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Sudden Decreased Fuel Mileage!

Actually, I meant to say “1/2 empty or less”, as I don’t fill up until I’d down to a few gallons. Saves gas and time, as both are used filling up the tank and driving to the pumps.

@the_same_mountainbik
@BillRussell

Thanks for not just telling the WHAT but the WHY as well. I’m far more willing to listen to advice when it explains to me why I’m doing something wrong. Not just telling me to do something right or don’t do it at all. That does nothing for me and I’d rather someone not even respond with information as useless at that is.

Me too.
Thanks for the compliment. :relaxed:

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On the $1000+ estimate they told you they would clean MAF and replace an air filter.
Clogged air filter can easily rob you off 5% of MPG, cheap and easy to replace on your own.
You could also consider getting some mid-range injector cleaner into a tank of gas and see it it improves.

On another side, as you moved, did you change you commute time or driving habits?

I have usually ran off of the top half of my fuel tank for many decades. I can’t remember the last time I requested an amount other than a fill-up. There are so many possible variables in OPs somewhat reduced fuel mileage complaint. E10 will be about a 4% reduction just to start with.

On the $1000+ estimate they told you they would clean MAF and replace an air filter.
Clogged air filter can easily rob you off 5% of MPG, cheap and easy to replace on your own.
You could also consider getting some mid-range injector cleaner into a tank of gas and see it it improves.

On another side, as you moved, did you change you commute time or driving habits?

One of my major variables. Also switching from Southern California non Winter blend fuel to Washington state Winter blend. In Oregon I suffer a 3 to 4mpg loss on Winter blend with of course possible additional factors. Does the Nissan Versa not have an average mpg display? My Kia’s (checked manually) is very accurate.

[quote=“andriy.fomenko, post:24, topic:100867, full:true”]
Clogged air filter can easily rob you off 5% of MPG, cheap and easy to replace on your own.
[/quote]While I agree it needs to be changed, a dirty air filter has almost no effect on fuel economy in a fuel-injected car.

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The reason for not running the tank empty is that the fuel pump is cooled by the fuel it sits in. When the fuel pump is not sitting in fuel, it runs hot, which leads to premature wear, which ends up costing money. Because of this reason, I try to fill up when I have 1/4 tank left.

That air filter doesn’t look too bad to me.
Here’s a study on the effect of air filter restriction on fuel afficiency:

great report!

as I’m reading it, some info is worth mentioning:

All of these functions are to be met for the service life of the filter without allowing engine performance
to be affected.5
In light- and medium-duty applications, the service life is normally defined by
accumulated mileage. However, it is very common for over-servicing to occur in these applications due to
a lack of understanding of how optimum air filter efficiency is achieved.5,6
The standard recommended
service life for an air filter in light- and medium-duty applications, during normal driving conditions, is
about 30,000 miles.5–7
It is common, however, for servicing to occur when the filter appears dirty. Engine
air filters are designed to actually increase their efficiency by using this initial layer of dust as an added
filter layer. Initial filter efficiency is usually approximately 98% but increases to more than 99% by the
end of the service life of the filter.7,8
Therefore, changing an air filter before the useful service life is
achieved can result in premature engine wear.

Then they proceed to actual results where air restriction reduces performance to extent driver would “feel” it, but, surprisingly, not affecting MPG!
learning something new every day :slight_smile:

Results show that clogging the air filter has no significant effect on the fuel economy of the newer
vehicles (all fuel injected with closed-loop control and one equipped with MDS). The engine control
systems were able to maintain the desired AFR regardless of intake restrictions, and therefore fuel
consumption was not increased. The carbureted engine did show a decrease in fuel economy with
increasing restriction. However, the level of restriction required to cause a substantial (10–15%) decrease
in fuel economy (such as that cited in the literature3,4
) was so severe that the vehicle was almost
undrivable. Acceleration performance on all vehicles was improved with a clean air filter.

How fast your gauge drops is not the way to determine your mileage. Fill your car normally. Zero your trip odometer. Next time you fill up, divide the miles on the trip odometer by the number of gallons you put in. That is your mileage. Repeat the process 5 times and you will know what kind of mileage you are getting.

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+1
In addition to this good advice and all of the other pieces of good advice, I would like to remind the OP that a car’s gas gauge is not a laboratory-grade measuring device, and should only be considered to provide an approximation of the amount of gas remaining in the tank.

And, that is if it is functioning properly. If the gas gauge has become less accurate than it was when the car left the factory, then assuming that the reading on that gauge represents how much gas has actually been used could be…a very inaccurate assumption.