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Comments
there are various advantages to electric fans or electric water pumps or electric power steering pumps. i think a big reason for the electric fans is especially so the coolant/etc can be chilled somewhat after the engine has been turned off, to avoid "heat soak" .
another reason for electric accessories is that it does save some pointless energy/movement/wear when the engine is at high-rpm. i bet it does improve mpg by a teeny tiny bit but i'd be surprised if that were a primary reason for using electric fans. also in a Tahoe/Suburban, i doubt that would make a noticeable/measurable/appreciable mpg difference!
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I can assure you that the engine uses much less energy turning an alternator pulley than turning a large fan blade. You are burning fuel to run that alternator for everything else electrical on the vehicle, so might as well have it power the cooling fans. As you mentioned the fans then can also be used after the engine is shut off for cooldown. And the noise level from the engine compartment is less with the electric fan system. And by having several mounted around the radiator core you can achieve better air flow for better cooling as opposed to one large fan. Back in my drag racing days one of the easiest ways to gain measurable horsepower was to unhook the belts for the power steering/AC and/or alternator/generator for the run down the 1/4 mile track. Some racers would even unhook the fan belt when firing up on the start line, then immediately shutting down the engine at the finish line so as not to overheat the engine since there was no water pump action or fan blade cooling with the belts off. No totally free lunch with the electric fans....but a pretty good discount.
My experience over the last few vehicles that I've owned has been with reasonable driving techniques, I could get at or better than the EPA values. Not so with my '07 LTZ. Granted I only have 2K mi, so hoping will improve but to date it's about 12/16 mpg. Not even close to the 16/21 EPA estimate.
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My original reply was to Magyver who said he had installed a lightweight Flex-fan in his '01 model and his gas mileage had increased. That is how the mention of the new GM electric fans on '06 models came into play. I too can beat EPA estimates by driving in a reasonable manner with my '06 Suburban. Seems to me the '07 should do even better.....maybe your mileage will increase as the engine gets a few more miles on it.
Your original statement addressed to the original poster was:
You say the EPA figures are not absolute and that you have had vehicles that do better and some that do worse. How then can you use them as relative values? Relative to what?
My point was that there is intrinsic error in any measurement so the EPA figures should really be published as such and such plus or minus whatever, i.e. there should be a standard deviation attached to those numbers. This, I believe, is what the original poster meant when he said the figures are not absolute.
Even so, we can still use the figures for comparison between the ratings attached to different vehicles meaning that if the rating is higher for vehicle A than for vehicle B then, on average, type A vehicles will get better mileage than type B vehicles. Of course, in any give pairing of vehicles from each class that may not be the case.
Hope that helps!
tidester, host
Thanks Tidester.
I also went further and said that for 99% of drivers, if they aren't acheiving the EPA numbers for vehicle B, then they also won't acheive them for vehicle A.
1.The Suburban weighs 400 lbs. more than the Tahoe. That extra weight increases fuel consumption.
2.Overinflated tires do not improve fuel economy...but underinlated tires will reduce fuel economy.
3. Careful driving...yeah well, safe is good...but it does not change the physics of a 6100 lb. load being pushed by a 5.3L gasoline engine.
4.The air filter element on all Tahoes and Suburbans is an excellent fluted paper element design. It's surface area is designed by GM to be very large and it does not saturate very easy. Because pressure drop is so low and air flow so unrestricted...this is not a determining factor for these two vehicles.
5.Drag racing from stoplites...we don't do that anymore.
6.Tuning the 5.3L is limited to very few things that can be be tuned. The on-board computer and sensors accurately control spark timing, air/fuel ratios and monitor valve timing and cam angles. Modern spark plug technology limits the electrode wear on the plug tips so that they last a long time. So what is it that you are tuning?
I've have lots of tanks better than that percentage. My van gets 17/24 EPA and my lifetime is 21.4. The average (mean?) of 17/24 is 20.5 so I'm getting 104% of the EPA ratings over ~112,000 miles. I'd probably be doing even better if my tires weren't 3 pounds off and if I'd replace the original plugs.
steve_, "Hyundai Tucson: MPG - Real World Numbers" #29, 29 Jul 2006 5:04 pm
I don't really care if you believe anyone here or not so long as you keep it civil. But it's a nice chance for me to give Tides some math to double check. :-)
The average is a little more complicated than just taking the straight average of the two EPA numbers. The issue ultimately is how many gallons it takes to drive a given number of miles.
I'll just point out that the actual figures depend on how your miles are split between city and highway. Even then there is one more complication: Do we use a DISTANCE based split or a TIME based split?
E.g., when someone says his/her driving is split 50-50 between city and highway do they mean equal miles traveled on city and highway roads or do they mean the time spent on them is split 50-50? They can give significantly different answers for your "average!"
In your example, let's assume a 50-50 split between city and highway. These are the results:
50-50 DISTANCE split: The EPA "average" would be 19.9 mpg and NOT the 20.5 you got using the straight average so you would be doing better than EPA.
on the other hand ...
50-50 TIME split: Here we need to know what "city speed" and "highway speed" are. I chose 30 mph for city and 70 mph for highway for your case. The EPA "average" turns out to be 21.36 mpg - which puts you spot on with your 21.4 mpg figure!! (Double exlamations because I was truly surprised by the result even if it may be fortuitous.)
I think most people probably mean a TIME split when they think about how their driving is divided between city and highway. Driving at twice the speed for the same period of time you cover twice the distance of driving at the slower speed but you don't use twice the gas. This accounts for the discrepency with the DISTANCE and TIME calculations.
At some point I may post details in my CarSpace for anyone interested.
tidester, host
Rockman59 and Oniscus may have read the old Hybrids and Hypermiling - A Help or a Hazard? discussion and learned a few tricks too. :shades:
If 16-21 MPG averages were achievable we would see them. 18.5 MPG...which is the mid-point of that range...is too far from real world numbers to be a simple error. What am I implying? I'm not implying. I'm stating that reality is not 16-21 MPG. Those numbers are wishful thinking for some...and possibly worse for others.
Top 10 Tips for Improving Your Fuel Economy
The various Consumer Ratings & Reviews would be another source; many of those owners report (or complain about their mpg).
Unfortunately many people don't post on forums unless they have a problem, and most people don't keep track of their mileage.
So, it all boils down to YMMV. :shades:
The truth isn't exactly black and white but owners have been irked for some time and, as Steve already pointed out, change is happening.
tidester, host
Why does it take federal legislative action to correct a product performance claim problem? Why has U.S. EPA not changed it's methods of estimating fuel ecomnomy for 21 years? Why did it take a mandate in the U.S. Energy Policy Act of 2005 to effect change in fuel economy estimates?
Section 774 of EPACT 2005 instructs the EPA to create new fuel economy measurements that more accurately reflect today’s speed limits, city driving conditions and the use of air conditioning and other fuel depleting features.
Was it reasonable to use 45 miles per hour as the representative highway speed for testing for 21 years?
Are city driving conditions in Los Angeles representative of most city driving conditions in our country?
Do we not use A/C to survive the heat and humidity in places like the south half of the U.S.?
Oh yeah...don't take my word for it.
From te U.S. Senate Committe on Energy and Natural Resources...
Chairman's statement:
“The EPA hasn’t updated fuel economy estimates since 1985. We instructed the EPA to update their fuel economy estimates after hearing from frustrated and disappointed consumers who weren’t getting the mileage from their vehicles that advertisements had led them to expect.
“I consider this provision in the energy bill one of the most potent consumer protections in the bill. It will literally influence how American consumers spend tens of thousands of dollars. Buying a vehicle is one of the most expensive choices a family will make. With gasoline hovering at $2.50 a gallon, fuel economy estimates play a huge role in that choice. I am pleased that the EPA is moving swiftly to implement this provision in the energy bill.”
We can make good choices...if we know the truth.
(a) YMMV.
(b) the EPA system is flawed.
(c) the EPA system is being ovehauled.
(d) the EPA is a federal agency and, by definition, requires federal action to implement change.
and
(e) we appreciate members reporting their mileage here for comparison and for providing real world experience to those considering the purchase of these vehicles.
I think we've taken this as far as we can here.
tidester, host
The "guidelines of change" are going to reduce the mileage estimates we read on the window sticker. The guidelines as suggested will make them go down:
City - 10 - 20 %
Highway - 5 - 15 %
If the two percentages on the high side are used for the Tahoe -
16 - 21 MPG becomes 12.8 - 17.8 MPG
The mid-point goes from 18.5 MPG to 15.3 MPG. ( Which I personally believe is much closer to the truth.)
Picture a salesman standing next to two Tahoes...down the road...say ~18 mos. or so. His job is to explain why the 2007 model Tahoe is rated 16-21 MPG...and the exact same model parked next to it in the 2008 model year is now rated 12.8 - 17.8 MPG.
tidester, host
CITY - 9 MPG
Overall - 13 MPG
My wife and I are doin' pretty good at 14.5 MPG O/A.
1) How many of you regularly carry 5 or more people plus a full load of cargo, or regularly tow large trailers/campers/boats/ect.?
I take note of the big SUV's I see on the roadway, and the vast majority are carrying only the driver, and are not loaded down with cargo or a big trailer. Which begs the question: Why do people need or want these vehicles???
2)For those complaining about fuel economy, what did you expect from such a vehicle? Does it really matter whether you're averaging 14 MPG instead of 18 MPG?
14 MPG and 18 MPG are BOTH dismally low fuel economy numbers.
Maybe for the times you don't see them, when they are pulling a boat, camper or hauling their 4 friends to the deer shack or the mall.
18's a lot better than 14.
That's not your job as moderator/host... why interfere? Let the forum members respond to mattgg1's question.
There's plenty of more appropriate places for that thread, like the Why GM, Chrysler and Ford wont build high mileage cars and trucks?? discussion.
Anyone like to report on their mileage?
Full load of cargo...oh yeah...done that many times. Our Tahoe will haul stuff. Example: Helped neighbor build wood fence after Katrina. Hauled all the lumber, concrete, hatdware and tools needed to get er' done. Multiple loads. Well over 5 tons of stuff. His Honda Accord could not handle it.
We tow a fishing boat...not as often as I'd like.
We tow rental trailers...like 12' x 6' U-Haul trailers for moving & hauling things like mulch, landscape trees/shrubs/plants.
Hunting and fishing...lotsa' gear to take down to the shore...or to the hunting lease...works well.
Take the dog to the park...80 lb. lab...he jumps in.
Fuel economy - expected 16 to 21 MPG. Mid-point 18.5. Yes, it does matter.
Very appropriate for this discussion, eh?.
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Why would anyone want to do that? I shared my mpg numbers with this forum and our mileage expert RSpencer says it is not possible. Obviously he knows exactly the mpg that every one of the 150,000+ '06 Suburbans are getting. No need for anyone else to report mpg. Especially if they are getting anything above what RSpencer claims is impossible. He will be sure to let us know that any Suburban that gets better mileage than his must be owned by someone who works for GM. If anyone else decides to share their above average mpg numbers please attach an affidavit with your post stating that you are not an employee of GM so RSpencer can sleep tonight.
Yes, some people here get their undies in a bundle.
As to the mattgg1, here's some answers:
1: most of the time. Three kids, business gear (60-inch cases), camper, rental construction equipment...and even space to to take the grandparents/friends out to dinner along with the kids. Went for a bike trip recently and had five people and five bikes in the back. Try that in a Yaris. Oh, and it has 4wd, not bad in No. Minnesota.
Yes, a third of the time I'll drive it empty all by myself. I did tonight, to a lumberyard, empty. Of course, on the way home I had the back end half filled with building material.
2: I expect to get decent mpg from this vehicle..it's certainly not unreasonable to expect.
I find a great deal of misinformation out in the world regarding actual mpg. I was out at a dinner party at a chic place and a guy with the trendy specs and the very important worries about global warming made some 'jokes' about big SUVs getting 9 mpg. I didn't correct him. The blowhard eventually ran out of energy....
I've got a 2002 suburban with a 5.3. When I lived in California and had only warm weather and no ethanol in the gas I NEVER got below 15 mpg, ever. Best was 20 mpg on a long highway trip, eaaaasy on the throttle. I now live in MN where everythign is 15 percent ethanol (worse mpg) and cold for four/five months. I've also got aftermarket aggressive tread tires that cut mpg, and now I can get at best 18 but I rarely drop below 14. Stop and go all winter at zero degrees and I'm at 12. But in the same weather my dad's Toyota Highlander never gets better than 4 mpg more. We drive on a trip, he gets 23, I get 19. In winter, he gets 18, I get 14. Oh, and my transmision works great, his doesn't (different topic....).
So, no, smartyasspants, my big SUV doesn't get 9 mpg, and I routinely get EPA ratings....It's not great mpg, but it doesn't stink as badly as people think.
Off topic a bit, but I'm curious too about the 2007 5.3 mpg....I bought a Pontiac grand prix gxp earlier this year with a 5.3 v8 and in 4 cyl. mode I've nursed a true 29 mpg out of it on a long trip....not bad for 303 hp. The cylinder cut-down technology works...
But the majority of full-size SUV owners do not fit into any of these categories, and those that do don't use the vehicles for thier intended purpose most of the time.
For instance, splatsterhound drives his gas-guzzler around by himself (with no cargo or trailer) 33% of the time. I would guess another 33% it is just him/wife and kids, with no cargo/trailer. Probably another 20%-30% is carrying people & cargo that could fit in a more fuel efficient vehicle.
So, 90+% of the time, he could be getting 32 MPG in an Accord, which seats five and has adequate trunk space. Instead, he gets half that mileage, for the few times he needs to haul a few 2X's or the grandparents to dinner. Makes sense to me!
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Replying to: dsquare (Jul 09, 2006 6:58 pm)
My 07 4wd LTZ is getting 12.5 MPG Which sucks
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Your LTZ has full-time 4 wheel drive and as I recall you have the bigger 6.0 V-8 and the 3.73 rear axle. With the 20" rims and wide tires your mpg will be much less than the LS and LT models with the 5.3 V-8. My 2006 has the 5.3 engine, 3.42 rear axle and 16" wheels. At 65 mph I am getting 22mpg. At 60 mph I get 23mpg. City driving is around 18 mpg. This is in 2 wheel drive, AC not on, and no stop lite drag racing.
Better yet at 18 MPG city...on July 11. Wow...how do u get that on your Suburban?
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Sorry...that was a typo.
Best ever was 3 tanks in a row in Yellowstone. 22mpg average. I used the same pump each of the three days.
Nearly all the gas we use is 10% ethanol. Cold weather does impact MPG too. In the winter the mpg drops to about 13 for city use.
As a side note: My Dad's Silverado 4x4 with the 5.3 gets 20mpg on the highway (interstate trips).
EPA estimates or above.
As to why you see big SUVs with one person in them... My wife drive the Tahoe to work. We can't afford to have a third car. The cost of a $14K Civic buys a lot of gas for the Tahoe. The extra insurance alone for a third car buys a lot of gas. On top of that some Civic drivers get in 25mpg range for city driving.
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Almost newer anybody else in the car but me driving it.
Why have it? I spend 4 days of a week on road. Need safe and comfortable vehicle to drive.
Had a Crown Victoria, which was decent but lost engine due to spark plug blow-out (big Ford engine problem) and had to get something that I can trust. As I want to buy locally made vehicle which is big for safety the options are not too many. Also, riding as a passenger in a similar vehicle made me turn my head as I was also thinking why have one before.
I have driven a lot of different vehicles and I must say that from all of them Tahoe LT that I have has the best seat I have ever had in a car.
And the whole thing rides so easy that I can drive for hours without getting tired stopping for only gas.
But, you know, before you own one you don't know what you are missing.
--Arrie--
It almost seems like in normal mode the transmission has more drag that with towing mode on.
Only 'bad' thing about the towing mode is that it won't shift to highest gear if your speed is below about 58 mph.
I saw a discussion about this item in somewhere else in these forums but can't remember where but that is why went to try it and it really seems like with tow mode on MPG goes up.
Perhaps I have an individual problem...?
--Arrie--
It's fun repeatedly having to justify what we drive for those without a clue though. :mad: