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[Rybuck]

as do i...i've been out with big trucks before and mine fairs out better

[zeuce]

ok ummm a little off topic arent we cough cough 

[Rybuck]

yes it was sorry Chris!

[hikeetech]

Updates, so after my trip to Baie-St-Paul and back, I have been getting my normal winter mileage which is about 550/tank. This might due to 1)all highway driven 2)the injection system cleaner I put in 3)nice weather
Now I am back so we will see how my truck does in the city.

[hawkeye]

I've noticed both here and on c-fans that quite a few members report a significant decrease in mileage over time. While there are the obvious culprits such as heavier tires, colder weather, winter gas etc. I wonder if anyone has found a simple fix for an unexplained decrease in mileage? I'm thinking something simple like a fouled o2 sensor or fuel filter kind of thing.

Any thoughts? It'd be beneficial to compile a list of possible sources for bad mileage for some of the owners of the older models who are having huge variations in mileage, and it'd be nice if we found a simple fix (like the injector cleaner above) for much of the poor mileage members are experiencing.

[hikeetech]

Sometimes its just the gas itself, some gas station offers better quality gas than the others. The two times I got very bad mileage, I filled up at a nearby Shell.

[zeuce]

other than winter fuel, bad gas mileage can be caused by a plugged/dirty fuel filter, clogged air filter, spark plugs, mis reading o2 sensor, and dirty injectors. I flush my fuel injectors every 50,000 kms to keep them tip top. It's suggested to be done every 80K. I use (at my work ) a fuel flush machine that properly backflushes the fuel rail, injectors and valves and cumbustion chamber. My machine is from snap on but most shops carry motorvac. This is the best way to clean your fuel system, sorry but IMO the bottles you drop in the tank are temporary.

[hikeetech]

Just out of curiosity, how often do you guys change the fuel filter? (Im too lazy to check the owners manual)

[zeuce]

Im actually not sure what gm recommends but I change mine every 50000kms only because we get bad gas in the north and we get alot of moisture in the winter.

[CanyonAB]

I changed mine at 60,000km and didn't notice a whole lot of difference. My truck is an '05 though so it's like a $12 filter and can be changed in literally 10 seconds so meh.

As for mileage...the best I was getting was when I had my exhaust only, but my foot has grown heavier as I've increased horsepower. I'd bet best fuel mileage would result from MBRP exhaust (best performance gains so I'd bet best fuel economy increase if you keep your foot out of it), Supermod ported TB, and dyno tune. The intake increased power, but I noticed no fuel economy increase with it, or with the header for that matter. No decrease with them though, unless you're stomping on it to feel/hear the difference over stock.

[muddincolly05]

I know this thread has been dead for a while now but I was wondering if anyone has anymore info on the cause of the bad mileage.Right now with a mixture of city/highway driving I am getting roughly around 250-300 km to a tank.I replaced the fuel filter about 4000 km ago air filter about 2000 km oil was just changed 2 weeks ago.I normally get 550-600 per tank in the summer so it is quite a big difference.

[hikeetech]

I know this thread has been dead for a while now but I was wondering if anyone has anymore info on the cause of the bad mileage.Right now with a mixture of city/highway driving I am getting roughly around 250-300 km to a tank.I replaced the fuel filter about 4000 km ago air filter about 2000 km oil was just changed 2 weeks ago.I normally get 550-600 per tank in the summer so it is quite a big difference.

Same here, I am getting a little over 300km to a tank. I think there are various reasons causing bad mileage due to:
1) winter, cold ambient temp.
2) gas quality
3) longer idle time to warm up vehicle
4) extra weight in the truck bed to increase traction
5) takes longer to warm up tires
...

There are probably more...

[zeuce]

top 3 in your list are prolly the biggest influence in bad gas mileage in the winter

[muddincolly05]

First 2 for me then since i know how horrible for mileage it is to let the truck idle in the winter I try not to do it at all.Truck warms up pretty quick so its not too bad. I noticed that it seems to be burning pretty rich lately too.new O2 sensor help any maybe?