Topic: Consumer Reports: Fuel Economy Overstated

[swishguy]

I so totally agree. i bought a 03 Vibe with 5 speed manual in 03. Window sticker claimed 47 mpg. hi-way. My best ever was 37 mpg...100% hi-way driving. I put on 51,000 km in 9 months & never broke 40 mpg.....even all hi-way summer driving!

[tpl]

Onearmed.  You are theoretically correct in that a Otto cycle gasoline engine is more efficient at wide open throttle as there are less pumping losses.... but that is very theoretical in real world conditions.

Swishguy: you may be a victim of the "exaggeration" of fuel econmoy figures as per the start of this thread.
However, have you tried driving all summer on the highway at 90kp/h with windows shut and a/c off with less than 1/2 tank of gas, tires at 40psi, one person in the car, 5w-30 synthetic oil in the engine and RedLine fluids in the diff and tranny....never going past the rpm at which the car does 90 in 5th in any gear and anticipating slowdowns and stops way ahead. If you try that you might get closer to 47mpg  but you wont like it much! 

[AVToller]

Interesting:

"Automakers conduct the government fuel-economy tests on a laboratory dynamometer. They can use hand-built prototype vehicles (italics added), within the EPA rules, to maximize miles per gallon in simulated city and highway driving. “Anybody taking a test, you’re going to figure out what the rules are and figure how to optimize your chances of passing that test,” says Reg Modlin, director of environmental affairs for Daimler-Chrysler. “So in that sense, yes, everyone attempts to put their best face on for the test.” "

This reminds me of the discussion about "cheating" on hp ratings, only it's even more extreme and ridiculous than the old SAE rules.

[onearmed]

For a turbo engine this is very true...you can give it a bit of gas and have the turbo at full boost (at low rpms) and it is actually alot more efficient.  The main point I was getting to is that the traffic on the highway is caused by bad merging and lane changes.  Also people holding up faster traffic even though the faster cars are breaking the law.   You eliminate the bad merging and lack of accelleration,stop and go traffic will be a thing of the past.  THerefore you increase everyones gas mileage ....  I love my illogical thinking.

Onearmed.  You are theoretically correct in that a Otto cycle gasoline engine is more efficient at wide open throttle as there are less pumping losses.... but that is very theoretical in real world conditions.

Swishguy: you may be a victim of the "exaggeration" of fuel econmoy figures as per the start of this thread.
However, have you tried driving all summer on the highway at 90kp/h with windows shut and a/c off with less than 1/2 tank of gas, tires at 40psi, one person in the car, 5w-30 synthetic oil in the engine and RedLine fluids in the diff and tranny....never going past the rpm at which the car does 90 in 5th in any gear and anticipating slowdowns and stops way ahead. If you try that you might get closer to 47mpg  but you wont like it much! 

[si]

Maybe transport canada should put a warning like

*figures under ideal conditions

or

*figures are hard to achieve

or

*figures are made up

[sterling]

i bought a 03 Vibe with 5 speed manual in 03. Window sticker claimed 47 mpg. hi-way. My best ever was 37 mpg...100% hi-way driving. I put on 51,000 km in 9 months & never broke 40 mpg.....even all hi-way summer driving!

Would it be safe to assume that your highway driving was at a higher speed than the 77kph used to come up with the Transport Canada highway rating?

[johngenx]

We have no problem meeting the Transport ratings.  But, it's possible to greatly exceed the consumptions numbers as well.  Hammer the pedal at every light (as MOST drivers I see do), leave the car idling as you go into the store (again, many do) and haul around a trunk full of junk.

Little things also add up.  Out of tune, 18psi tires and so on can add a L/100km or two.  Before you know it, something rated at 11L/100kms is getting 14 or 15L/100kms.

Our C230 is rated at 9.5 city and 7.2 highway.  City driving I pretty much match that number.  Highway I can get 6.5 if I stick to 100km/h and try to stay off camper-choked routes.  Typically, I can easily get in the low 7's.  I can get in the 8's if I really hammer along.  So, I can easily get 25% worse highway mileage by eeping the speedo on the other side of 140.  Last time I came back from Jasper on highway 16, I was sitting in the right lane at 145 and being passed prety consistently by folks in big Dodge pick-ups and large SUV's.  If I'm increasing my consumption by 25% or more in my quite-aerodynamic sedan by doing 145, I can imagine how much extra gas the V-8 brick-like SUV is sucking back.

[eddy4]

I dont think fuel economy is the first thing most enthusiasts look at when they purchase a vehicle .

Use your head, big motor less economy , heavy vehicle less economy , drive enthusiasticaly less economy ... ....