Car's fuel economy fluctuates.
 

I normally run the car until there's 1.5 to 2.5 gallons of fuel left. I.e. I refuel after 6 or 7 days of driving to work, and my local gym. Highway and city miles are consistent each week, since I've been keeping track of the fuel cost and usage with Microsoft Excel.

To keep track of how much fuel left in the car, I use the 4 digit meter below the odometer (accumulative mileage reader). I also keep track of when the "low fuel warning" light comes on.

Week 1, the "low fuel warning" (LFW) light comes on at as low between 256-265 miles since my last fuel changed. Then on week 2, it's between 278-286 miles that the low fuel warning light comes on. Then on week 3, it's back to 256-265, then week 4, 278-286, again.

I've read that when the LFW light comes on (before usually turning off, and coming back on) there's at least 3 gallons left (meaning at least 75 highway miles for me). This means my fuel varies between 335 to 375 miles each week or refuel. This is after going to the same exact gas station, or then trying another gas station. This forces me to change fuel every 6 days, and then 7 days the next week, and then after 6 for the following week, and so forth.

Also once there's less than quarter tank of fuel left, and the car has been off for 4+ hours, it will struggle a little bit to start.

I replaced the fuel filter at 179 thousand miles, which was 5 thousand miles ago.

I've never had a tune up since, getting the car at 140 thousand miles.

What other components should I consider replacing on the car? I was thinking about the fuel pump, but that would seem to be overkill, and not actually solve anything.

Re: Car's fuel economy fluctuates.
 

miles per tank is rather useless, especially since it doesn't tell us anything about how much fuel was left in the tank.

Why aren't you keeping track in MPG? That is something we can discuss.

Ignore when the light comes on, that's meaningless. You can make a half empty tank read as empty with some aggressive driving. Actual distance traveled over fuel added to tank to get it back to full is all that matters.

Re: Car's fuel economy fluctuates.
 

I've read the Gen 3 Integra fuel tank size is 50 liters or 13.21 gallons.

I record the amount of gallons of fuel I inserted into the car, and the distance since I last time I put fuel at the petrol/gas station (always a full tank). E.g. 11.5 gallons inserted after driving 300 miles.

I need to know if a certain part of my car is malfunctioning, so I can get it fixed before bigger problems emerge.

Re: Car's fuel economy fluctuates.
 

And you haven't explained why you think something might be malfunctioning. What is your actual mileage, and how much does it fluctuate for the same driving patterns. The latter part of that is more important.

My GSR averaged 18 MPG, running just fine, due to a 45 minute 6 mile commute (burning fuel sitting at stop lights is such a waste). Later on, it averaged 31MPG (not too shabby for a car rated at 23/27) burning oil (1 qt every 300 miles) with low compression in the #3 cylinder, with a 32 mile mostly freeway commute.

So, what is your actual gas mileage, and why do you think there's something wrong with the car?

Re: Car's fuel economy fluctuates.
 

Thanks for the responses.

It seems the main culprit for fuel economy getting worser, could be lack of tire pressure especially in wheel, or possible need of tire balancing, after doing the rotation myself. I sent the front wheels straight to the back, and cris-crossed the rear wheels to the front.

I have included an excel image with previous miles driven, divided gallons inserted into the vehicle:

Aug 29th: Installed Mahle fuel filter, after owning the car for over 5 years and driving 35 thousand miles. No noticeable change in fuel economy.

Sep 6th: Pefromed a DIY oil chang, putting synthetic fuel (1st time without conventional oil, since I owned it) with k&n long lasting oil filter. No noticeable change in fuel economy.

Oct 10th: DIY tire rotation. No balancing performed. The car felt rough driving on the highway the first week. But now after 2 months, it's not really noticeable. Cold weather will make air move closer together (higher density) making the tires more "deflated".

Re: Car's fuel economy fluctuates.
 

i blame the winter blend for gasoline. i know my cars have dropped a few mpg since they switched over.

Re: Car's fuel economy fluctuates.
 

Those are all well within the normal variance for a car rated at 24/28 (I'm assuming a non-vtec Integra, the GSR was rated 23/27).

Re: Car's fuel economy fluctuates.
 

A lot of things could effect mpg. Poor maintenance, tire pressure (someone pointed that out), driving habits, stop and go traffic, hills (biggest challenge for those trying to hypermile).

Re: Car's fuel economy fluctuates.
 

I spent 15-20 minutes in the cold, pumping air to the car's tyres, and they were well below 35/33 psi. The rears were in the 20s range. I added enough for all to be 35+, with more on the front than the back. Sorry for the inconvenience.

Hopefully the fuel economy gets noticeably better. Thanks for the responses.

Edit:
After replacing spark plugs that were at least 50,000 miles old, I've noticed an increase fuel economy based on the fuel gauge meter.