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*note - I posted this thread in the "New Members" forum because I just created an account to ask this question but my post disappeared from the listings and says "Awaiting approval before being displayed publicly.". I tried asking the administrator what's up but no response so I'm going to try again by posting in this forum.

Hey all, I joined because I couldn't find a thread with this topic or someone else having this experience.

I have a 2012 Nissan Versa Hatchback that I bought a couple of months ago with low mileage -- around 30k miles -- and in excellent shape. It's a 1.8 S 4-speed automatic model. The advertised highway mpg is 32 mpg...three...two. Now get this:

If I do pure highway driving with cruise control on at around 75-80 mph to a city an hour away (I'm in the US midwest so relatively flat), do a few quick stops and return home for a total trip of around 112-115 miles, I'm easily getting above 50 mpg. To be specific, I've gotten 54 mpg, 52 mpg (one-way to isolate highway portion) and then 67 mpg today. Two of those data points are with the windows down. I noticed my fuel costs had decreased quite a bit for some time but didn't think to get actual data points until recently. I'm still in disbelief and have been wondering what colossally stupid math or mechanics error I must be making.

Process: I fill up before I start the trip, reset the trip odometer to zero and go. When I get back, I fill up. I then divide miles driven by gallons put in my car (I've also confirmed with google maps that my odometer isn't giving incorrect readings for distance traveled). That is all there is to it, right? right.

Here are the data points I've collected so far (which I've done the last 8 times I've filled up):

1. 112.0 mi / 2.067 gal = 54.184 mpg (highway)
2. 68.0 mi / 2.516 gal = 27.027 mpg (city)
3. 118.5 mi / 3.150 gal = 37.619 mpg (majority highway, some city)
4. 69.3 mi / 3.423 gal = 20.245 mpg (city)
5. 91.8 mi / 2.054 gal = 44.693 mpg (majority highway, some city)
6. 150.3 mi / 6.771 gal = 22.197 mpg (city)
7. 74.4 mi / 4.039 gal = 18.420 mpg (city)
8. 115.0 mi / 1.714 gal = 67.094 (highway)

As you can see, the relatively low city mpg averages out with the high highway mpg to settle into the high 30's/mid 40's if I mix highway and city driving.

Also, as another data point: I consistently use 87 grade fuel (with up to 10% ethanol) ever since I bought the car.

Some thoughts I've had trying to explain this:

a. Maybe the cruise control control system is really good at optimizing the engine characteristics at constant velocities? I exclusively use it when I'm on the highway and only interfere to brake or speed up to pass. Anyone else have a 2012 hatchback 4-speed and want to try some highway driving with exclusive cruise control to compare?

b. If this was an issue with my fuel meter giving incorrect readings and the fuel pump erroneously shutting off (I always fill to the top), I would have run out of gas randomly by now because I would be using more than I'm falsely replenishing.

So...is this normal? Is this secretly a fuel sipper extraordinaire that Nissan and folks in the know have been keeping quiet about? I, of course, have zero complaints; I just would like to get some perspective, lol

If this car had a hybrid design to make up for local-driving, this car would be giving the latest hybrids a serious run for their money. Anyway, thoughts and feedback appreciated, thanks!
 

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Now that you have provided your data, I see what may cause your really high gas mileage calculation: it is a very low volume of gas you use for each calculation, like 1 or 2 gallons. Gas station meters are not very precise, and any error of measurement applied to a smaller amount of gas will give large percent of a deviation. Try to use large volume of gas before you refill, like at least 4-5 gallons, and it all should be back to normal numbers in your calculations.

I happens to me, when I attempt to top off before a long trip, and fill up only about 1...2 gallons or so, the gas mileage is off, I do not consider it to be true.
 

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Now that you have provided your data, I see what may cause your really high gas mileage calculation: it is a very low volume of gas you use for each calculation, like 1 or 2 gallons. Gas station meters are not very precise, and any error of measurement applied to a smaller amount of gas will give large percent of a deviation. Try to use large volume of gas before you refill, like at least 4-5 gallons, and it all should be back to normal numbers in your calculations.

I happens to me, when I attempt to top off before a long trip, and fill up only about 1...2 gallons or so, the gas mileage is off, I do not consider it to be true.
Hmm, very interesting. Gas meters give out 3 decimal places, that's not accurate enough?

With that said, I still want to test out your suggestion. Now I'll have to think of an excuse to take a longer highway route to burn up 4-5 gallons and then see what I get purely highway mpg wise, hah.
 

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Gas meters give out 3 decimal places, that's not accurate enough?
Even if it could have been 20 decimals, it does not matter. You have no way to know how much gas actually got into your tank. Increasing number of gallons in the equation leads to minimizing percentage of error/tolerance of measuring actual gas pumped.
 

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You're not getting 50+ mpg...this cars mileage isn't particularly impressive. Your math is wrong by an out of wack odometer or fuel pump error.

Use full tanks. Or if you're insistent, run the car out of fuel, measure 1 gallon into a volumetric cylinder, and drive until it stops running.
 

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OP, even though you previously mentioned that your odometer matches Google maps distance, it would be helpful if you use a GPS unit to verify if your odometer mileage is true. Just to cover all bases... And use not a small distance like 1-2 miles, but something longer.
One of the reason your odometer reading may be off if you use tires with different circumference than OEM.
 

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It's possible to beat EPA ratings by several miles per gallon especially on the highway but, at 75-80 MPH it's not likely to be much over, if any. I have a '97 Ford Escort with a 2.0L 5 speed manual. It's ratings are 24 city, 34 highway, and 28 combined. With my type driving 40-55 MPH on rural roads with very little city driving I can usually average 31-33 MPG in local driving. Once on a highway trip on a cool summer day when I didn't need a/c and driving with the c/c set at 55 MPH I was able to squeeze 49.85 MPG out of it and have got between 40-45 MPG on several occasions. I suspect if I'd been driving 75-80 MPH that number would have dropped to below 40 MPG. There's a link in my signature to the fuel log for my '16 Versa. All those numbers are hand calculated and is every tank I've ran through it since I bought it in Feb. 2019. The dash computer in my Versa is usually about 4-6 MPG optimistic. It has a CVT and most of my driving in it is also 40-55 MPH on rural roads. I'm also very attentive to traffic and traffic light conditions. If a light 1/2 mile up the road is red I let off the gas and coast until the light changes green. I also keep a large buffer between me and any cars ahead so if I see their brake lights come on I can let off the gas and coast. Many times these two things prevent me from ever touching my brake pedal and wasting momentum and gas I've already burned. Unlike most people I always get at least 100K miles out of a set of brakes. I bought my '02 Escort in 2008 with about 80K miles on it; It now has about 205K. 125K miles later and it still has the same brake pads/shoes on it as the day I bought it. I checked the front pads earlier in the summer when I replaced the outer tie rod ends and they were about 1/2 worn. EPA ratings are also taken using 100% gasoline not 90% gasoline 10% ethanol that most of us burn. Straight gasoline has about 3% more energy than 90/10, but some people claim to get as much as 10% better economy using straight gasoline. I tried straight gas in one of my cars a couple years ago and saw no noticeable improvement in MPG, YMMV. One day I'm going to try a tank of straight gas in the Versa to see if it makes any difference in the accuracy of the dash computer. I was around and driving in the '80's when they first started selling 90/10 in this area instead of straight gasoline. When the change was made back all those years ago I don't remember seeing any significant difference in MPG between the two types of fuel. I bought my first car in 1977 and don't recall ever having one that I couldn't beat EPA ratings by at least a couple MPG if I drove carefully.
 

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Discussion Starter #10
@everyone who's replied - thanks for the all of the pov's and info and tips, I'm still working to get a longer trip in. When I get a couple more repeatable data points, I'll report back.
 
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