Are people really getting 40+ MPG in Gen 2?

are the sumo's low rolling resistance?

 

fair enough. let's see how it all shakes out, after you do your maintenance.nothing you've listed should affect mpg's. i would buy a meter for the 12v, clean the throttle body/maf, intake manifold, egr valve, pcv and etc.

 

Yes. While the miles travelled number resets after you get gasoline, the MPG number should stay constant until you hit the reset button. The MPG number is averaged across all the time since it was last reset, even though the car won't show how long that's been.

 

Only two things jump out at me, and both too small to cover this MPG case:

I don't see any Sumitomo tire models in the tire list thread:
Low Rolling Resistance replacement tires: Current List | PriusChat

Non-LRR tires will provide a small but permanent MPG cost, generally not enough to be worth changing out good tires. Additionally, new tires seem to temporarily produce lower MPG until they break in.

Auto mode is known to be a bit of an energy hog, though again, not by enough to account for your shortfall.

Consider turning the AC away from of Auto to a fixed low-to-mid fan speed, raise the temperature number as much as you comfortably can (i.e. don't spend fuel on over-cooling), and possibly direct all the dash vents at you (close the far away passenger vent) so that you are not trying to cool the entire car's cabin when there are no other passengers. But when you live in climate that demands AC (my climate zone usually does not), then this is just one of the costs you have to pay buck up and accept.

And one more thing -- Don't take the shop check as gospel, many others have been told the same thing on weak 12V batteries. Please go through the actual check procedure, on a battery that has been resting (car off, ignition never READY for a number of hours), and report the voltages back here.

 

timmyjane, that is the correct behaviour on the 2004-2005 Gen II. There was a change to the behaviour in the 2006-2009 Gen II to that noted by Moving Right Along.

I disagree in this particular case, with the OAT at 80ºF and the climate set to 73-74ºF, and once the car is fully warmed up, there will be fairly limited draw that would cause lower MPGs.

 

IMO, a well maintained Prius, in good adjustment, with no major issues, SHOULD be doing a whole lot better than 34 mpg.

Even one that is over a decade old, with 230,000 miles on it.

 

One more common item that isn't covered on Cwerdna's questionnaire: brake drag. Corrosion can cause disk brake calipers and pins to not properly slide, causing some pads to drag on the disk when the brakes are not supposed to be engaged. This is usually asymmetric, only one or some pads are dragging. Gen2 rear brakes (in North America, not elsewhere) are drums, not disks, they may have a separate issue.

This can be detected by feeling the hubs after driving, and stopping gently with as little friction braking as practical. (Regen braking is ok). If working correctly, the brakes and hubs should not be very warm. If you get burned, then they are dragging a lot.

When jacked up with wheels off the ground, rear wheels should spin somewhat freely, you can easily feel any brake drag. Front wheels are tied to the propulsion system, so this test doesn't work there.

I've had this on two past cars, not my Prii. Western Washington's newfound love of winter salt seemed to be a factor in the more severe case.

 

Serious drag is detectable this way, I can't speak for minor drag. For feel and MPG loss, it doesn't matter if it is the service brake or the parking brake, same issues.

I can't speak to your other questions, those are out of my experience base. My household has taken three vehicles to the 200,000 mile bracket without needing any of those services. The two that are no longer with us, were getting the best MPG of their lifetime right at the end of our ownership of them, though that was more related to better adjustment of the 'nut behind the wheel' than to any mechanical tuning.

 

My 2005 Prius currently has 300,000 km. It has pretty much consistently gotten around 50 to 56 MPG since the day one (when I bought it S/H at 58,000 km).

So far my engine performance is still good, and to be honest it's efficiency doesn't seem to have changed very much over the years. The HV battery performance has gradually declined though, and under some circumstances this can reduce the MPG a bit.

Under sedate driving conditions a moderate loss of HV battery capacity actually has surprisingly little (near zero) impact on MPG. Under more demanding conditions however, particularly when it's driven hard enough to make it swing "purple to green" and so on, then an aging battery does reduce the MPG somewhat.

 

You can't judge a Gen 2's mileage by the tank. It has a rubber bladder and the tank size varies by the weather (colder weather smaller bladder). Only way to judge mileage is fill the tank, reset trip odd to 0, drive then when it's time to fill again. divide miles driven by gallons used, Repeat at least 4 times, then you will have an idea of your mileage.

 

... in North America. Note that several respondents here are in other countries that have true rigid tanks, not that cursed bladder.

 

Overall for past 3 years ~40 mpg, last fill-up 49.9mpg (!); 2009 Gen II with just over 119,000 miles on odometer. Tyre pressures 48F/46R. ...er, that's it!