tmf2004

iTrader: (15)

For the past week or so i've been monitoring by distance to empty and miles driven and its just not adding up... For example just now i left the house with 400 miles to empty drove 12 miles round trip and now reads 368 till empty... This can't be right... I filled up last week (thursday) with 483 miles till empty on a full tank... Trip B says i've driven a total of 58.8 miles with 368 miles left to the tank..

AVG miles per gallon says 16.8 with normal driving...Its never been that low.. Usually stays around 24 for city driving.. Could i have some bad gas or a bad sensor?

Not getting any help on the Optima forums plus there's more knowledge here..

Thanks in advance..

SteVTEC

Well it's probably partially due to the colder weather, which I know is hitting Florida too. Colder air is denser, which means more drag. It also means longer warm-up times. In colder temps and a cold start, if you only do a two 6 mile trips, the engine oil temperature is probably never getting up to full operating temps, which usually takes 10-15 minutes (ignore the coolant temp gauge).

DaveGS4

iTrader: (2)

Likely colder weather and winter blend fuel.

Make sure to check the usual suspects on your car like tire pressure and a clean air filter.

tmf2004

iTrader: (15)

Today is in the 40's but i noticed this over the weekend driving to work.. I only work down the road.. .thanks for the replies..

Edit... can the parts store run a diagnostic and see if any sensors are bad?

Sulu

The distance to empty number is calculated and forecast based upon past average fuel consumption. If your fuel consumption on your most recent trip was particularly high, it will have a negative effect on your distance to empty number -- it will forecast to be (much) lower than you would believe it should be based upon the pre-trip forecast and distance travelled during the trip.

As we know (and suggested in other responses above), fuel consumption in cold weather and short trips is quite high. Fuel consumption is always quite high on a cold engine but decreases as the engine gets warmer, averaging out to a lower average fuel consumption as the trip gets longer. So if your most recent trip was short (and shorter than your past trips), the average fuel consumption for the trip will be higher than for a longer trip, and your distance-to-empty forecast will be lower than you would think it would be.

Lil4X

^^ What Sulu said. That "Miles to Empty" is at best and estimate, based on your most recent driving. It's a help, but not a guarantee you'll reach your destination before your engine sputters out. One thing seems to be pretty consistent for some reason is the "warning light" for low fuel.

Our minivans, daughter's truck, and our last two Lexus' have all reliably delivered about 32 miles before things got really dicey and you were judging remaining fuel by the percentage of the guage's needle beyond the "E" mark. That's across a range of vehicles ranging from new to 25 years old, producing anywhere from 15 to 26 mpg and fuel tanks holding somewhere near 18-20 gallons. I don't know if this is simply a matter of coincidence or there is some common threshold that automakers take as the "warning" level. It can't be that accurate, considering the differences in fuel measurement, plumbing, and performance.

SteVTEC

If it was something with a sensor you'd be getting a check engine light.

If the car is driving differently though, especially if it seems sluggish, might be worth it to get it checked out. Old Nissan Maximas would tend to chew through knock sensors. When they went, the ECU would retard the timing back all the way and there was a huge loss in power, and fuel mileage dropped like a rock also. But because it wasn't important for actual emissions performance there was no check engine light, although if you ran a code reader on it you'd still see a ghost code for the knock sensor.

So if it seems to be driving the same it's probably just the cold weather. But if it's driving a lot differently, get it checked for something stupid like the above.

tmf2004

iTrader: (15)

thanks guys.. car seems to be driving the same.. no hesitation or rough idle

bluestar

The Kias and Hyundais have a particularly bad DTE/MPG calculator compared to my other cars. With the Koreans, every stop light the car is idling takes away from your DTE/MPG... So much that it screws up your exact calculation based on actual miles driven. I have just learned to ignore the car's DTE read outs.

tmf2004

iTrader: (15)

guess i do to...

mmarshall

The earlier comments about cold temperatures and the resulting richer air-fuel mixtures and lower MPG are correct, but also keep in mind that the Miles-to-Empty function on the trip computer is often purposely set a little conservatively by the car's engineers for liability reasons. Look at it as just one more safety margin built into the system to (ultimately) help keep you from running out of gas in a remote area and doing this:

chikoo

I guess this post got to him

Hyundai America CEO John Krafcik Steps Down

j/k

tmf2004

iTrader: (15)

lol.......

chikoo

that post of yours cost him $395 million....

speedflex

Our cars (ES350, RX350) do this too. I really don't pay that figure any mind as it changes moment to moment based on driving habits. it's going to calculate a different DTE at 45mph versus 75mph.