Omarus

Hello!

I have a 2006 model. When I first got it around a year ago it did around 22MPG but it kept on getting worse over time and now it average 19-20MPG on mixed but mostly city driving.

Here are some details:

- I did the ISC reset, twice, no difference.
- Michelin tires at 35 PSC.
- Warm weather averaging 85F, A/C always on.
- I am familiar with hybrid driving techniques and try to use them all the time. This average is with those techniques being used.
- Maintenance has been done twice at the dealership
- One thing I noticed as off, the car does not charge often when I press the brake. Many times the charging indictor barely touches the blue section even when the hybrid battery is full. At times it does this (dipping heavily into blue charging territory) but mostly it doesn't.


Any ideas on what could be wrong or what can I try ?

Thanks in advance

maseace

- Are you mainly driving on very short trips (less than 5 miles)? You won't get decent mpg until the coolant temp is over 157°F, then the engine will shut off when coasting/braking.
- Is it very hilly where you drive?
- Are your tires low rolling resistance? (Michelin Green-X) Try 40 PSI.
- Check the energy monitor when coasting or braking - it should have arrows flowing from the wheels into the motor-generator, to the battery. Like in this photo.
- Is your air filter clean/replaced regularly?
- Is the vehicle properly maintained? Do you have any check engine light codes?
- What octane fuel do you use?
- What speed are you driving? I have noticed much worse mpg at 70 mph vs 55 mph. Also keep it below 42 mph to allow for "warp stealth" mode in city driving when possible.
- Get a Scan Gauge or Ultragauge to see the RPM, coolant temp, and other data using the OBD port.

borscht

Here is what my observations have been. Of course, I only had my 400h for 4 days so take this with a grain of salt.

1. On very short trips, no matter if the engine is warm or cold, I get 15 mpg average. This is get out of the neighborhood, go to the supermarket, take my daughter to school and back.

2. During acceleration from stopped, the "instant" consumption is 7-8 mpg, unless you barely press the pedal to get electric only, which isn't really safe on the roads with other cars.

3. My best "instant" consumption (not counting the 99mpg coasting) is when driving down a city road at about 40 mph.

4. My battery mostly stays at about 80%, blue bars. Yesterday after coasting down a long hill I saw it turn 90%, green bars.

5. I have only seen it go below 50% once, and that was before I did a reset.

6. I did do a reset with the gas/brake pedal thing.

7. This morning, on the way to work, which is 15 miles, about 10 traffic lights (1/2 of them red), I got an average of 27 mpg. I was thrilled. The last leg of the jorney, about 1/2 mile, there were no cars behind me so I cruised on electric only all the way into the parking lot. I was pleased.

Omarus

Thank you for writing all these questions. Here are my answers

- No, there are hills, but its not very hilly
- Tires are low resistance
- The charging (green arrows) occurs when coasting or braking from the two motors to the batter
- The air filter has been replaced around 6 months ago at the dealership
- The vehicle is properly maintained, I have had it around close to 1.5 years and its been to the dealership twice (regular maintenance light).
- I use 92 octane, in my country this is actually the lower grade fuel, the better one is 95.
- I would say my average speed in the city is close to 40-50 MPH

I hope these answers help you "debug" what is wrong with my car's milage.

This really bugs me, I am ashamed to share my 20 MPG number when people ask me, as this is really bad for hybrid territory

joedaddy1

iTrader: (1)

try a higher octane.. i believe 98 octane there is equal to 91/93 in the states..

how old is your 12v battery.. this sounds weird, but it seem to affect the 400h.. (don't quote me on this.. just personal opinion..)

also, what kind of oil are you using? these cars call for 0/5w-20/30 weights.. any thicker, it won't help you on the mileage department.

maseace

Good call on the 12V battery. If it's the original 2005/2006 battery, get a new one! (And do the ISC reset again) I have noticed better MPG with 0W-30 compared to 5W-20 oil.

joedaddy1

iTrader: (1)

hmmm... i would think the 20 weight would give a better mileage than the 30...
try a 0w-20 weight in the winter, since you are in WA..

maseace

I can't seem to find 0W-20 around here, and I'm not willing to get gouged at the dealer!

Edit: Found some Quaker State Q full synthetic 0W-20 at the local Walmart for $21 per 5-quart bottle.

riwyle

0W-20 might give you an additional 0.1-0.2 mpg at the most. I wouldn't be concerned about the oil.

rcy

The ISC reset is tricky to do on you own (though, it can be done). Might have to bite the bullet and ask the dealer to hook up to their computer and see if the ISC reset is complete. Other than that...all I can think of is the brakes maybe...sticking caliper, dragging pad, or parking brake not releasing properly.

glassmanj

it could still be your driving style also. if you accelerate quickly you'll always get bad mileage. use the mode button on the steering wheel and set it to show the battery level icon. when you're driving. don't hit the gas hard, use it very lightly and try to feather the gas so only the battery is sending energy to the wheels and teh engine icon doesn't appear. . on a flat surface you should be able to do at least 20mph just on battery and thus you are using no gas.

when you are driving on flat road doing between 30-50mph, as you are cruising, try to barely hit the gas where the battery sends power the wheels only and try not to push hard enough to kick the engine in. it's a game you have to play but it makes a huge difference. when a hybrid set the record for mpg, they used a pulse method where the theory is to accelerate as much as possible only using the battery before the engine comes on and coast until you do it again. the theory is on a 50mph road, you'd accelerate to 60, coast back down to 40, and still average 50. and you hopefully never use the gas engine.

when a stop if coming up in the distance, let off the gas as far as possible away from it and coast. don't keep using gas and then slam on brakes. 400h has low resistance so it will coast a long way. think ahead and don;t waste gas when you can coast. this is huge.

another reason is AC. are you using yours? it makes a huge difference in mpg. so does the heater. on a hot day, if you car has also sat in the sun and the dashboard is very hot, it takes a lot of energy to cool the car while the dashboard is radiating tons of heat. use a sunvisor or dash cover and the AC will work way less to get the car cooler faster.

also make sure you air pressure is what the tires are rated for and not what the car specs say. i recently had an oil change on another car at mobil one and the tires are rated 44psi. the techs said the original car tires were only 35psi. but my replacement tires are 44psi. they wanted to under inflate them which costs you mph. look at the rating on the tire and make sure they are set properly. don't assume someone knows what they are doing. they don't look at the small print on the tires when they fill them. they look at what a computer screen tells them.

just some thoughts, hope even one helps.

maseace

Yeah my 400h door plate specifies 30 PSI for the tires, which is WAY too low for best fuel economy, and that's what shops will go by. I keep them at 40 PSI. The max pressure on my tires is 51 PSI, so I could even go a lot higher.

By the way, the max pressure stamped on tires is NOT the burst pressure, so you are still safe to the max pressure. I saw an interview with an expert on Motorweek that the burst pressure is about double the max pressure.

takeshi74

Keep in mind that pressure increases as the tires heat up. It's certainly possible to overinflate and you'll notice it by the wear pattern.

MeryLexmas

I commute to Washington D.C from my house in Maryland. It is a 33 mile commute. I used to average about 28mpg. I switched to 0w-20 Mobile 1 and inflated my tires to 38psi cold. Using mild hyper-milling techniques I can now average 36.6mpg. Even driving with a heavy foot I still get about 425 miles per tank.I don't know how some of you are getting such crappy mileage. I've only had the RX for a couple weeks. It's a 2007. So far I love it!

Weighit

Don't reset that display for 4 or 5 tanks of fuel then take a photo of the overall mileage reading.