my VX gas tank

[1993CivicVX]

So umm.. over 11 gallons my last fillup! Sheesh.

Maybe both gas stations are in on the same conspiracy I filled up in the one across the street from the one I had suspected of miscalibration.

Anyway, at 335 miles I had 1/4 of a tank of gas.
125 miles later I fill the car up and it takes over 11 gallons. About 1/2 of the last 125 miles was driven with the A/C on to keep the window from fogging up. 75 of those miles were driven with a load of about 200-250 pounds.

Does the extra 200-250 pounds have a huge effect on my gas mileage? It definitely did on my acceleration. I was seeing 2500RPM frequently. had to go 3000+ a few times because the route was lots of big hills. This was also driving with the A/C to keep the windshield from fogging up.

Anyway, I figure 1/4 tank left meant I had used about 7.5 gallons, which means 3.5 gallons were used for the last 125 miles. That means a measly 35.4mpg for those 125 miles. If I had used 8 gallons and thus had 3 gallons left when I started the 125 mile trip, then it would have been 41.3mpg for those 125 miles driven. What does anybody think.

[Gary Palmer]

I can't say what you can or can't assume, for your car, as far as gas, gauge and consistency. I can tell you that on my 89 Honda Wagon the gas gauge is very non-linear. I can't do the 1/4 tank represents x gallons of gas, with any degree of consistency. As far as I'm concerned the Honda gauge is just a very general indicator and until I have used a tank and refilled I can't guess a consistent number for how much gas it will hold.

I try to just use it as a very general approximater for whether I need to be looking for a gas station or not. Otherwise the inconsistency is frustrating because I'll get sucked into thinking I'm doing better, then all of a sudden it looks like I'm doing worse and then when I'm at the gas station, it still takes a little over 9 gallons, unless I go below E, which I'm just not comfortable with doing.

[1993CivicVX]

I think I'd have better time guessing how much gas is left in my tank by how I've been driving than looking at that unreliable, lying, inconsistent needle. Did Honda go out of its way to make the gauge as unreliable and inconsistent as possible? Seems they did!

[VetteOwner]

no all gas guages are liek that. thier not ment to be super accurate

[1993CivicVX]

Originally Posted by skewbe

Not all tanks are created equal, they put whatever bumps they need to in them to get them to fit with the required amount of gas.

I hijacked DiamondLarry's Prius record thread so I moved my reply to here skewbe and SVOboy!

I see. Thank skewbe. But then, based on this, how much gas left at 1/4 should be consistent even if it's not really 1/4 of gas. Whataver amount of gas is in the tank when the needle reaches 1/4 should be consistent, no? Yet, I barely went 125 miles from 1/4 to being so empty my car took over 1 gallon more than the size of my tank!

[skewbe]

It's just an example, the tank could be on an angle, have different bumps, whatever. Also note that the float motion is part of a circle, not linear (straight up and down) so it will rotate faster towards the bottom. And the gauge and sender might have issues of their own. It hasn't been a real exacting bit of instrumentation in cars for whatever reason.

[slurp812]

Originally Posted by skewbe

It's just an example, the tank could be on an angle, have different bumps, whatever. Also note that the float motion is part of a circle, not linear (straight up and down) so it will rotate faster towards the bottom. And the gauge and sender might have issues of their own. It hasn't been a real exacting bit of instrumentation in cars for whatever reason.

There are non linearities with the arm movement also. And that arm is connected to an variable resistor (like an analog volume control on a radio) and that can have its own non linearities. Mine goes something like this:

0 miles at full
~150 around 1/4
~275 at 1/2
~400 at 3/4
~500 near E
and I can go below E quite a bit, like most cars and get like 540-600 when the light comes on...

The only thing I can say for sure, is that its NEAR F when I fill up, and somewhere below E when the light comes on! It varies from tank to tank...

[1993CivicVX]

Well, this tank, for whatever reason, really filled to the top. Hence the 11 gallons and the still at F at 130 miles. So my FE for this tank should be in the low 60s again.

[1993CivicVX]

Gas tank at F line at 130 miles.

Gas tank finally drops below F somewhere between 130 and 155 miles (wasn't driving these miles, so I don't know at what point it dropped. I did tell Tobias to drive easy tho!)

Gas tank just about to say good bye to the 3/4 mark (as in dip below) at 244.6 miles. Going for 600 miles.

Gas tank first touches and dips below 1/2 way mark: ~275 miles.

Gas tank a smidge below 1/2. 306.4 miles.

oil change with synthetic Mobil 1 rated to be changed at 1 year or 15,000 mile interval. ($7.48/qt)

Gas tank at about 1/4 at 362.4 miles.

Gas tank at about 1/8 at 419 miles.

Gas tank just above line at ~475 miles.

Gas tank gauge is cozying up to the E line at 510 miles.

Beginning to nudge below E line at 523 miles.

Below E line at 533 miles.

Filled up at 573.5 miles. Filled up 10.6 gallons. I have no reason to believe my tank isn't 10.0 gallons, so why all of a sudden I'm putting in 10+ gallons when before I was putting in 8 gallons at the same gas gauge readings. Totally flummoxed. 54.1mpg. Blech.

[1993CivicVX]

Oh, what the suck. I guess I have to blame it on the weather but man, it's discouraging. Was really expecting 60s this tank. 54.1mpg. Drove for FE the entire tank without any nonsense or anything that would have had significant impact. Dunno what to say. Disappointing at best. Considering I got 62.6mpg over a 1026 mile period with far less FE measures in place, how can I now be getting only 54mpg? Only thing to blame it on is the weather, but it hasn't been that cold, sheesh! In fact it's been unseasonably warm. So I'm stumped.