So today was the first day I got to actually drive my rebuilt 06 Cobalt SS/SC down to the inspection station to get it checked out. I filled up with Shell Premium before I started, recorded the info, reset my trip odometer, etc.

The trip to the inspection station was all highway, and I was moving at about 75 with cruise on, except for a little bit of boosted acceleration in 5th and some on ramp fun. I kept a close eye on my ECTs in the DIC. They were at 174-176 on the highway and went to about 180 in the city. I've never seen a car with ECTs that low. I traveled about 184 miles today and was left with a little less than half a tank by the time I got home. With some rough estimation, I figured I got about 20-22 MPG hand calculated, 21 DIC. Somethings up.

The car does have 91k on it and the previous owner was a godless, heathen bastard who never took care of her.

I'm going to put in a new ACDelco T-Stat this weekend. Only things I could think of that were possibly affecting it other than the ECTs were:

Spark Plugs
Fuel Filter
Alignment

Brakes are new and I do not feel any drag. Oil recently changed with Mobil 1. Air filter is a new AEM. I cleaned the TB and MAF. Tire pressures were set a little above placard spec. The car is stock, no stage kits. It seems to be boosting normally and I cleaned/lubed the metal rod on the supercharger boost thingy. Heat exchanger coolant pump seems to be working slowly but surely. I did have to add some coolant though when I got the car. The car does not immediately reach 12 psi but slowly gets there as the RPMs increase. Seems to boost more around 5-7 during normal driving. Vacuum lines are getting dried out and probably need replaced. How can they affect fuel economy with this system?

Any ideas guys? Do I need to do this?

 

20-22 on the highway? i avergae that in town, and low-mid 30s on the highway.
i got my plugs, air filter, fuel filter, and all that jazz new not that long ago

im also n/a but have a led foot

480 miles to a tank is best ive clocked. all highway, again i wasnt easy on her with the passing and crusing 20-40 km/h over the speed limit

 

Ive got full bolt ons and a conservative tune. I average about 28-30 on the highway and 20-25 in the city. In belleville which is a mix i usually average around 25. At school where its hilly as ****, lots of stop signs, and my commute is about 2 miles I average sometimes under 20. Im not an aggressive driver but I'll sometimes run it thru third pulling onto the interstate/spin the tires in town maybe once a week at the most, so by no means do I feather pedal it all the time

I havnt checked my plugs recently but air filter is clean(cold air) and alignment is one hunda

 

I'm knocking down 22-24 city, 32+ hwy in mine.

 

You guys, hes not asking what your driving style and average mpg is. hes asking for help

 

Anyway to determine your A/F ratio? also has it stayed low after you've driven more miles on it?

 

Don't drive it like you stole it/ thread.

 

I want you to write this down in a memo and entitle it "**** I already know."


In the winter, where are your average ECTs at, SS/SC guys? Mine were at 172-176. Seemed low to me. Is that pretty standard?

Problem is, the car was just put back into service after being rebuilt after an rear end collision, so I'm still trying to get a base line for everything here and then go from there. But on the first run out, the mileage was pretty dismal.

 

Not at the moment. After I replace certain things, if I'm still having this problem that will be my next step.

 

That was a joke. I would address tune up, clean the maf/tb, fuel filter, and run a bottle of lucas injector cleaner through it. I am sure it just needs some maintance. I had a F150 5.4 3v that the TB was dirty. It was acting weird, and was getting bad mpg. I did a tune up, cleaned the maf and tb, and did a fuel filter. It picked up a 5 mpg more. I would start there. Just my .02.

 

TB and MAF were done when I installed the AEM intake. I'm going to keep dicking with it and I'll let you guys know my results.

 

Pinky Demon, I filled up today with my 05 SS/SC. 99k miles. Zero issues. Straight city driving, and one dig race. I still was managing 24.7 according to the dash. I fill up once ever 2 weeks. We need to figure out whats up with the balt.

 

Oh believe me, I will. Thanks for giving me a heads up on whereabouts your city MPG is. I'm going to do this stuff in stages and see what works, so other users will have some reference.

 

25-26 combined in summer
22-23 combines winter. thats on studded tires, winterblend gas and letting car warm up longer because its ******* cold

i do drive like an ******* though. might have something to do with the lower mpg's :P

 

Any updates?

 

Nothing yet. It's been cold and it's not my daily driver at the moment. I'm thinking maybe next, next week I'll get to it. Going to replace the vacuum lines on the supercharger, pour some Seafoam into the tank, introduce top end cleaner into the motor, then change the plugs.

 

Report back after a second tank. It could be just not the greatest winter gas... But being so close to 100K If i read right a full tune up would be do!

 

Good luck. Sea foam works great. I had to do it to my LS1 Camaro at around 100k.

 

So I guess I'm really hanging up on these ECTs. It has been colder here recently around 25-35 degrees, and I've already replaced the T-Stat with an ACDelco product.

Car has good heat, it just takes forever to really warm up. When it does reach full operating temp, the ECT seems low compared to other vehicles I have owned. For example, highway driving it is at 170-178. Around town, it takes a while for it to even reach 150-160. Yesterday, I took a 5 mile trip across town, and when I got to my destination, ECTs were around 150. I popped the hood to check if either of the cooling fans were on and it checked normal. I suspect the coolant is original but I have no way to confirm nor do I think it would have that much of an impact on ECTs. This is the first all aluminum 4 cylinder motor that I've owned, and it just seems odd compared to everything else I've driven, especially given the fact that aluminum is supposed to rapidly heat up and cool down.

 

Mine takes some time to warm up also. It also runs around 178.

 

If you do a coolant change remember it's that weird GM stuff that turns to sludge if you mix the wrong stuff into it.

Are you shifting around 3k? That may be the other thing, I was getting bad mpg because the shift point was off too. You can also check to see if the cat is clogged because at that mileage especially with a Supercharged model it could have happened. Otherwise it should respond to everything your doing. Fuel Filters are often neglected can sometimes end up doing back to back replacements after 300miles because previous owner put foul/ethanol gas through it.

And fifth is not a good gear to punch in, the car struggles quite a bit not to go into boost around 80mph.

Coolant numbers are not that bad for a car in the cold. About what mine's getting if the fans even come on in OR. Rains so much it's like having a water submerged motor coolant system.

 

Do you just make up half the **** you say?

 

25mpg... i only get 18.8 MPG in mine.. 26 long distance, i just blame the engine note for the extreme usage of fuel -_-

 

My LT gets between 28.3 - 35.8 mpg, depending on how I treat the foot feed..... We are talking fill up to fill up, right? & not Avg mpg?

 

Yep, fill up to fill up. Once I get some more data, I'll post it on here.