Ok, so it's official.. My MPG is actually fallin at a steady rate I don't speed excessively, but when I do, I cruise highway at bout 80-85. Other than that, I drive on post(spd limit 30-35) but most of my miles are highway miles(6663 earlier today)
I've only gotten V-power at shell since I've gotten the car(August) except for twice when I filled up at the shoppette

O, I got an 09 SS/TC... and it's Black if that helps

No huge work done to my car... Here's the timeline...
-92 mi when I got it...
-Dealer replaced the intercooler at bout 2k miles cuz I bottomed out goin up a hill an scraped it
-K&N drop in at about 2.5k
-Crown shifter boot
-local dealer replaced entire transmission at bout 4.5k cuz they were bein one of my stabalizers went bad and they were tryin to be dicks and hold my car for 2 months but I talked to GM and got a free tranny
-Installed Injen charge pipes at 4.5k

k Now here's where **** starts goin bad...
Somewhere between then and now, my mpg has just been droppin, I've been at the pump more and more an it's almost as if I have a fuel leak or somethin. My car's just been supa thirsty!
My drivin patterns havent changed, and I'm still on the highway all the time(Austin and back, or San Marcos an back... (1 hr-2 hr)
I usually look at the inst mpg and that's dropped from around 33-28highway/18-22 cty to 24-20 highway/12-20 city(if I'm lucky)
I just got my oil changed Last tues (nov 30) and it's still not helpin..
My car says avg. mpg is 23.4 right now and thats down from 25.3
Actual MPG frm Nov was 21.7
I haven't rotated my tires yet as suggested by onstar lol but I don't think that its gonna help much..
I saw somethin bout someones mpg goin down in the winter but... I'm in Texas, its hasn't been that cold yet lol

I'm callin the dealership tomorrow to see wat they say, but they'll praly want me to bring it in an hold it for another month
Heeeelllllppppp

 

is it because of dropping temperatures? i know the warmer the intake air the better the gas mileage usually...

 

Maybe.. but it seems like it's droppin a lot just from the temp drop

 

winter mix gas?

 

Well cold air is denser than warm air. So it takes your car a little more effort to push through it than warm air. Colder temps also could mean:

- Your tire pressure is too low
- It takes your engine a little longer to warm up to the optimal temp range.
- Most people leave their cars in the driveway to warm up. Doing so means you're getting 0 MPG. Today's cars can be driven practically from a stand still in most conditions.
- Winter blend gas which robs mileage as well.

 

NOPE wrong, the LNF needs to be up to a good running temp at very least done with the cat warm cycle and up to about 100 degrees or it will run like crap and misfire.

 

In addition colder pavement makes colder tires, which makes more rolling resistance. Check and adjust air pressure as necessary.

Does the K&N need service? Has it been over oiled and has your MAF dirty?

 

So keep your foot out of it for a mile or two, but don't let it sit idling in the driveway for 15 minutes....

 

This.

Most cars will run like crap if you push it while it's not up to temp. Baby it for a few mins and it should be just fine. Plus when the car is sitting there the gearbox isn't getting warmed up.

 

you smell any gas coming from your car?if so maybe its a bad fuel pump

 

I keep track of my tire pressure an it has dropped a lil bit, but It's still good, and no I havent cleaned my filter yet, an my MAF is clean, I checked earlier

What's Winter mix gas?? An if you get less milage, why would you use it??

I do let it warm up for a while now, but in the summer/early fall, it seemed like I was sittin in my car a lot and not goin anywhere..(highway trafic, waitin for people.. jus lettin it sit.. **** like that) so it kinda evens out. And no, no gas smell

 

Winter mix or blend gasoline is the blend they sell during the cold months. During the summer they add different additives to the gasoline to stop the emmisions from chemically bonding to other gasses or pollutants in the air and thus producing less ozone (smog). Apparently it doesn't run well in the winter though due to the chemicals that are put in it for the summer which make it more difficult to vaporise in the winter. Something along th lines of that.

Not sure why it gives less MPG, but thats what it is.

Joel

 

It does not take 15 minutes just 5 in most weather. If I give my car more than 1/8th throttle it sounds like a civic and accelerates like one. I would rather let the car warm up the way it is supposed to than risk it, Unless you have an LNF you have no Idea what I am talking about.

 

This!! Even when it was hotter than hell i would still let mine warm to at least to 100,which didnt take long

 

Winter gas contains more volatile components to help the fuel to vaporize when cold so it is easier to start. Summer gas is less volatile(doesnt evaporate as easily) to help prevent vapour lock and reduce emissions. The lighter compounds have less energy and your mileage goes down.
Be happy your not driving an Envoy XL like my wife. MIlage goes down to the low teens in the winter

 

you basically cant drive an LNF car unless its out of cat warm up at minimum... it'll spit and pop if you do more than BARELY touch the gas... and then it'll surge and all kinda happy stuff... i usually wait for my RPD to show the fuel pressure swinging back and forth before i drive... now that its colder it takes longer for the wideband to warm up so i just wait for the car to idle down to under 1000 rpm and then im good to go... my MPG has gone to ISH as well but i'm pretty sure its from me doing MAF tuning and fubaring it all to hell...

 

my cars average mpg reads 18.2


/Thread

 

As mentioned already, winter blend gas will drop you 1 to 2 MPG especially in a FI car. Add in the longer warmup in the morning and you have an easy 2 to 3 MPG drop.

Also, I would not recommend driving the LNF without letting it warm up for at least 2 minutes first. This is for two reasons: 1. While cat warmup is in place the valves are overlapping big time. This will cause some horrible spitting, sputtering and backfiring. 2. The LNF is direct injected. Direct injected cars actually NEED a warm engine to help with fuel atomization and combustion.

 

hmm... ok, I think i get it. Yall are sayin the same thing the tech at the dealership said.. bout the winter fuel and the air bein denser. I wanted to get tuned sometime soon, but I guess I should wait till it warms up huh?

 

I have an LNF. I get in the car, I drive the car. I keep my foot out of it for a few miles. My car doesn't buck, ping, fart, sound different or otherwise give me any trouble whatsoever. No idea what you're going on about.

 

Watching my Wideband I notice that when I first start my car, my
AFR is rich, then slowly leans out to stoke after a few minutes.
I let my car get up to 100F before loading the engine. I have
one interceptor set with the annuncator lights to come on
below coolant temp of 100F so that when they go off
I know im warm
So ya, less MPG in the winter.
In the summer, my coolant is already 100F sometimes more (When its 105 outside)

 

Same, I wait till 100 or so which in cold weather takes about 5-10 min.

 

sad to say mines 17 MPg lol

 

You guys have no idea what your talking about when it comes to the LNF. You have it all wrong. 1) there is nothing wrong with driving the veichle when its cold. GM spends millions of dollars on testing it extreme conditions. Im talking conditions at like- 200 F. 2) the cat warm up cycle isn't designed to warm you engine. Its designed to heat your catilytic convert up to temperature to reduce emissions. Hence the name" cat warm up cycles" not engine warm up cycle

 

I don't think anyone said the cat warm up has anything to do with the engine warm up, I did mention that while the car is in cat warm up the valve overlap is MASSIVE and plays havoc on airflow.

I also beg to disagree that a cold DI engine runs great in extremely cold weather. Until my oil gets up to about 100F (which only take about a minute or two) the car does not run well at all. I was worried at first that something was acting up, so I did some research on the engineering aspects of DI engines. In doing so, I discovered that DI engines run better when the engine is warm as the fuel atomizes better. DI engines require fuel to be as atomized as possible for the most efficient combustion, not to mention it is good for the engine to let the oil warm as much as possible before driving anyways.

If anyone is worried about the .4 ounces of gas they are "wasting" by letting your car warm up for two minutes, then by all means start it and go.

FYI .4 ounces is about $.01 when gas is $3.50/gallon. So, $.01 * 2 cold starts a day * 7 days a week = $.14 a week to let your car warm up. Average about 16 weeks of "cold" weather per year = $2.24/year in wasted gas. A rebuilt motor is ~$1500. I will take my $2.24 of "wasted" gas as chalk it up to my own piece of mind. I definitely won't be losing sleep worrying over what I may have done with all the gas money I would have saved if I just didn't let my car warm up for two minutes.