Same Prius, Not The Same MPG

[Dark_Prius]

I have been having problems with my prius' MPG, no matter how hard I tired I get about 38MPG~43MPG. Following all the tricks from PC.

Today, I had a chance to preform a test with my sister's prius, same package as mine with the following specs:

2010 White Gen 3 pkg 3, 1300miles, ave 38MPG ~43MPG.
2010 Silver Gen 3 pkg 3, 1150 miles, ave 48MPG

First, I took my car for a 20 miles drive mixed with city and freeway, not much traffice, AC at 68 degree. I got 44.6mpg from my white prius.

Next, I took my sister's car for the same drive, same AC adjustment and I got 51.2mpg.

Her prius seems to be able to glide much better than mine. When I was on the freeway, her Silver prius can maintain 65 to 70mph with 50mpg. As for my white prius, when I try to maintain 65 to 70mph, my mpg meter reads below 40mpg.

My white prius seems to have more drag and kills my mpg. I really think there is a quality problem with my prius but not bad enough to have any warming lights.

I will try to take it to the dealer and see if they are willing to help.

Does anyone of you out there experience the same problem?

Please advise. Thanks,

[bwilson4web]

Start with:

• what are tire pressures?
• what are engine oil levels?
• was fuel - same brand, 87 octane?
• was cruise control speed used?
• wheel alignment? (requires a fee)
• weather effects - temperature, wind?

Your indicated MPG suggests speeds above 70 mph, closer to 75-80 mph. At these speeds, small changes can make significant changes in the indicated MPG.

Bob Wilson

[fuzzy1]

And to verify the obvious --
Parking brake fully released?
Brakes not dragging excessively? (compare brake disc temperatures)

[Dark_Prius]

My white prius with low MPG got higher tire pressure 42/40 vs 35/33. Not the tire pressure for sure.

Both prius are still using the oil that came with the car.

87 octane, no cruise control, same driver, weather is the same. As for wheel alignment, both car drives the same.

I am going to check the brakes, the white prius seem to have more drag. I feel that I need to work on the gas paddle harder. it doesn't run as smooth.

Definiately something is wrong internally.

[Shawn Clark]

Originally Posted by Dark_Prius

My white prius with low MPG got higher tire pressure 42/40 vs 35/33. Not the tire pressure for sure.

Good, one item checked off.

Both prius are still using the oil that came with the car.

That's not the question. What is the oil level on the dipstick in each? What you've said is effectively, "I don't know."

87 octane, no cruise control, same driver, weather is the same.

If they aren't from the same station then you have a difference. 87 octane can be very different from one place to another.

As for wheel alignment, both car drives the same.

Doesn't mean anything. They don't drive the same because yours doesn't glide well. Have the alignment checked (you get a free one in the first year.)

Definiately something is wrong internally.

Not at all definite. Possible, especially with such a large difference, but far from definite this early. See the above for a sampling.

[Dark_Prius]

The white prius with low MPG oil level is correct, in between the low and top marks. I didn't check the silver prius, since it got the high MPG.

I doubt getting gas from different station will make any different in MPG.

The prius only have front alignment, there is no alignment at the rear. For the front alignment, only camber is adjustable. If the car drives straight, there isn't much they can do.

One thing I got really piss at the dealer is that I took my car in last week asking them to check for my alignment. I waited 4 hours, and all they did was rotated my tires and put 30miles on my car as test drive. They didn't even put my car on the alignment rack.

I made a complain to Toyota, if they cannot fix my prius. This will be the last Toyota I would purchase for the rest of my life.

[DaveinOlyWA]

drove both in same mode?? not a lot of difference between ECO or PWR but if doing a lot of small grade changes, i think it will affect your mileage.

i suspect oil level overfill and alignment.

[bwilson4web]

Originally Posted by Dark_Prius

. . .

I am going to check the brakes, the white prius seem to have more drag. . . .

Definiately something is wrong internally.

Alignment can be off and the handling won't seem different. As a suggestion, if you have one of those non-contact IR temperature readers, you might take a drive and then scan for 'hot spots.' A brake would be easy to detect but it could also show up as uneven tire heat.

Sounds like an interesting puzzle. Please share whatever is found.

Thanks,
Bob Wilson

[fuzzy1]

I mentioned dragging brakes due to first hand experience. When I had this problem on a long-ago domestic, caused by a shop who claimed it was normal up until the moment the wheels began smoking, a thermometer was unnecessary. The IR radiating off the discs could be felt several inches away, and the hubs were very noticeably warm to the touch. The discs themselves were too hot to touch for even an instant.

[morpheusx]

next time drive the exact same route, by taking it on the highway and set the cruise at the exact same speed (there is less variation for time of day with highway driving). I haven't driven the gen. III yet, but I can tell you that there are times when I can make my 25 mile trip to work at 75 MPG and other times I am struggling to make 52 MPG based on variations such as the ones mentioned above or current traffic patterns. (same car with no changes)
In your case I am still betting on it being either Climate control use (there can be a large difference in usage just from it being sunny or cloudy), tire pressure, or type of gas. If they rotated your tires they most likely lowered your TP be sure to check only after the tires haven't been driven on in at least 3 hours.