Erratic Gas Mileage

- What fuel economy are you getting and how are you determining fuel economy? (Trip computer or manual calculations)

My problem is variations in the fuel economy and the power.

When things work well Highway at 60mph in ECO mode in warm weather 48 mpg. City – 50.

At other times , under the same conditions ( temperature, warm engine , no hills, ECO mode- some pulse and glide ) - Highway at 60mph in ECO mode in warm weather 41 mpg. City – 42.

I use pulse and glide, drive in ECO mode, avoid sudden acceleration. Brake well in advance of stops.

There seems to be no factor to explain this. Suddenly gas mileage will be very good. Yesterday it was good starting a cold ICE that had not been run in 2 days and yet suddenly the gas mileage is great. No the problem is not the trip computer –I’ve checked it against the manual method and it never varies more than 2 to 5 % and it always read high by that amount. I can tell be the car itself as the ICE seems to lack power when the mileage is poor- I have to press the pedal harder.. Even the slightest grade requires pressing gas hard enough to make the ECO light go off. It is not possible to use pulse and glide when it is in this bad gas mileage mode.

The good/bad mileage difference is very noticeable and seems to start with turning the car on and lasts until it is turned off. Kind of a Jeckle and Hide personality – different each time you turn the key. It has been this way since I bought it – one-year-old demonstrator from a Toyota Dealer.

- What fuel economy are you expecting and why?

Constant fuel mileage used same conditions maybe 46 highway and 48 city under good conditions.

- What are the approximate outside air temps?

I only complaining about temperatures of 65 to 80 F without AC or auto temp. I understand the lower mileage outside those ranges.

- How long are your trips?

Both the good and the bad mileage occur on trips of the same length – whether it is 10 to 100 miles.

Both the best mileage and the worst mileage occur on trips of 10 miles.

How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? I tested it with the method ( cold with headlights on for 2 minutes ) 12.4volts

Have you had your alignment checked? Any pulling or abnormal tire wear?

I will take it in for an alignment soon – but the problem has occurred since I own the car and my tires wear evenly. I have 66,000 miles on the car.

- How much of it is city vs. highway? Roughly, what's the average speed in overall and of each segment? Is there a lot of stop and go driving?

In the city I drive it around 30 to 40 mph. Yes stop and start every ½ mile – but I get my best mileage there and my worst ( in cold weather).

- What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.)

Flat.

- What are your tire pressures?

34 -35PSI – 1 to 2 pds over spec.

- Is your oil overfilled? (i.e. above the full mark on the dipstick)

Oil is never over filled . I buy and put in 0W20 Mobil 1 at oil changes.

- Make, model, year, engine and transmission of previous car? (e.g. 08 Honda Civic Si 2.0L 4 cylinder, manual transmission) What did you actually get on the same trips/commute? (Please give us actual numbers, not EPA ratings.)

2000 Honda Accord – 2.3L engine automatic. I got 33 – 35 mpg Highway, 28 city.

- What region/state are you in? (if you haven't set your location)

I’m in Canada – car is US - – Ottawa but the weather I’m measuring is 65-80F.

- How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking?

I brake in advance gently enough to regenerate max. power on the gauge. Anytime I press EV mode a message appears saying “not possible – excessive speed” even if I’m doing over 20mph. I no longer try to use EV mode – the car simply is too weak in EV mode to run.

- What modes are you using, if any? "normal", EV, power, eco?

I use ECO exclusively except for gentle acceleration. When the car starts in the bad mode (lower mileage) it requires pressing harder on the pedal and leaving ECO mode – using PWR mode for even modest acceleration.

- Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on? No

- Are you driving using D or B mode? D

- HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to?

The gas mileage I’m quoting is with AC off and Auto OFF . Heat off Fan only.

- Are you using the factory tires and wheels? If not, please indicate tire make, model and size (e.g Asurance Fuel Max 185/65R15).

My model came with, And I have replaced with same Michelin MXM4 with GreenX for lower rolling.

Tire pressure 1 to 2 pds over spec, air filter is clean, ICE runs very smoothly.

- If reporting a mileage drop, did anything significant change on your car (e.g. accident, hit a curb or big pothole throwing off alignment, oil change/other maintenance/repairs, changed tires or wheels, etc.) or your commute?

There was a software recall I had then do shorty l after I bought the car, It might have made it slightly worse. My suspicion is some sort of problem in the electronics.

 

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Some days with a trip of 5 miles , there is little power and I can't seem to get the electric to kick in, other times it does kick in even under the same temperature and distance conditions.( by kick in I mean depress/repress gas pedal and the gas mpg bar goes up .) Other days it takes 20 miles before the Electric can kick in. Strangely it seems as though the "good gas mileage" lasts several days and then it switches to bad gas mileage due to being unable to engage the electric. Seems to be independant of the battery charge indicator.
I tried using cruise control - its gas mileage is much worse as the car has to roar on gas to make it up the slightest incline even at low speeds ( say 30mph).. I will look into the minVCI - any ideas where I can buy one? Dave

 

I typically manage about 42 mpg on a tank ( I typically fillup around 300 miles and that takes about 8 gallons).and that's being very carefull with acceleration and coasting. It's actually better on the short trips , even if they are only 5 miles. There just isn't much power on the highway -and believe me I am driving like a 90 year old lady.

 

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