Speed vs. Fuel Economy - 2004 Chevrolet Aveo sedan (1.6 L, 4-sp automatic)

[slowbro]

Originally Posted by Sven7

Thanks Kodak for that graph. Aveo, does your car have manual mode? That could be very useful.

Also, I'm kind of disappointed at the EPA for GM's "economy" car- combined is only 2MPG better than the Probe. You'd think it would be more eco-minded!

I can select and hold my car in 1st, 2nd and 3rd gears but I can't hold it in 4th if I go under the speed that it's supposed to shift at (I can't upshift early).

Although since I am able to select and keep 3rd gear, it might be more fuel efficient to shift into 3rd earlier than it normally would as I'm accelerating. I've recently been getting used to "foot-shifting" my car into the gear that I want, but maybe I should try using the gear lever too.

As for your other comment about GM's "economy" car, I agree. The 2004 Chevy Aveo was sold having the worst fuel economy in its class. It kind of makes me frustrated when I tell people that my best tank was 34 mpg doing combined driving, and they aren't the least bit impressed because that's what they expect my car to be able to do. Maybe people will start paying attention when (if) I start getting 40 mpg (Time to work on the aero mods).

OTOH, I do like the fact that GM is getting better. The new Sonic (Chevy Aveo replacement) is expected to get 40 highway. That's right on par with the Focus and Fiesta and it's better than the Yaris. Chevy has improved a lot since 2004 (can't wait until the Cruze diesel comes out).

[Kodak]

Originally Posted by Aveomiler

It kind of makes me frustrated when I tell people that my best tank was 34 mpg doing combined driving, and they aren't the least bit impressed because that's what they expect my car to be able to do. Maybe people will start paying attention when (if) I start getting 40 mpg (Time to work on the aero mods).

Beating the EPA highway rating (31 highway for an 04 Aveo auto) by 3 mpg is still a success. You're almost 10% over the highway with your combined tank. Considering you have an automatic transmission, I'd saying you're doing very well with your current setup.

[slowbro]

Thanks Kodak, and thanks for the graph.

[Kodak]

No problem. It gave me a chance to procrastinate without feeling terribly guilty.

[Geonerd]

I don't know if you can get terribly accurate numbers over such a short distance. (Your numbers do seem to be somewhat noisy.) Any chance you could repeat the experiment using a longer road?

[Thymeclock]

Originally Posted by Aveomiler

I can select and hold my car in 1st, 2nd and 3rd gears but I can't hold it in 4th if I go under the speed that it's supposed to shift at (I can't upshift early).

Unfortunately, you are misinformed about your car's transmission. I also have an Aveo ('09) but it has the same automatic transaxle as yours.

The "hold" button does not work for the higher gears, or the way you think it would - it is only meant to keep the car in a lower gear when on ice or snow so you don't spin your wheels.

Although since I am able to select and keep 3rd gear, it might be more fuel efficient to shift into 3rd earlier than it normally would as I'm accelerating. I've recently been getting used to "foot-shifting" my car into the gear that I want, but maybe I should try using the gear lever too.

Again, your perceptions are not correct. I have done a lot of research on this and the problem is with the way the transmission is programmed. The tranny is a 4 speed and is electronically controlled, but unfortunately the shift points cannot be changed. However the biggest problem for fuel economy is the set point for it to go into torque converter lockup. On most cars this happens at around 40 MPH. On the Aveo (and some other Chevy models) this does not occur until 45 MPH - which is way too late if most your driving is being done at 40. When it does lockup it actually feels like a shift - you will see the RPM's drop and suddenly your MPG goes up dramatically.

As for your other comment about GM's "economy" car, I agree. The 2004 Chevy Aveo was sold having the worst fuel economy in its class.

Not exactly. The figure for highway MPG is correct and it is excellent at 37 MPG. But the figure for city MPG is inflated - it was probably 24 and the best you will get is 22 MPG, which really sucks. The very wide disparity between city and highway mileage is due to the late TC lockup. (AKA a "slushbox".)

It kind of makes me frustrated when I tell people that my best tank was 34 mpg doing combined driving, and they aren't the least bit impressed because that's what they expect my car to be able to do. Maybe people will start paying attention when (if) I start getting 40 mpg (Time to work on the aero mods).

Forget the aero mods. I tried, and it won't help. What we need is way of controlling the programming of the transmission to get it to do the TC lockup sooner.

[slowbro]

Thymeclock, yeah you are right about not being able to upshift early with the hold button. I guess I just have to stick to footshifting my car.

Originally Posted by Thymeclock

Not exactly. The figure for highway MPG is correct and it is excellent at 37 MPG. But the figure for city MPG is inflated - it was probsbly 24 and the best you will get is 22 MPG, which really sucks. The very wide disparity between city and highway mileage is due to the late TC lockup. (AKA a "slushbox".)

What are you talking about? The EPA highway estimate for a 2004 Chevy Aveo sedan with automatic transmission gets only 31 highway, not 37 so it's not "excellent" highway mpg. The city estimate is 23 and I do agree that it might be inflated, but overall, compared to other cars sold in the same year the Aveo was not brilliant in city or highway fuel economy.

[Thymeclock]

Originally Posted by Aveomiler

Thymeclock, yeah you are right about not being able to upshift early with the hold button. I guess I just have to stick to footshifting my car.

I don't understand. You have an automatic transmission, right? What do you mean by "footshifting"?

What are you talking about? The EPA highway estimate for a 2004 Chevy Aveo sedan with automatic transmission gets only 31 highway, not 37 so it's not "excellent" highway mpg. The city estimate is 23 and I do agree that it might be inflated, but overall, compared to other cars sold in the same year the Aveo was not brilliant in city or highway fuel economy.

Despite all Aveos having the same engine and transmission, apparently there must have been some other tweaking done over the lifespan of the model and the way the gov't jiggers the numbers. My '09 actually does get 37 MPG with the A/C on at 65 MPH. That is better than other comparable cars of its model year, so it's hard to complain about that aspect. And that high EPA figure is how GM promoted the car to compete with other models such as the Yaris, the Fit and the Rio. But the city FE is worse than the EPA estimates. That's disappointing, particularly if you do mostly city driving, as we do. It wasn't until after I bought it that I could discover the reason why.

[slowbro]

Thymeclock,

By "footshifting" I mean taking my foot off the gas a little and applying it back on to get my car to upshift. Normally when I accelerate, the car would just stay in the lower gear but when I do this I can get it to upshift, but it can only be done at speeds the car would normally shift at when I'm not accelerating. I just call it "footshifting" because I don't know what else to call it. I guess that does create some confusion so sorry for that.

Although I am a little disappointed in my car's EPA rated fuel economy, I do like the fact that the newer Aveos got better gas mileage. It shows improvement on GM's part. I would really love to get a new Sonic since they get great fuel economy (29/40).

[Thymeclock]

Originally Posted by Aveomiler

Thymeclock,

By "footshifting" I mean taking my foot off the gas a little and applying it back on to get my car to upshift. Normally when I accelerate, the car would just stay in the lower gear but when I do this I can get it to upshift, but it can only be done at speeds the car would normally shift at when I'm not accelerating. I just call it "footshifting" because I don't know what else to call it. I guess that does create some confusion so sorry for that.

It's usually referred to as "inducing a shift" and that is a useful strategy. With the Aveo we have found that often it is best to accelerate briskly to get into the higher gears as soon as possible. Accelerating slowly does not help at all, for the lower gears are really fuel consuming.

Although I am a little disappointed in my car's EPA rated fuel economy, I do like the fact that the newer Aveos got better gas mileage. It shows improvement on GM's part. I would really love to get a new Sonic since they get great fuel economy (29/40).

I thought that too before buying the '09 Aveo. However the city MPG estimate is totally unrealistic. Since GM is now Government Motors, the figures for the Sonic might also be inflated. Unfortunately there is no way of knowing for sure until you own one.