ReservoirD

There has been much ado on this board about the mileage of the 2002 Maxima, especially the manual transmission 6-speed (or perhaps that's just my bias). In this post you will find text from the EPA's website http://www.fueleconomy.gov/feg/info.shtml that provides an overview of the testing procedure. I found it to be very good reading.

My question is this: is the EPA estimate of 21/28 (20/26 for the automatic) accurate and/or reasonable? And if it's not, how did the estimate come about?

In big fat numbers on the sticker of all new cars is the EPA's fuel economy estimate, which on the 2002 Maxima 6-spd is 21 mpg city, 28 mpg highway. Small print under the city number says "Actual Mileage will vary with options, driving conditions, driving habits and vehicle's conditions. Results reported to the EPA indicate that the majority of vehicles with these estimates will achieve between 17 and 25 mpg in the city and between 23 and 33 mpg on the highway."

Does that explain the poor mileage that most of us are reporting here? Could it be that the satisfied owners are quiet instead of squeaking their wheels? I don't think so. Read the statement carefully; it says that the variables that will have an impact on mileage are "options, driving conditions, driving habits and vehicle's conditions," not sample variation. This statement does not mean that with two identical Maximas, driven exactly the same way, we shouldn't be surprised if one got 17 mpg and the other 25 mpg. Would Nissan's V6 engines be so highly and universally praised if there was this much variability in their performance?

It is possible that everybody posting here with poor mileage numbers is driving the car hard and therefore getting poorer mileage. Well, almost possible. I've been driving like my dad trying to get better mileage, and have had only marginal success. Personally, I beleive either there is something wrong with my car, or else the car just can't achieve the mileage in the EPA estimates. Since my dealer told me there's nothing wrong with my car, and dealers never lie and are never wrong, I have to assume that the Maxima is not capable of the sticker mileage.

So I started looking into the estimate. Here is the testing procedure, found on the EPA site http://www.fueleconomy.gov/feg/info.shtml:

"How are fuel economy estimates obtained?

"The fuel economy estimates are based on results of tests required by the U.S. Environmental Protection Agency (EPA). These tests are used to certify that vehicles meet the Federal emissions and fuel economy standards. Manufacturers test pre-production prototypes of the new vehicle models and submit the test results to EPA. . EPA re-tests about 10% of the tested vehicles to confirm manufacturer's results in EPA's lab. The vehicles are driven by a professional driver under controlled laboratory conditions, on an instrument similar to a treadmill. These procedures ensure that each vehicle is tested under identical conditions; therefore, the results can be compared with confidence.

"There are two different fuel economy estimates for each vehicle in the Fuel Economy Guide, one for city driving and one for highway driving. To generate these two estimates, separate tests are used to represent typical everyday driving in a city and in a rural setting. Two kinds of engine starts are used: the cold start, which is similar to starting a car in the morning after it has been parked all night; and the hot start, similar to restarting a vehicle after it has been warmed up, driven, and stopped for a short time.

"The test used to determine the city fuel economy estimate simulates an 11-mile, stop-and-go trip with an average speed of 20 miles per hour (mph). The trip takes 31 minutes and has 23 stops. About 18 percent of the time is spent idling, as in waiting at traffic lights or in rush hour traffic. The maximum speed is 56 mph. The engine is initially started after being parked overnight. Vehicles are tested at 68 F to 86 F ambient temperature.

"The test to determine the highway fuel economy estimate represents a mixture of "non-city" driving. Segments corresponding to different kinds of rural roads and interstate highways are included. The test simulates a 10-mile trip and averages 48 mph. The maximum speed is 60 mph. The test is run with the engine warmed up and has little idling time and no stops (except at the end of the test).

"Note: To make the numbers in the Fuel Economy Guide more useful for consumers, EPA adjusts these laboratory test results to account for the difference between controlled laboratory conditions and actual driving on the road. The laboratory fuel economy results are adjusted downward to arrive at the estimates in the Fuel Economy Guide and on the labels seen on new cars, light trucks, and vans. The city estimate is lowered by 10% and the highway estimate by 22% from the laboratory test results. Experience has proven that these adjustments make the mileage estimates in the Fuel Economy Guide correspond more closely to the actual fuel economy realized by the average driver."

So according to the numbers and the last paragraph, the 6-speed Max they tested got about 23.3 MPG city and about 35.9 MPG highway. Is there anybody here with a 2k2 6-speed that could get 23 MPG on a cold-engine-start 11-mile trip with 23 stops? Has anybody ever come close to 35.9 mpg highway? I don't think I could make these things happen in my car, even if I lugged the hell out of the engine the whole time. And you would be beating your engine up if you drove 60mph in 6th - my car's tach reads 1900rpm at that speed.

Most likely, Nissan provided the numbers to the EPA and they went by unquestioned. I could not discern from the arcane data charts whether they used 87 (the recommended fuel) or higher octane fuel to perform the tests.

Now, in the interests of full disclosure, another part of the same page:

"Why is the fuel economy of my car different from the estimates in the fuel economy guide?

"No test can simulate all possible combinations of conditions, climate, driver behavior, and car care habits. Actual mileage depends on how, when, and where the vehicle is driven. EPA has found that the mpg obtained by most drivers will be within a few mpg of the estimates in this booklet. To find out what you can do to improve the fuel economy of your car look at Driving More Efficiently and Keeping Your Car in Shape."

This sounds like it gives Nissan an out, because even I am within "a few mpg of the estimate." However, if they fudged their numbers, this will provide slim protection for them.

I have inquiries in with the EPA asking for more information, and will of course share anything I find.

Green 2kSE

You might be surprised at what mileage you would get if you drive at 50mph on the highway. I get close to 30mpg even with a loaded car at 70mph average speed on the highway, so 15% increase at 50mph would be conceivable. BTW, you would not be lugging your engine at 1900rpm in 6th gear if you are just maintaining your speed, I would love to have your extra gear. As far as the city mileage goes, it will vary alot between seasons, metros (RFG, traffic) and drivers. FYI, I get the advertised 21mpg consistently and consider that OK for the class of car I'm driving.

ReservoirD

But Greenie - If your user name is any indicater, you've got a 2000 rather than a 2002, right? Different engine altogether and not in the group I'm talking about.

And how 'bout this; according to the EPA, the 2000 with the 3.0L engine and 5-spd got worse mileage than the 2002 with the 3.5L and 6-spd.; the 2000 auto is listed at 20/28 (compared with 20/26 now), but the manual at 21/27 (compared to 21/28 now). Interesting to me that the extra juice doesn't seem to cost more in city driving than the changed gearing seems to gain.

Virus

iTrader: (1)

Your test is scued. While I never meet the EPA mileage in the City I usually exceed it on the highway. I get between 30-31mpg with my 2k2 auto on the highway.

ReservoirD

I'm guessing you mean the poll. Yah, I thought about that, but the site only allows five choices, so I did the best I could! So, decide how much of your driving is city vs highway and make a choice.

Maybe another time I'll put out more specific polls.