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

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

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?

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.

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.

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?

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. :)

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.

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. :)

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

With an engine heater, you might see 32......

I hadn't really thought about it. Not a bad idea. How difficult are they to install?
-Tim

depends on the vehicle and motor. If you can get to a frost plug without taking anything apart it is much easier. Just drain your coolant, punch out a plug and put your heater in. Just make sure you knock out a plug with enough clearance behind it for the heater. If you knock out the wrong one, just put in a new one and try another.:thumbup: Piece of cake

nice 4x4 milage, i was able to get one 30+ mpg tank out of my old 4x4.... but that is dealin with 1500-2000 foot elevation change.

if i remember right, the block heather for the colorado/canyon only works under certain ambient temperatures. something like 15* and below, don't quote me though, just a shot in the dark on the temp.

I have a adhesive pad heater that gets applied to the oil pan. I would be willing to sell it, as it is still in the packaging. I have a really nice garage and really dont need it. Here is one that is very similar:
Online Store - dieselproducts.com

I would be willing to sell it and ship for $60.

I haven't posted in a while, but I've been getting (relatively) awful gas mileage. Two
tanks under 28.5 mpg (colder weather and winter gas) and then I stopped using EOC (didn't feel safe now that it's dark and cold when I drive to and from work), so my mpg went down into the 24s. This next tank is going to be even worse as we've had record low temps and enough snow to require engaging 4WD for a few of my commutes. My truck lives outside, so on those bitter cold mornings, the truck barely gets to operating temp by the time I get to work 9 miles later. I'll probably be lucky to get 23 mpg.

I have not been driving the truck the last few weeks. My fuel pressure regulator went to pieces. I was getting ~25 even with the cold temps and short trips. I am hoping to get it fixed soon.

That's very good mileage for a full-size in winter. My latest tank wasn't as bad as I was thinking. I got 23.57 mpg. Hopefully, I've bottomed out with that, but if the weather keeps up like it has been, the worst may be yet to come.

In regards to you mentioning that EOCing wasn't great in this truck due to coasting-- Even in 2wd the front differential and driveshaft still spin. Look up for your transfer case if this is OK, but consider pulling the front driveshaft during summer time to remove some drivetrain drag. Having to spin that driveshaft with the gearing reversed (large ring gear spinning the small pinion) is sure to cause a good bit of drag.

Thanks, that's a good idea. I'll definitely look into that in the late spring.

One of the front axle shafts may have a disconnect in it. My Suburban has one. This does not prevent the spider gears from spinning, but it does prevent the front drive shaft from spinning. Coast down will be greatly affected because it's an aerodynamic pig (improved a bit by you).

The screwed up way GM does some computer diagnostics is the problem with the block heaters. If it detects a "cold start situation", which on some models involves the ignition being off for more than 10 hours, it will set off a CEL code. It is harmless. To prevent these CEL from coming on, they put a thermostat in the heater cord, that prevents operation above 0°F. Every other manufacture figured it out, just not GM. This started in 2004 or 2005. You may be able to use one all year long, just check. That said Katz supposedly makes two for my vehicle, one with the thermostat & one without. I haven't investigated further.

Has anyone ever put the stick on pad heaters onto transmissions & differentials (that don't live above the 48th parallel)?

Good luck.

Don