I did an experiment the past 2 weeks and tried to stay out of boost, and shift below 2k RPM. I also kept it close to 2000-2200 RPM on the highway (not easy to do this in SE MI). I got about 27 MPG with a lot of stop and go driving. For 90% highway driving, I got nearly 33 MPG with my AC cranked up. The LNF seems to be quite an efficient little engine.

 

it's called direct injection, along with vvt (variable valve timing). Helps with fuel economy.

 

It also took a LOT of discipline... I normally drive with a lead foot and would get 23-26 MPG in the same conditions.

 

Sounds about right. On a highway tripped going down from NY to VA I got about 33. Going north to VT I went down to 28. Normal driving which is 90% 55 mph zones and 10% stop and go with using boost as much as I can I get 27.

 

not necessarily. You just gotta know what the conditions are for changing valve timing. Basically, once you start cruising, your pcm will decrease the amount of fuel your dumping into the cylinder by throwing some "filler" in there (unburnt exhaust gases).

Add to that the fact that because you're direct injected, it doesn't take much fuel to atomize as a normal multiport injection system (like on the other cobalts).

 

^^ As per GM's numbers the 2.4 is still 4 mpg better on the highway than the LNF and 3 mpg better in the city. LNF is 1 mpg than the LSJ on the highway though, again as per GM.

 

I was able to do a 36.2mpg (29 mile highway, 1.2 mile city) commute last week... my best one yet. Tires @ 42psi, AC off and pulse/gliding. I'm pretty sure I can do better but most of the time I'm late for work and in a rush. On my best runs I typically dont exceed 60-65mph.

If you get bored read some hypermiling sites and you'll be amazed what a car can do if you drive it right.

 

Why do you have your tires at 42 psi. Isn't that like 9 psi too high for stock LNF tires. I get that it would increase fuel mileage, but it would cause the tire to wear unevenly.

 

20 MPG here. Woohoo!!!

 

I run my tires at 29-30 psi cold, they heat up to 34 psi in the summer heat.
I found via my DIC that I can sustain 40 MPG if I cruise at 45-50 MPH. However, I cannot do that on a highway only on certain state roads until I hit a traffic light. I bet if I were to maintain 45-50 MPH on the freeway, I could get 38+ MPG easily.

It took a LOT of discipline to get 32-33 MPG. Class 8 Tractor trailers (fully loaded) were passing me on local roads and on the freeway.

 

I have them jacked up for fuel economy yes, and this week I'm going to increase them to max sidewall pressure. In between owning my 09 Coupe and now this 09 Sedan I had a 2010 Honda Insight, and tons of those guys are running like 55-60-65 psi and really no abnormal tire wear. According to them its a fallacy... but who knows as I'm not a tire engineer. I ran 8k miles in that insight @ 55psi and the depth on them was fine inside, middle and outside. Owning that Insight for 3 months really opened my eyes to how driving behavior really drags fleet fuel economy down.

I'm just having fun really, not much else to entertain me on a commute if it eats up these ***** stock tires oh well.

Thankfully starting in two weeks I'll live 1.5 mile from work now so I'll just bicycle to work again.

60MPH seems to be a real breakpoint for fuel economy on my Sedan.

 

What you could also do is get a set of the ss/na or sport rims with the 205 tires and pump them up and you would be even better than the 225 tires as I'm sure you know narrow is better for fuel economy.

 

If you go to fueleconomy.gov and use the "new" 2008 estimates, it's a little closer.

City/Highway/Combined

22/32/26 2.4 (2008)

22/30/25 LNF (2008)

20/28/23 LSJ (2007) (22/30/25 on original 2007 window sticker)

 

The 2.4's 2008 EPA estimates are slightly less than what I'd get with the LNF, and my SS/TC tires are deflated by about 1-3 PSI to improve tire wear.

 

My best ever was 29.1 MPG... on my Pontiac G5. This car, I'm getting 24 MPG (and I'm using Oct 93 vs Oct 87)... Maybe it's just me, but I can't seem to stay off the boost

P.S. This was with combined city/hwy driving. And the G5 was a manual as well. If it's not a manual, I refuse to drive it

 

i just drive mine dont pay attention to throttle / shift point just drive the way i feel and i average 26 or so MPG... no complaints i dont have the discipline to do what the OP did