Gas mileage for 2000 Civic Si

I am wondering what kind of gas mileage you are getting with your 2000
Civic Si?

The EPA rating says 25 - 31. I have always been filling the tank with
Octane 93 gasoline.

I have been receiving around 28 - 29 MPG when driving consecutively on
highway at around 75 - 80 MPH. For mixed city and highway commuting,
the car gives around 25 - 26 MPG. I also experimented with AC on and
off, and found that it makes very little difference.

Recently, the gas mileage of the car deteriorated to 22 - 24 MPG. The
only difference would be that a couple of weeks ago I visited a
no-name gas station for a fill-up instead of the same few name brand
gas stations I normally use. The gas gave me significantly lower gas
mileage, and I ran out of gas on highway because I wasn't expecting so
few miles out of a full tank. Fortunately, it was only half a mile
from home. I walked to the gas station nearby, brought back a can of
gas and filled the tank. The car started fine. Ever since then, I have
run through a couple tanks of good gas. But the gas mileage never
recovered.

I am wondering if this is a problem I should worry about. Should I use
gas treatment? Fuel injector cleaner? Replacing gas filters? The last
time when I applied carburator cleaner to my other car, the fuel
economy actually went significantly worse! That's why I would hesitate
to use it on this car.

Any advice would be appreciated. Thank you.

 

One idea:

A malfunctioning PCV valve can cause gas mileage to decrease. Ever checked
yours?

I replaced my 1991 Civic's PCV valve for the first time at about 140k miles, 12
years. It was totally blocked with waxy carbon buildup and was way overdue for
at least a good cleaning. The gas mileage shot up, increasing over 10%
consistently.

In the future, I plan to replace my PCV valve at 60k miles, four years, or
whenever a check indicates it's not working. What's the mileage on your car?

An OEM PCV valve (vs. non-OEM) seems to make a difference, from reports here.
The OEM is inexpensive enough (around $20) to be worth it.

 

A friend of mine also pointed out that PCV valve and the fuel filter
may need to be replaced. The car is 4 years old with 37 K miles.

 

================

About the fuel filter, unless a person drives 30 miles of dirt road a
day, changing the fuel filter seems to be a waste of money, at least at
low mileage. Some use the term 'lifetime' to describe the fuel filters
on newer models.

A tank of gasohol might clean up the injectors, or a can of Techron
injector cleaner won't hurt, but bad gas can certainly make you car run
badly for a while :-( Gasohol apparently gives poorer mileage too, but I
like it once in a while to clean out any moisture / gunk.

Using the wrong octane is also a waste. Check the manual.

'Curly'

 

The manual says 91 Octane. Can't find any other than regular (87),
plus (89), and premium (93).

A can of Techron concentrate has been added to the tank. Will see how
it turns out.

Thanks.

 

just curious how dirt would get in the fuel system from driving on dirt
roads. i know it would clog the air filter faster