fslick

Hi guys. I think my gas mileage is messed up in my car. My avg is 10.7 L/100km, which is a bit high (and i dont usually get on the gas too much). This is mostly city driving with minor hwy for a short period of time.

Now the main issue i have with this is that when DFCO kicks in, my instant L/100km reads only about 6-7L/100km. I thought DFCO means that you coast using no gas while in gear, and I read somewhere that other people get 99MPG while doing this, so why am I not getting 1L/100km? I think the fact that I am not getting a correct milage reading for DFCO is the reason for my higher L/100km.

Before you ask, yes i do know that I have to be above roughly 1500rpm and be travelling at least over 20km/h. What do you guys think?

edit: I drive a 2009 cobalt SS coupe

jlong3382

Whoo.....you guys do thing backward in Canada. L/km

DaBuzzard

Nah, you 's got it backwards

10.7/100 is not great but, for mostly city driving, not unexpected. I get high 6's low 7's with 130 km daily commute, all highway.

If the dfco is working, you should see 0 L / 100 km on the dic. Found mine is hit and miss, will usually cut in on the highway when I get off the throttle but sometimes it won't. Very intermittent, along with the rev's "hanging" between shifts and when coming to a stop. Dealer has no clue on this one

How hard you accelerate, how high you wind it before shifting, how much weight you carry in the car (more critical in town than on the highway) are all going to affect the mileage.

You don't say what engine / transmission you have - a 2.4 auto will not get as good of mileage as a 2.0 5 speed will assuming you stay out of the boost. As well, the 2.0 and 2.4 do seem to get a bit better mileage with premium fuel, stock 2.2 won't gain anything.

You might want to track your mileage manually, I have found the dic to be about 3% optomistic on the mileage.

fslick

So i dont think the reading is accurate, I have NEVER gotten 0L/100km. I went coasting downhill on a mountain going 90km/hr and I could only get down to 1L/100km.

I drive an 09 SS btw (5spd). Even when I let off the gas on the highway in 5th gear it only goes down to like 3-4L/100km. I dont think I should be getting such shitty mileage because I honestly dont accelerate that fast when Im just doing normal driving. I will try to track my mileage manually next time.

jlong3382

You know guys come to think of it, I've had friends, who don't drive cobalts, who say they get 99 mpg when they coast. I've never gotten that with my cobalt. the most I've ever gotten has been like 60 mpg......idk what that translates too.............................and yes you guys are right. Compared to the rest of the world, we 's measure everything wierd.

DaBuzzard

The last hold outs

Well, except for the British. The buy their "petrol" in litres, their meat in grams / kilograms, they weigh themselves in "stones", they buy beer in imperial pints (bigger than US pints), their speed limits are in miles per hour......and then they drive on the left side of the road.......what a dogs breakfast

At least the has stayed with a single system

To fslick - you likely won't see the dfco kick in around town, and there is a bit of a lag in the dic, seems to take a couple seconds to update so it may not be the best indicator.
Tempted to get some sort of data logger and monitor the idc's, afr, and tps - see what it is REALLY doing

fslick

so if theres a lag, then my mileage is essentially reading higher than it actually is?

DaBuzzard

Could be but it lags a bit both ways. When you get off the gas the dics takes a couple of tics to show the increase in mileage, same when you get on it - it takes a bit for the display to show the increased consumption.

Easy way to track your mileage manually - next time you fill your car, fill it unitl it clicks off, don't "top it up", reset one of the trip meters (I use A) to zero. Drive the car like normal, when you need gas, go to the same station and the same pump, fill as above.
Note the mileage on the tripmeter, reset it. Note the litres. Crunch the numbers and voila!

By using the same pump every time (if you can) it should click off at the same level and give the most consistant results.

I note my average economy at the same time (and reset it every tank) and comparing over 29000 km the dic is 2-3% high every time.

Another thought occured to me - when I set the display for miles / gallon instead of L/100km, I see 99mpg (dfco working?) far more often. Maybe there is a little bug in the software driving the dic?

umrdyldo

iTrader: (1)

What the hell is that?

DaBuzzard

Dogs breakfast = really #$&%ed up mess.

Sorry, my age shows sometimes

fslick

K i will try that method. But just so u know, there isnt really a lag when I get on the gas (like it jumps up FAST). When I coast in neutral I actually get better mileage according to the DIC which should not be true if DFCO is kicking in. Ill see if it actually goes to 99mpg tho.