2006 Sonata GLS v6 Initial Quality Feedback

It was a Park Avenue that I rented to drive from Corning to Boston a few
years ago. I was driving 75-80 most of the way and that beast got 31
MPG. I thought it had to be a mistake, but the fill-up matched the
computer within a few tenths and I duplicated the performance almost
exactly on the way home a few days later. Amazing for a car that size
at that speed. I still almost don't believe it.


Matt

 

16-17??? Holy cow Matt - that's big time mileage. You must have the super
secret mileage booster package. My 1500 gets a steady 15mpg no matter how
you drive it. Local driving - 15mpg. Empty drive from Syracuse to Philly
(72mph in NY state, 80-90 once on the Northeast Extension) - 15mpg. Full of
my daughter's belongings bringing her back from college - 15mpg. This truck
only knows one stinkin' mileage rating - 15mpg. Unless of course I stick it
in 4WD. Plowing snow in 4Low and it's a steady 6mpg. I never use 4Hi for
long enough to know what that would be. Hell, I couldn't get 16-17mpg if I
coasted the truck down hill for half a tank of gas.

 

I have a 94 K1500 with the 4.3L V-6 and the wide ratio manual
transmission (I forget the designation, maybe MT8, but the one with the
granny low ratio). Mine pretty much is stuck on 16 like yours is on 15,
but I occasionally get 17 and occasionally 15 (mostly in winter). When
I plow I get 10-11.

I replaced the stock 3.73 ratio diffs with 4.56 ratio as the engine was
simply lugging too much at 55 MPH (only turned a little over 1600 RPM in
OD) and I actually got better mileage with the lower ratio and it starts
out a lot better and plows better.

I plow in 4-high and in L gear (the shifter isn't labeled 1-5 like the
close ratio 5 speed was (if memory serves), but rather L-1-2-3-OD. With
the 4.56 gears, even in high range the low gear is pretty low.

The best ever mileage was 19 MPG that my brother-in-law achieved on a
trip to Ohio to deliver his daughter to college. That was the only
really long highway trip the truck has ever had.

I have a fiberglass cap on the truck which cost me a little mileage and
I put a hood deflector on which cost me some more. I was getting closer
to 18 on average before adding these two items.

I generally drive 55 - 60 on the highway, but this truck sees 50%
highway at most. The weird thing is, as you say, it almost doesn't
matter how I drive the truck. I can run it hard and rev it high before
shifting, I can drive at 50 or 65, it still gets 16 MPG almost all the
time. Weird.


Matt

 

I have bought a new GLS V6 in December. Driven less than 2000 miles so
far.

I used to drive 1996 Camry before.

I am very happy with the new Sonata. Yet to find a problem with it.

Only disappointment is that it gives me about 20 mpg and I drive mostly
in the city with lots of traffic lights. I have noticed that mileage is
much better on highway, but I haven't recorded any numbers.

I can't compare the mileage with my old Camry because that was
4-cylinder with much less power.

Good luck with your decision.

 

My Silverado is a '94 with a 350. Has a fiberglass cap on it also.
High-rise style.

 

Makes you wonder if the carb is calibrated very lean. It makes the engine
run hot, but really helps mileage. The down side is that it could shorten
engine life a little.

 

Same here. I suspect the difference between my mileage and yours is the
V-8 vs. the V-6.


Matt

 

These cars haven't had carbs for probably two decades... Running
hotter, assuming good oil, will make an engine last longer in general.
Most engine damage occurs when the engine is cold, not hot, unless you
run it out of water and REALLY overheat it. But running at 220 water
temp vs. 180 will actually increate engine life if anything. These GM
engines are nearly bullet-proof mechanically. Hotter temps may lead to
shorter sensor life, but the mechanicals of the engine are happy to run
a little warmer.

Matt

 

Mine's an '88 305 V8 with a 3sp AT. I'm lucky if I get 11 MPG. I don't
drive it much anymore. No more than about 3,000 miles a year. It has just
under 180,000 miles on it. No cap either.

Eric

 

You knew I meant fuel-air mixture.

Well now. That depends on [how hot].

I think that's an overworked statement. If you start your engine dead cold
and rev it like an angry Klingon , you're asking for trouble. A good engine
will endure normal cold starts for 500,000 miles without measurable harm.

The higher the average engine temperature, the faster oils, greases,
coolant, rubber, valve faces and seats, exhaust system, etc. break down.

As long as the oil comes up to operating temperature every start, moisture
and acids will not accumulate. Ideally, the engine would reach ~220 for 5
minutes then cool down to ~150. But we all know that's not very practical.
For 1 thing, hotter running engines get better gas mileage.

 

You better get it fixed as you'd have to work really hard to get 11 MPG
from a properly tuned 305 - unless your 3,000 miles are spent plowing
snow or pulling stumps!


Matt

 

Bob Adkins wrote:

Running at 150 would be very bad for an engine.

Matt

 

I don't know what else to fix! The engine is tuned like a champ. The
tranny and rest of the drivetrain are all in great shape. I have some of
the normal rust on the bottom of the doors. Maybe the extra drag is
killing me?

Any ideas?

Eric

 

These are all fuel injected motors - no carb. The Buicks all got over
200,000 on them before being donated and the Malibu is currently at 125,000.
No shortened engine life here.

 

I'll second that Eric. I've never been a fan of the 305, but it sure should
get better than that. 11 is a real ouch.

 

Not if it were [made] for it.

I don't know how I got into this conversation, and I want out! :-\

All I ever wanted to say is that heat is the enemy of everything except gas
mileage. Engines are a compromise betwixt economy and durability. Everything
else I said was meant to show that, and I guess I botched it.

Man, it's 86 degrees out and just beautiful. My wife drove the new Sonata to
a doggone hen party when we could be out driving it.

 

What sort of driving do you do? The only time my truck dropped to 11
MPG was when the temperature sensor failed and the ECM was running open
loop all of the time. The truck had great power, but it coated the
inside of the exhaust pipe with a thick layer of carbon so I know
something was up. Another common mileage killer as a bad oxygen sensor.
If you haven't replaced either of these, I'd suggest a visit to your
local dealer and have them check things with their scan tool. My
temperature sensor failure didn't illuminate the MIL light, but it was
detected immediately with their scan tool.


Matt

 

Pretty much all city driving, and I am always hauling something.
Whether moving relatives, carrying home a load of mulch or stone, or
transporting an ATV, I almost always have at least a few hundred pounds
back there.

I just replaced the coolant and temperature sensors about 2000 miles
ago. And I had the truck on the scanner at the local Chevy delaer then.
All checked out fine except for the coolant sensor.

From what I have read, this mileage is not that uncommon for an '88 305.
It was the first year they switched from a real carb, to some pseudo-
fuel injection system. In fact, 13-14 is very common, and considering I
haul a lot, that may account for the difference. I also have very old
gas in there, but I do use fuel stabilizer which helps I guess.

I probably need to take her out on the highway for a while and should do
that one of these days.

Eric

 

Even a moderate load of 600-800 pounds can really kill your mileage.
Especially in town!