. I'm impressed.
This is still with original everything. Before flaming me I have an appointment to change the spark plugs next weekend, maybe water pump, hoses & starter. None of which I'm certain will change the mpg but will ease my mind doing a preventive maintenance.

Aron9000

I wouldn't change the starter and hoses. My 1992 SC300, all the rubber bits under the hood are original in still in great shape. Toyota doesn't put cheap crap under the hood, those ones in your 2010 should be good to go. Besides I think its more about hot/cold cycles that wear out rubber bits, more than miles or age. Starter should be good to go, unless its been giving you problems, but generally that's one of those items that either works or doesn't work. Water pump, I'd leave it alone as well unless its leaking. MAYBE do it if you are due for a coolant change.

rxonmymind

Thanks for the advice. I'll keep that in mind.