2008 Cc Z71

sc4808 · March 30, 2009

I just thought that I would pass along a couple of expiriments that I did on my last long distance trip.

On the interstate @ 75MPH I average 17.9 MPG this has been checked multiple times during different times of the year and on different trips.

By simply adding a "low profile" hood protector, my Mileage dropped to 15.9MPG (I took the hood protector back off).

When using E85 my mileage drops to 14.2MPG.

Air Pressue and driving habits were the same on each of these test.

Truck is a 2008 Silverado K1500 with the 5.3L Al Flex Fuel and has 3.73 gears and stock wheels and tires. It is a Crew Cab LT

VR021302 · March 30, 2009

I just thought that I would pass along a couple of expiriments that I did on my last long distance trip.

On the interstate @ 75MPH I average 17.9 MPG this has been checked multiple times during different times of the year and on different trips.

By simply adding a "low profile" hood protector, my Mileage dropped to 15.9MPG (I took the hood protector back off).

When using E85 my mileage drops to 14.2MPG.

Air Pressue and driving habits were the same on each of these test.

Truck is a 2008 Silverado K1500 with the 5.3L Al Flex Fuel and has 3.73 gears and stock wheels and tires. It is a Crew Cab LT

I call on that. No way in hell a hood protector can cause a 2MPG difference. Unless is was concave and 6" tall, and with a head-wind.

VMax2007 · March 30, 2009

I call on that. No way in hell a hood protector can cause a 2MPG difference. Unless is was concave and 6" tall, and with a head-wind.

+1

Something else was contributing to that decrease.

asilverblazer · March 30, 2009

The hood deflector creating a large loss is interesting. I'd never have guessed it to be so great.

sc4808 · March 30, 2009

The hood deflector creating a large loss is interesting. I'd never have guessed it to be so great.

I left home and drove 300 miles with the deflector on (all interstate @ 75MPH) stopped took the delector off and filled up and drove another 300+ miles, the mileage on the DIC and checked manually both show the results I shared above.

If someone had told last week me what I just told you, I would have been doubtfull as well, but its the truth.

lvlagnum · March 30, 2009

Hello everyone.

Three months ago I traded in my old truck for a new one.

The old truck was 2003 Chev Silverado K1500 Extended Cab Z-71 5.3 4spd with I think 3.72 gears and completely stock. The mileage I was getting on that truck with 58,000KM on it was 12.4 L/100KM (19.0 MPG US) pure highway and 17.0 L/100KM (13.9 MPG US) pure city.

My new truck is a 2009 GMC Sierra K1500 Crew Cab Z-71 5.3 AFM Flex Fuel 6spd with 3.42 gears and completely stock. The mileage I'm getting on this truck is 10.0 L/100KM (23.5 MPG US) pure highway and 15.0 L/100KM (15.7 MPG US) pure city.

The 2003 Silverado didn't have a DIC so I was using the "fill before you leave and refill when you get there" method. The 2009 Sierra has a DIC so I used that for my mileage readings and have yet to confirm by the "fill before you leave and refill when you get there" method.

Keep in mind that with fuel prices as high as they are up here in Canada. I have learned to become a much more conservative driver. I used to cruise the highways (freeways) at 120 KPH and have now slowed down to 100 KPH (62 MPH). I have changed my city driving as well. My foot is a lot lighter than it used to be. I know for a fact that just slowing down from 120 KPH to 100 KPH saves me 20% in fuel.

I'm not sure if the variations in the gasoline blends we have up here makes much of a difference or not. We have the same octane ratings as you (I use 87 octane) but the ethanol content can range from 0-15% depending on where you buy it with 15% being the norm.

I know I've been a wee bit long winded and included a lot of information but I hope that you folks with similar trucks to mine will compare DICs (NO, not that one!) and see what mileage numbers you come up with.

Cheers, lvlagnum.

c4cruiser · March 30, 2009

Unless you did a long-term comparison between the DIC mileage figures and the manual calulation method, it could be that the DIC figures may be off. Over a period of time the DIC MPG values may be skewed. It's entirely possible for one truck to have accurate readouts and another to be off by some percentage. Sort of like "YMMV".

E85 will cause a drop in mileage and that's due to the nature of the fuel. The difference in mileage with and without the hood deflector sounds strange. But there could be other variables like driving into a wind, slightly different terrain, the fuel itself, air temp, humidity and even just a 2 or 3 MPH difference in cruise speed over a tank full.

MikeInCtown · March 30, 2009

The hood deflector creating a large loss is interesting. I'd never have guessed it to be so great.

I left home and drove 300 miles with the deflector on (all interstate @ 75MPH) stopped took the delector off and filled up and drove another 300+ miles, the mileage on the DIC and checked manually both show the results I shared above.

If someone had told last week me what I just told you, I would have been doubtfull as well, but its the truth.

Something else contributed to that decline. Temperature outside at the time of each run or various wind and or inclines that you went on or even direction of the highway. I put a deflector on my truck and noticed no change in any MPG. Then again I don't have active fuel management.

I've also noticed that different gas station nozzles do fill the truck up more than others. One station by me put in close to 20 gallons one day even though teh DIC said I used 18 point something. Another place usually cuts off a bit sooner. Unless you are filling up at the same pump and driving the same route you'll never know if the deflector actually did have any effect.

sc4808 · March 30, 2009

I usually run the hood protector this time of the year anyway because at 55MPH or less like around town there seems to be very little difference if any and the bugs this time of the year down south can be horrible. The biggest difference is definately at higher speeds say 70+ MPH Interstate driving.

I will check it again on my next trip to confirm my findings.

As a side note, on my 03 Sierra the difference on the interstate was less than 1 MPG usually around .7 or so. In many ways I think that it is slicker aerodynamicly than the new truck. I still own it as well but it has over 175K miles now.

The E85 result was expected, this fuel has less energy per gallon than gas.