Two tanks in a row w/over 29 mpg in my truck!

[5speed5]

It's a 2005 Chevy Colorado 4WD with 3.5L 5-cyl engine and 5-speed manual tranny. 29.26 mpg followed by 29.40 mpg. Not bad, but I was hoping to break 30. My only mods so far are tires at 40 psi and smooth hubcaps and I used EOC for both tanks. (Used it sporadically prior to that.) EOC doesn't work as well for this truck as it did for my previous vehicle (Pontiac Vibe, 47+ mpg...never tried EOC on my Metros). This truck coasts like a pig! The driveline is just not as loose as a car's (it's got over 80K miles and should be "worn in" by now).

It took a long time to get through two tanks as I drove my Trailblazer most of the summer (because I had to take kids to camp everyday). It took 2 mos & 6 days to go the 538.9 miles of this tank and a little under 1.5 mos for the previous tank of 540.7 miles.

Next mods are electric cooling fans (currently has mechanical clutch fan) and a tonneau cover (probably homemade)...not necessarily in that order. Hoping to break 32 or even 33 mpg with those mods next summer.

Edit: Made it over 30 mpg see 9-24-10 entry below

[06colorado]

That is some good MPG for a Colorado. I've got a reg cab 4cyl auto 2wd and best I got was 27.3. Do you have a pic of the hubcaps?

[06colorado]

Oops, just found your thread about the hubcaps.
Another question, do you have any engine mods done? (intake, exhaust, tune, synthetic fluids...)

[5speed5]

Originally Posted by 06colorado

Oops, just found your thread about the hubcaps.
Another question, do you have any engine mods done? (intake, exhaust, tune, synthetic fluids...)

No engine mods at all yet and just regular Valvoline 5W30 oil.
I just added a homemade tonneau cover yesterday, but that was obviously after the two 29 mpg tanks. Keeping my fingers crossed that the tonneau
will bring me up over 30 mpg before the weather gets cold.

(The tonneau cover cost me ~$80 for all materials at home depot.
If you're interested, I'll take some pics of it. It's a very simple design,
no drilling in truck, very light, etc., but still pretty user friendly)

One thing you should know is that I'm at high altitude (~7000 ft average).
That definitely plays a role as it effectively turns my 3.5L engine into a
2.8L (there's about 21% less air up here...less air means less fuel) and it means less wind resistance. I also have a pretty favorable commute as it's all rural highway (50-55 mph) with some good hills. The hills enable me to use DFCO and EOC at strategic spots. It is, however, only about 9 miles if I take the long way, so I don't get the long commute advantage and my winter mpgs will go way down as the engine will take the first 5 miles just to warm up.

[06colorado]

Good information there. I had no idea about the air and how it would make the engine seem smaller.
I'm sure after some of the engine mods like intake and exhaust you'd be over 30mpg.

[cons]

Originally Posted by 5speed5

No engine mods at all yet and just regular Valvoline 5W30 oil.
I just added a homemade tonneau cover yesterday, but that was obviously after the two 29 mpg tanks. Keeping my fingers crossed that the tonneau
will bring me up over 30 mpg before the weather gets cold.

(The tonneau cover cost me ~$80 for all materials at home depot.
If you're interested, I'll take some pics of it. It's a very simple design,
no drilling in truck, very light, etc., but still pretty user friendly)

One thing you should know is that I'm at high altitude (~7000 ft average).
That definitely plays a role as it effectively turns my 3.5L engine into a
2.8L (there's about 21% less air up here...less air means less fuel) and it means less wind resistance. I also have a pretty favorable commute as it's all rural highway (50-55 mph) with some good hills. The hills enable me to use DFCO and EOC at strategic spots. It is, however, only about 9 miles if I take the long way, so I don't get the long commute advantage and my winter mpgs will go way down as the engine will take the first 5 miles just to warm up.

How confident are you on that altitude figure?
I'm trying to figure out how my 2.3L Ford Ranger is getting 60 mpg hwy in Jackson, WY (besides all the aeromods). So my engine is really like a 1.85L here at 6,500 ft?

[5speed5]

Well, according to this chart:
Air Pressure and Altitude above Sea Level

It says 7000 ft would be 586.7 mmHg while sea level is 760 mmHg.
So, 586.7/760 = 0.772 or about 77% of the sea level air, so I was a bit
on the low side with my 21% figure. It's actually 23% less air at 7000 ft.

6500 ft is closer to 21% less air (taking the average of the 6000 ft and the 7000 ft
pressure), so your 2.3L is actually a 1.82L.

[5speed5]

Made it over 30 mpg at today's fill up. 570.1 mile tank (my best yet), 18.492 gallons gives 30.83 mpg. I added the tonneau cover 201 miles into this tank and then swapped out the mechanical fan to electric fan 342 miles into it. If anything, driving conditions were worse for this tank (colder mornings, road construction).

I don't know if weather is going to stay nice long enough to hope to crack 31 mpg, but we'll see... Hopefully a full tank with the tonneau and e-fan will pull me through.

[5speed5]

Latest tank was 30.4 mpg with tonneau and e-fan. The mornings were much colder for this tank than the last two tanks, and my truck sits outside all the time, so I'm thinking the 30.4 is great. Also had a new tank distance record of 573.6 miles.

The question is can I keep it over 30 mpg for the winter. I'm going to guess no without some new mods.

BTW, that makes for 4 tanks in a row over 29 mpg just to update the title of this thread...so it's not a fluke.

[UFO]

That's pretty good. Have you thought about installing an engine heater to keep warm-up time down?