Since the weather has turned cold my Lesabre mileage has dropped from 30 to
23 MPG Highway and from 22 to 16 MPG in town. The dealer recently replaced
the Air mass senor, fuel regulator, air filter and cleaned the fuel
induction system. They can't find anything else wrong. I was getting 30
highway and 22 in town.
They said that it was normal for the mileage to go down in the cold weather
that until the engine warmed up to 195 it would get poor mileage. The
temperature never gets above 187 and normally is about 180 and that's after
one or more hours of continuous driving .
Any suggestions. The temperature averages about 20 degrees lately.
#1 Winter fuel mix, lose around 1-2 MPG
#2 Longer winter warm up time, lose big mileage first 5-10 minutes of each
drive, if your drives are only 30 minutes long, I would guess another 1-2
#3 Low tire pressur due to cold, even a loss of 3 psi, almost 10%, will
cause a drop of up to a few MPG.
180 would be expected at the minimum end if the outside temperature is under
30 degrees F and you were cruising at highway speed. The simple air speed
through the radiator when it is that cold is going to lower the engine
temperature. Plus the cooling effect of the additional cooling in the
heater core. Add the air conditioning compressor load when you have the
defroster on as well for additional losses.
I would bet if you cover all the above usual winter losses, that what you
are experiencing is probably pretty much normal. Most people experience
around a 15% loss in MPG during continued winter temperatures below 30
degrees. Add low tire pressure and you are killing the MPG. Driving
through snow around town also reduces MPG as well due to the extra drag load
of driving through the slush.
I didn't start taking fuel mileage until engine was warmed up after 30
minutes. I check the tire pressure everyday and is set at recommended level.
Mileage was compared was with air-conditioning running in summer. The reason
I started checking it was because of the dramatic decrease in MPG when the
Air-Mass and fuel regulator went bad. Dealer had mentioned normal Temp when
warm as 195. I had a dodge ram before this and it always warmed to normal
operating temps throughout the winter. I know each auto is different was
wondering if I should partially block the radiator so it would run in the
normal temp range?
I would then have the dealer test the thermostat to make sure:
1. It is not stuck partially open.
2. It is opening at the correct temperature.
I would also be very suspicious of the condition of the coolant if it has
never been replaced through three winters. Not the protection provided, but
the all too common start of sludge build up by air entering the system,
intake manifold slow and small leaks, improper adding of the wrong coolant
or non-distilled water to top off the system.
In any case if they replace the thermostat, make sure to ask that they flush
and fill and then bleed the cooling system per GM's instructions.
Bill, I assume that is the 3.8L engine. First, yes, fuel economy will decrease
a bit during cold weather, especially if you are driving it short distances. I
have the Park Ave. with 3.8L, and once I have driven it ten or fifteen miles in
any weather, the coolant temp will be over 195 F, generally either 197, 198, or
199. So, is there any possibility of a cooling system problem on yours, like a
stuck thermostat? This is a small item, but check to see if your tires have
proper pressure. They tend to get low when the weather suddenly gets cold.
On mine, I'll get about 35-38 mpg on the highway.
I hope this doesn't sound like a troll post, but I personally find it very
difficult to believe that a Park Avenue (or any other mass produced vehicle
with the 3.8) could achieve these astoundingly high fuel mileage ratings
unless the vehicles was coasting downhill at 45 MPH with a tailwind the
entire trip. I certainly do not have the most fuel efficient driving habits,
but I've known precious few who have been able to meet or exceed EPA
estimates. If my memory serves me correctly, the highest highway EPA ever
issued on a Park Avenue was 30 MPG. Assuming your claim of 35-38 MPG on the
highway is correct, are you obtaining these numbers from the vehicle's trip
computer or driver information center? If so, I'm sure you're aware these
often read on the high side and are good for little more than "blinky
lights" or to assist with developing fuel efficient driving habits. Every
vehicle I've owned with a trip computer or driver information center has
consistently read anywhere from 1-5 MPG higher than the actual amount as
derived from dividing fuel consumed into miles travelled.
I'm not denying your ability to obtain these figures, but I am curious as to
what your secret is to obtaining them assuming they are correct.
I understand your surprise. First of all, a little history. I had a 1991 Buick
Park Avenue 3.8L, and it was an excellent road car. Between San Jose and
Bakersfield or Las Vegas, round trip, I could consistently get 36 to 37 mpg.
The trick there was that I was driving slow, about 57mph, and trying to get as
much draft as possible from the 18-wheelers blowing past me on I-5. Then I got
the 2002 Park 3.8L, and it is an excellent road car also. The electronic
computer shows it getting 38-39 mpg to Bakersfield, but the actual calculation
turns up more like 36-37 mpg. The change there is that the sweet spot is at
about 60-61 mph for economy. The EPA rated highway economy is 29, but I cheat
by going slower than everybody else. Oh, and I did not say that I stopped at
all of the red lights or stop signs. It is not unusual for me to drive with the
cruise control engaged continuously for 6-8 hours. If I drive "hard" to Las
Vegas, the mileage will be about 30 mpg, even though I never stop the engine.
Around town economy is about 20-22 mpg.
Bob also calculates his MPG using a solar powered Radio Shack calculator
that has gradually gotten weaker over the years...........lol
I couldn't resist.
1991 Pontiac Bonneville LE
Actual mileage in my case. I get 28mpg on the highway at 70mph. If I
drop down to 50mph and do the egg on the accelerator routine on perfectly
flat ground, I can keep my speed with the engine in overdrive and ~1400rpm.
I squeezed 40mpg one time doing this. It's all technique. To get maximum
efficiency, you need to accelerate about 2mph per second - and let the
car shift into overdirive at about 35-40mph. Stomping the gas like we
all like to do - not so much.
If the engine never goes above 2500prm, you'll get at least 25mpg.
Yes, I agree. Drive with one eye on the tachometer, not the speedometer. You
can actually cruise down the highway at 1400-1500 rpm. And I agree about
increasing speed. I leave my foot off the gas pedal, and increase the speed
with clicks on the cruise control, and that is very slow. The 3.8L engine can
be very economical, but then there are driving techniques that will help. I
think the original poster has something sprung in his cooling system, so his
engine is never getting up to normal temperature.
I have a 2001 Lesabre with the same engine. Here is my experiance with it so
far, after about 1.5 years.
Engine temp: always stabilizes at about 195 once the engine is warmed up,
summer or winter. Takes a bit longer in winter time to reach this, about 30
summer highway ~ 37 mpg CDN gallons = 31 mph US gallons
summer city ~ 22 mpg CDN gallona = 18 mph US gallons
winter highway ~ 35 mpg CDN gallons = 29 mph US gallons
winter city ~ 17 mpg CDN gallons = 14 mpg US gallons.
Living on the Canadian preries I find that after an engine is warmed up, the
winter highway mileage does not drop very much once you are crusimg at 60mph.
The city mileage is a different story, it starts to drop dramatically as
tempetures go down. Presently we are around high of 25F to about low of 0F
(-5C to -18C)
I have a new thermostat to install 192/195 rated. My engine temp is
stabilized around 180 once warmed up. I did notice if I sit in traffic the
engine will warm to 195, but as soon as I start moving again it drops to
180-182. I will install the new thermostat this coming weekend.
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