2006 Sonata GL MPG

Things are definitely looking up in the mileage department with the
warmer weather. I just got my second tankful of 31+ MPG. I got exactly
31 today and my last tank was 31.02. It looks like the change to
synthetic oil cost me 0.02 MPG. I couldn't resist....

With these last two tanks, my mileage average since buying the car (it
now has 5500 miles) has crept above 28 MPG. I'll be a happy camper if
the average stays above 30 for my daily commute. That should mean that
the EPA 34 highway rating is actually achievable on a long trip.


Matt

 

I getting MPG gains as the weather warms as well-haven't hit 30 yet though.

 

What engine/transmission combination do you have?

Matt

 

v6 auto (LX)

 

Hitting 30 consistently with your LX would be very impressive as, if I
recall correctly, that is the EPA highway rating. You wouldn't expect
that unless you were on a long trip. If you are even getting close to
30 in daily driving, I'd say you are doing well.


Matt

 

I think I know why my mileage took such a step change from 27 to 31 in
the last two tankfuls. I was thinking it must just be the warmer
weather and the car getting broken in more, but I no longer think that
is the case.

A friend at work was telling me that his Civic HX (I think I got that
right) gets 46 MPG during the summer, but only 40-42 during the winter.
He said it changes when they switch the gasoline from summer blend to
winter blend. I hadn't even thought about that, but I'm betting that is
what also affected my Sonata.

Have others who live in northern climes that use different fuel for
winter vs. summer seen this same behavior? My minivans don't seem to be
affected as dramatically, nor my pickup. That would certainly explain
the rapid change. I was trying to figure out how a slow warm-up in the
spring could have such a rapid change on the mileage. It didn't make
any sense, but changing fuel blend does make sense.


Matt

 

My last tankful achieved 31.6 (nearly 500 miles on one tank!) so things
are still improving slowly. Hey, this car may bet 34 MPG before the
summer is over!

Anyone run theirs dry yet to see if the tank capacity is really as
advertised? I haven't run more than about 15 miles after the light came
on, but have yet to put in more than 15.6 gallons, which means I should
still have a couple left.


Matt

 

I haven't run mine dry, but I've wondered the same. The most I've ever
put in is 15.6 gallons as well and it's usually closer to 15. I've got
the GLS with the trip computer and the light usually comes on with
somewhere between 45-60 miles to go on the Range. Based on the 27.5 MPG
that I've been averaging, that's another 1.5 - 2 gallons or
so...assuming the computer is accurate.

Doing some rough math, that seems to be a little less than the 18 gal.
capacity. I'd prefer not to find out the exact amount the hard way,
though.

Barry

 

In the past, I've run some vehicles dry on purpose (with a can of gas
along) and one by accident. The latter my current Chevy truck which
I've twice confirmed holds about two gallons less than the amount stated
in the manual. The first time it ran dry, I was literally able to coast
into a gas station ... talk about dumb luck. I was only able to put in
something like 24 gallons, and I believe the book capacity is 26 (I
haven't checked in a while so this is purely memory). In any event, it
took two gallons less than specified. So, I carried gas along next
time, which was easy as I had a 50 gallon tank and pump I used to refuel
my airplane and ran it dry on purpose. Same result, it took two full
gallons less than advertised. This is good information to know in a
pinch. Also, the truck has a very nonlinear fuel gage. It takes about
90 miles to get the needle down to the full mark after a fill-up. The
needle goes about a quarter tank above the full mark when full. It then
takes about 180 miles to get to the half-tank mark. And then about 130
more and you are out. Once below the quarter tank mark, the gauge drops
like a rock.


Matt

 

Running an electric fuel pump dry is really hard on it. Even sitting still
with not alot of gas in the tank is a bad thing to do. They are cooled by
the gasoline. While the car is in motion, whatever gas is left in the tank
is sloshed over the pump and helps cool it. While running the car out of gas
once is not likely to kill the pump, it really doesn't help with it's
longivity.

 

I've heard both sides of this and am pretty sure this is another urban
legend. A fuel pump designer in another ng (I believe the Chrysler
group) said that the fuel pump is cooled by the fuel going THROUGH it,
not sloshing around. If the fuel pump is still pumping fuel, then there
is no danger of overheating it. And once the tank runs dry, most folks
turn off the key before the fuel pump runs long enough to damage the
pump. Personally, I don't know for sure, but I've run my cars nearly to
empty for 20 years and have had only one fuel pump failure and that was
after 150,000 miles, which is considered to be decent life for an in
tank fuel pump.


Matt

 

Call it urban legend or whatever you want.

I knew of a guy that owned a garage in Rapid City, SD. Every Summer, he
made sure that he had access to fuel pumps 24-7, because people were always
coming in off the mountains, stopping for gas or whatever in Rapid City,
then be unable to start their cars again, because of fuel pump failure.

In almost every case, there was mountain driving in the heat of Summer, and
the consumers confessed to usually driving their fuel tanks down "further
than they should have more than they should have."

Bottom line - since it is at least possible that this happens, and since it
makes little sense to run your fuel down that far anyway, just don't do it.
Fuel pumps are an expensive job, unless you are one of the lucky ones that
has an access port to it in a trunk or a back seat - otherwise, it is drain
and drop the fuel tank and go from there.

Tom Wenndt

 

That's an even better legend! We're supposed to believe that all of the
fuel pumps magically failed in Rapid City only when they stopped for
gas? They didn't fail 10 miles before the City or 10 miles after? I
guess the question I have is what were the gas station folks doing to
kill the fuel pumps so that this garage could fix them and how much of a
kickback was he giving to the gas stations. They had scams like this a
few years ago on 20/20 or one of those similar shows.

Sorry, but I'll believe a fuel pump designer before I'll believe a
mythical garage owner in Rapid City, but that's just me...

Show me one warning in an owner's manual or shop manual about not
running your tank low to prevent fuel pump failure. Just one...

It's possible that the sun won't come up tomorrow also, but I don't
worry too much about that. There are enough probable things to
worry about that I don't need to worry about the improbable ones.

I don't see why it makes sense to stop and waste time buying gas more
often than one needs to. Once I know that I need gas, I stop and fuel
up, but I don't see any reason to stop every half tank when I can run
down until the light comes on or nearly so and have 100% assurance of
getting to the station, since I know where all of them are on my daily
commute. I agree that if you are traveling and not sure where the next
station is, then stopping the 1/4 tank point or so makes a lot of sense.

Matt

 

Hyundaitech,

What is your take on this? Do they warn you about this at Hyundai tech
school? Do you see frequent fuel pump failures on Hyundais that might
be attributable to running low on fuel often?


Matt

 

I think I would have to call that urban legend Tom. Either that or bad
data. It's just wildly inconsistent with the experiences of literally tens
of thousands of vehicles driven in virtually the same conditions every day.
I suspect the fellow you know of was overstating a case.

 

I'm talking from experience on Chevy 3500 Vans. I worked for an electric
utility, and many of the vans idled for hours to provide AC power for
certain test equipment. We had a rash of fuel pump failures - mine included.
We were cautioned not to idle them if the tank was less than 1/4 full
because that would leave the motor of the fuel pump out of fuel - the intake
was still well under the fuel level. I know my Town and Country passes fuel
over the motor when it's pumping - http://tinyurl.com/h62yw - so what was
said about the fuel pump designer is definitely true about Chrysler. The
Chevy pump motor is out in the "open" in the tank. It is only cooled by fuel
around the outside of it. I don't know if that's the case with the Hyundai
pump. There's also baffles in the Chevy tank that help with the level. From
what I saw, driving the vehicle with a low tank didn't seem to kill them. It
was when the vehicle sat still even when the tank wasn't terribly low.

It's not entirely urban legend.

Also, once an engine stalls due to lack of fuel the pump shuts off after a
few seconds. It's not controlled by a pressure sensor. It's controlled by
pulses from the ignition system. Cranking the engine starts the pump for a
few seconds, and it stops a few seconds after you let go of the key. You'll
not likely cook a pump in the short term - especially with no back pressure.