40 mpg...

GOOD POINT!

It would useful to see how accurate your speedometer/odometer are relative to GPS or highway mile markers..

Bob Wilson

 

Justin, if the dealer foreman can get your average reading up to 47 when he drives it, then when you drive it goes down, your driving style is the likely culprit. You've stated you're not really trying to get good mileage. 2/3 highway but your average speed is only 18 mph? Sounds like stop than go. Driving smoothly, not darting in and out of lanes on the highway, maintaining speed, anticipating when you need to slow down will all help get your mpg average up. In warmer weather, the a/c can affect your mileage, especially when you're stopped in traffic or waiting for a ride because it will use the battery, which then has to be charged up by the ICE. My 2010 Prius IV averaged over 50 all the time, and my Prius v5 averaged over 40 all the time. Now I'm in a VW Passat TDI and get about 42 avg mpg.

 

You could run a set of benchmarks this weekend:

Did you ever try to replicate these benchmark data?

• drive 15 minutes to warm-up car, transmission, and tires
• find a level highway that you can set the cruise control for 10 miles
  • ideally do a loop
  • alternatively, do two passes, opposite direction
• record MPG after reaching cruise control speed for a distance of at least 10 miles
  • if doing two passes, reset trip-meter after setting cruise control and average results

We need one benchmark at or below 40 mph when the car is in 'hybrid' mode. Minimize the electrical loads including AC. Use the windows.

We need a second benchmark at or above 45 mph when the car is in highway mode. Same as above, avoid extra loads on the car, use the windows.

Speed is set and managed by using cruise control.

Bob Wilson

 

he's wrong about the 12 volt, and why don't you ride with him again and have him show you how he gets 47? a/c can knock it down a mile or two.

 

If you're doing a lot of stop and go traffic, where you have to do a complete stop, followed by having to accelerate hard, then stopping again a block later, that really saps mpg. But if you hit a string of green lights, then that helps a ton and that's how a lot of folks get high numbers in their prius while doing "city driving". The less momentum you have to lose, the better your mpg will be in the city.

Like others have said, check the battery as well. Preferably over the span of several days or a week, just to see what kind of readings you're getting, both before you start it up for the day, and at the end of the day. If it's consistently low, you may want to consider replacing it, as it'll give you even more headaches down the road especially if you have to let it sit for a period of time without driving it.

If you can find out, see how long the prius was sitting on the dealer's lot before you bought it. The longer it was sitting around, the more likely the 12v battery suffered. There have been posts where people said the dealer had to jump start the prius battery before they could even take it out for a test drive since it sat for so long. I think someone mentioned their 12v battery dying after leaving it sitting in an airport parking lot for nearly a month.

Other things to consider may be that we're still on the winter blend fuel, which gets worse mpg. Weather also plays a huge factor. Though it affects all cars, it's much more noticeable in the prius as a 10% drop from 50 to 45 mpg is much more dramatic than dropping from 22 to 20 mpg in a gas car.

And if you haven't already, watch this video. Preferably a few times:

 

Careful what you ask for: Preliminary 2010 mph vs MPG | PriusChat

The format of tables changed and I took this opportunity to put them in the new style.

Now I propose you run a set of benchmarks, one above 45 mph and one below 40 mph. Then vary one variable before repeating:

• AC off vs AC MAX and coldest setting - crack window if too cold
• bad 12V battery vs good 12V battery - expect to buy your own replacement as there are more affordable alternatives

I don't mean the full sweep of speeds. Just one below 40 mph when the car runs in hybrid mode where the engine goes off when it can. Another above 45 mph when the car runs the engine all the time. Then we can compare your data points to mine and begin to understand what is going on by taking out the 'human element.' We want to test the car, not the driver or route.
That is why it is so important to have a baseline, a valid, trusted set of benchmarks. Comparing yours to mine, we can gain insights to find out if there may be a problem with your car. The key is constant speed managed by the cruise control after the car warms up, ~15-20 minutes. Then make single changes and retest to measure the effect. There could be something yet wrong with your used car but diagnosis becomes a little tricky unless you have something to compare it to.

I am curious about your 'skill set' and car technology. Do you have a VOM? An existing OBD scanner? A personal tire gauge? Other technical experience with things mechanical? The reason is I want to talk 'with you' and understanding your comfort level. Knowing your background makes it easier when asking for data.

Thanks,
Bob Wilson

 

this caught my eye too. this can't be right. 100% hwy should be about 60 mph, 100% city/suburban is about 20 mph. OP, are you sure you actually turn the car off between driving?

now, my wife actually gets 40mpg when she drives the prius, but she drives aggressively; 80mph, hard acceleration and braking. she even managed to overheat the HV battery once. i tried to reason, but it's not worth the divorce.

 

Excellent!

A Volt Ohm Meter (VOM) measures electrical voltage, current, and resistance. If there is a Harbor Freight near by, they often have a nice 7-function unit for $5-8. The best thing is it lets you read the 12V battery and do other useful tests around the crib. <grins>

We'll make sure you get enough technical details to master the machine.

Bob Wilson

 

what is the voltage reading? unfortunately, many new 12 volt batteries need to be charged before installing. otherwise, your car has to burn petrol to try to charge it, which it does a very poor job of. it's really designed to maintain a good charge.
but i must agree with you, you're probably driving it for 40 mpg results.

 

1. Overinflated tires should increase mpg, even if just a little bit (1-2 mpg increase.)
2. Just because the car starts doesn't mean the 12V is "fine." It needs to be tested.
3. Running the A/C will have an negative impact on mpg. Again, not much.
4. Find a new dealer/service department.

 

If that's you in the Avatar picture......yea I can tell that you have a heavy foot.
Doesn't EVERYBODY in LA ???

 

Here's my thoughts:
-- There seems to be a disconnect between the 2/3rds highway claim and the 18 mph average. Just because you're on a "highway" doesn't mean you're driving highway speeds 2/3rds of the time, especially in LA.
-- The amount my CONS display differs from actual mpg varies greatly, so the CONS display is not a very reliable indicator of mpg.
-- I can easily increase the CONS mpg by simply driving at or below 20 mph in EV mode. I can consistently get 60-70+ mpg coming home from the gas station because there is a 1/2 mile stretch with speed humps before I get home and I'm usually in EV mode that entire stretch and then the block to my home.
-- If you force the car to use ECO mode, does it ever use EV mode? I ask because I don't know what happens when you press the ECO button. I use "normal" mode almost exclusively and let the car determine the most effective mode.
-- I know you said "moderate" acceleration, but I get the feeling it may be a bit harder than that and I'm not sure what using ECO mode does. I know you have to press further to get the same amount of acceleration. A better indicator of acceleration is whether or not the indicator is in the red PWR zone and for how long.
-- Turn ECO off and go for a 3-5 mile drive with the engine cold, even if it's just around the neighborhood. When you turn the car off, the display shows data for that trip only. It doesn't remain displayed long, so note the data as soon as you turn the car off.
-- Then go for the same drive with the car warmed up and record the data.
-- Then do that for longer drives with different traffic patterns, etc., and record the data.

My mpg is all over the chart. I have over 17,000 miles since July with over 50% of that at average speeds of 60+ mph and my average actual mpg is 45.7, with a low of 34.8 (68 mph) and high of 54.7 (42 mph). I could go into a lot of the variables, like cold weather, rain, headwinds, etc., but the point is to take the time to record the data and see what it shows. I can drive for 30 miles without my CONS changing, so I'm not sure what that shows. I can also take off and see the displayed CONS mpg drop from 50+ to the low 40s very quickly, especially if the car has had time to cool off or the heater is on.

 

I think the most important thing you've said is that you are in Los Angeles. I've talked to a lot of people whose MPG is normally between 40-42 MPG. Join the club. You wanted to do some of the tests on the 110. Maybe 10-15 years ago you could do that. Not now. If you want to do some testing, here's what I would do:

Go to the 210 after midnight, somewhere just east of where the 605 meets the 210. Set your cruise control to 60MPH, THEN reset your trip meter and drive to the 15 (or further) and back again. Yes, both ways. It's slightly uphill going east (into the San Gabriel mountains). If traffic is such that you have to take your car out of cruise control, then wait an hour and start again. Try not to change lanes very often. Your MPG should be in the high 50s and maybe up to 60. If not, then something is wrong. That's about as controlled of a test that I can think of doing in Los Angeles. I think it's too hard to do any kind of test doing city driving.

One other thought: What viscosity of oil are you using? Somebody once said here that if it's 5W-30, or higher, you could be losing some MPG. It should be 0W-20.

Mike

 

Using B mode will be hurting mileage. My advice would be to use it when descending hills with more than 600 Feet of continuous vertical drop, say Cajon Summit on I 15.