BAD gas mileage....

[Z71GUY]

Over the new years holiday, my G/F and I went to Michigan for a new years party with her sister.  On the way out, we were running late for the dinner up there, so I pulled out the old radar detector and crossed my fingers.  The slowest I drove was about 80mph...most of the time it was 85-95.  My truck was turning around 2200-2500 RPM's at this speed.  I'm thinking in the back of my head....I should get pretty good gas mileage on this run.  Well, I pulled into the gas station, filled her up.  Took a hair over 18 gallons...I checked my trip meter... 265 miles (one way - ALL highway).  This about 14.7mpg.  This is my normal around town MPG!?!?  On my way back, I drove around 75-80mph and got about 15.5 mpg.  I still think this is very low.  Keep in mind, most of this driving was done on the Ohio turnpike which is VERY flat...no hills at all.  Can anyone make sense of this?  I had my truck in the shop a few weeks ago getting some TSB work done and I had them update my tranny and engine software.  I know I used to get around 17-17.5mpg on shorter (40-50 mile) trips going 70mph before the visit to the dealer....

 

Do you think those high speeds are the problem with my mpg?  I was thinking the wind drag at those speeds would help contribute to this problem....

 

 

Eric

[RyanbabZ71]

last thankgsgiving (00) i drove from indiana to ohio (ohio turnpike).  gojng 70mph most of the way.  Got a little under 18mpg

 

My best ever

[GreenRado]

Eric:

 

Based on what you explained, I wouldn't expect this to be abnormal, albeit maybe on the low end of normal.

 

Without exception, I have never gotten as good cold weather mileage as warm weather.  Probably several factors involved there, including colder air temps (engine not running as efficiently), different fuel formulations for Winter vs Summer.  Certainly wind resistance will play an ever more increasing factor as you go faster.  Not implying angthing here, but even driving habits can vary the mileage a lot.  And, just for completeness, there could be something wrong, or just out of tune some (crappy gas, air filter dirty, plugs getting old, etc, etc).

 

My Winter HWY mileage, and I drive around 78 - 80 here in MI, on the interstates, is about 16 - 17 MPG, and 18 in Summer.  I have the 1/2 ton SB ext. 5.3 w/ 3.73 and topper (oops - old fart alert!!!).  Sorry didn't catch your engine/truck combo.

[Z71GUY]

Yep, I think you are right.  All of those factors probably helped produce the low MPG....temp, winter gas, wind, high speed...etc.  I only have 25k on the truck, so I would assume it does not need a tune up yet.  I'm not too worried about it now....I'll keep an eye on my local mileage to see how bad it is now.  

 

BTW, my setup is the 5.3 with 3.73's in the rear.  I do have a cover on the bed....I remember looking back and I could see the wind forcing the cover way down between the support beams....

 

 

Eric

[spham]

Same here It was 16.3 mpg on the moutain trip with only 2 guys. Yesterday I took my family out, 6 people, 80mph, 14.9 mpg Need that electric fan now!

[chevy4x4trucks]

Same here It was 16.3 mpg on the moutain trip with only 2 guys. Yesterday I took my family out, 6 people, 80mph, 14.9 mpg Need that electric fan now!

Let me know when you do the electric fan and how hard it was to do.  Some install pics would be great.

 

 

My MPG's are never really that good, but I account most of that to having to use reformulated gas.  When I was in MI I got about 4-5 mpg's more.  Partially due to using regular gas and also because it was a lot of freeway, although I did about 4-5 hrs of hard wheeling in 4hi on that tank.

[spham]

Will do. Incidentally I asked the same question in my corvette forum and got a couple of nice replies:

http://forums.corvetteforum.com/zerothread?id=210060

 

One guy chose not to go with the Flex-a-lite control because of having to insert the sensor into the radiator, so he went with the fan but got the control from another manufacture. I might consider this.

Another guy (vendor) has the same fan as the flex-a-lite but a little cheaper. You might want to post questions there too. The C3 corvette owners are very mechanically inclined as you would imagine

[EDZ Z71]

Over the holidays I took two trips over 200 miles each. I averaged about 16.2 mpg at about 75 mph. My Av has the 3.73 gears and only about 1200 miles at the start of these trips. I am totally satisfied. I didn`t know what to expect but this is acceptable. Maybe it will get better with some mileage on it.

[colosilverado]

I have a 5.3L ExtCab SB Z-71 and averaged 15.6 mpg on my recent trip of 375 miles, which included some autotrac/4 wheel  driving. Actually, I drove up over Cameron pass to Walden, Colo. and up to Independence Mountain, where I had the truck in a mix of auto, and 4-high. There was about 8" of powder on the mountain, so I had it in auto/4wheel almost the whole time I was on there,which was over an hour, and was on the throttle hard to keep momentum and buck some drifts.

 

Anyway, the whole trip was:

 

From Loveland to Greeley to pick up the wife's grandpa, which is highway driving at 65mph, then from Greeley to Ft. Collins (mostly all above 65mph), and then from Ft. Collins, over Cameron Pass (10,200'+) to Cowdrey, and on up to the top of Independence Mountain, which goes up to 9500', or so. Mix in some in-town driving in the various towns we went through, and that is a pretty decent picture. Of course, I reversed the trip going back home, all on a little over 23 gallons.

 

I was pretty impressed, overall. Again, my truck is a '99 Ext.Cab 1500, with the 5.3L, and no mods other than a topper/shell. There were 3 adults and 2 little tikes in the truck at the time.

 

I dunno, I think maybe your truck is a little off, but what do I know?

[jaslo]

I have the 4.8 V-8, 4X4 and just filled up and got 15.5. Even though its cold down here in MO. It just seems odd that the gas mileage keeps getting worse. Must be adding water to the gas too.  

[silverado man]

i dontl know what ive been getting since it got really cold havent filled up in a  gas station in about 3 weeks.  in the city have been averaging 14 and on the highway around 17.  

 

Hey Jaslo what part of MO are ya in im in K.C.

[jaslo]

I live around Jefferson City. Yeah but the 15.5 mpg is city and highway driving combined.

[NewbieZ71]

Speed kills........gas mileage.....my 5.3L w/3.73 got over 20mpg going from Albany NY to Canada border by going the speed limit of 65......god it kiled me to go that slow but wanted to see what the difference was......wanna save gas $$$?? Go slower....!

[DigUout]

No disrespect guys, but I'm always surprised by the MPG complaints on 1/2 and 3/4 ton trucks.  For all you get with a truck that size, good MPG is not one of them.  It's the trade-off.

[Z71GUY]

I realized that my MPG would not be very good in a 1/2 ton pickup.  But when my MPG goes from 17-18mpg on the highway to 14.5....I figured something was out of wack..either with my truck, gas or just the cold weather.

 

 

I've spoke with some other people about this and Newbie is right....speed does kill MPG in a pickup.  

 

 

Eric