Gas Guage

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Mazda CX 5 Touring
I've only owned my cx-5 for a short while and have made two trips of ant length. I travel 194 miles one way to visit someone and return. Before I leave I make sure the tank is as full as I can at a very slow speed on the pump. This last trip it looked as if I might make it all the way home before having to refill. I normally start looking for gas at the quarter tank mark. I have what is a type b insrturment panel and it has segments in each quarter tank segment with a few more segments in the last quarter. Two of the segments in the last quarter had disappeared when I stopped for gas @ 25 miles from home. When I gassed up I got 13.5 gallons in the tank which with a 14.8 gallon tank I only had 1.3 gallons left and I still indicated over an eighth of a tank left. With each quarter representing 3.7 gallons an eighth of a tank should represent 1.85 gallons. This may seem like splitting hairs but I'm dubious/nervous about the accuracy of the gas gauge. I also noticed that when I topped the tank off the night before I got 4 gallons in after expending 157 miles which works out to @39 MPG. I'm pretty sure I reset the mileage after the previous fill up. The mileage from the long trip worked out to @26.5 MPG. Mileage seems to be all over the place.
 
Do you always fill it to the top, or do you also just let the pump shut off on it's own and call it good? It puts in between 13-13.5 gallons when I fill it from 0 miles to empty before the pump shuts off on it's own. After which I can put in another 3-3.5 gallons before it's to the filler cap.

The gauge is fine, they put in a buffer for people after you hit 0 miles to empty. Figure 1.5 gallons left after you hit 0 miles, I wouldn't push it too far if you can help it though.
 
you are also assuming the pump is 100% accurate...and that your gas tank is linear.
 
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I ran mine till there was only one bar left. Filled it up and at the first 'click' the meter said i pumped 11.8 gallons. I had 3 gallons left until completely empty according to Mazda specs. With my average MPG of 32, that means I could have theoretically gone about 100 miles till the tank was bone dry. The trip meter said I had about 15 miles left.

Honestly, in all of my vehicles, not one had a linear or "true" level fuel gauge. I wouldn't worry about it too much.
 
I've only owned my cx-5 for a short while and have made two trips of ant length. I travel 194 miles one way to visit someone and return. Before I leave I make sure the tank is as full as I can at a very slow speed on the pump. This last trip it looked as if I might make it all the way home before having to refill. I normally start looking for gas at the quarter tank mark. I have what is a type b insrturment panel and it has segments in each quarter tank segment with a few more segments in the last quarter. Two of the segments in the last quarter had disappeared when I stopped for gas @ 25 miles from home. When I gassed up I got 13.5 gallons in the tank which with a 14.8 gallon tank I only had 1.3 gallons left and I still indicated over an eighth of a tank left. With each quarter representing 3.7 gallons an eighth of a tank should represent 1.85 gallons. This may seem like splitting hairs but I'm dubious/nervous about the accuracy of the gas gauge. I also noticed that when I topped the tank off the night before I got 4 gallons in after expending 157 miles which works out to @39 MPG. I'm pretty sure I reset the mileage after the previous fill up. The mileage from the long trip worked out to @26.5 MPG. Mileage seems to be all over the place.

The CX-5 is the pickiest vehicle I have ever owned when it comes to "getting good mileage". Headwind? Minus 5mpg at 75mph. Slight incline? Same deal. It's just a very finicky weed-whacker powered SUV. All there is to it. Any extra strain requires a LOT of extra work pushing the engine out of its typical BSFC pretty badly for that rpm when under more load. My V8 powered vehicles got the same mileage regardless of what you did to them, unless it was a lot of WOT runs.

The gas tank thing is normal. I've never owned a vehicle that used gasoline proportionately throughout the sweep of the gauge.
 
I've found the fuel gauge on the CX-5 to be extremely linear, almost to the point of being anal. Someone spent a lot of thought on how it would report exact fuel levels. The only oddity is that it is extremely conservative. In other words, when the Trip Computer reports "0 miles remaining" there is still at least 2.2-2.4 gallons left. With the 2.0L engine and AWD this translates to almost 100 more miles if you are cruising at 60-65 mph. Other than that, the fuel meter is over-engineered compared to other vehicles I've been familiar with. Very precise for the range it deals with.
 
I've found the fuel gauge on the CX-5 to be extremely linear, almost to the point of being anal. Someone spent a lot of thought on how it would report exact fuel levels. The only oddity is that it is extremely conservative. In other words, when the Trip Computer reports "0 miles remaining" there is still at least 2.2-2.4 gallons left. With the 2.0L engine and AWD this translates to almost 100 more miles if you are cruising at 60-65 mph. Other than that, the fuel meter is over-engineered compared to other vehicles I've been familiar with. Very precise for the range it deals with.
The absolute worst was my 2001 Trans Am, which is a tie with my 370Z. I ran out of gas with 1/4 tank in the 370Z (gauged), and could actually add 1/8th tank of gas to the WS.6 by flooring it (by the gauge). Both gauges were functioning normal to spec.
 
Fuel gauge in our old 06 Mazda 3S was, over time, much more of an rough estimation once it got to about 1/3ish of a tank. We learned to just fill it by when the light when off. 1,2,5 gallons left, we never knew for sure.

My Accord is pretty consistent and the computer is spot on. The fuel warning light goes off a bit earlier than needed, about 3 gal left.

Our CX5 is always about 2-2.5 gal remaining when filled. We have stretched it about 30-50 miles past 0 on the computer though. Living dangerously. lol
 
my experience is that the fuel gauge is not linear and that it seems to deplete faster during the last quarter tank left than at the beginning. i do know that incline can affect what the gas gauge is reading so if you are in a hilly region this could mess up your numbers a bit.
 
my experience is that the fuel gauge is not linear and that it seems to deplete faster during the last quarter tank left than at the beginning. i do know that incline can affect what the gas gauge is reading so if you are in a hilly region this could mess up your numbers a bit.

I get higher HWY. MPG when I have a full tank and/or about 40 lbs. in the trunk. The aerodynamics of the car are probably set for a average load of people/cargo.

If you travel unloaded or lightly loaded it could make you think the last quarter tank is not proportional to the first quarter tank. Also, topping off your tank will make the tank bigger from 3/4-full. I never top off.
 
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I go with the Mazda recommendation of refueling at ~ 1/4 tank and almost never lit it get below 1/8. I don't believe in " topping up to the cap"
 
Thanx for the replies. Yes Ice I let the pump shut off then like most people I put it on medium speed and when that shuts off I go real slow until I can't get more in. Seems like it's another 3 to 3.5 gallons after that. I wish it had a bigger tank. Gas pumps have to be fairly accurate inlinev because the state randomly check stations and update the state stickers. I didn't buy the vehicle for the gas mileage I bought it because it's a lot more comfortable than my last vehicle. I like the car but I think it might benefit from a slightly more powerful engine. Maybe something like a 3.0 v6 and a bigger gas tank. By the way I've got the 2.4.
 
Yes Ice I let the pump shut off then like most people I put it on medium speed and when that shuts off I go real slow until I can't get more in.

Most car makers have warned against the old practice of "topping off" a tank for at least 10-20 years!

When I observe other people at filling stations I estimate only about 1 in 10 top-off. That's 10% (not "most people"). Of course there could be regional differences depending upon whether people read their Owner's Manuals or not. I know some areas of the Country have shockingly high rates of adult illiteracy so that probably contributes to this unwise habit. The CX-5 Owner's Manual specifically instructs to stop fueling when the pump shuts off and to not top-off.
 
Thanx for the replies. Yes Ice I let the pump shut off then like most people I put it on medium speed and when that shuts off I go real slow until I can't get more in. Seems like it's another 3 to 3.5 gallons after that. I wish it had a bigger tank. Gas pumps have to be fairly accurate inlinev because the state randomly check stations and update the state stickers. I didn't buy the vehicle for the gas mileage I bought it because it's a lot more comfortable than my last vehicle. I like the car but I think it might benefit from a slightly more powerful engine. Maybe something like a 3.0 v6 and a bigger gas tank. By the way I've got the 2.4.

It would certainly benefit in the real world, I think, but on paper and EPA tests, the mileage would suffer. I'm averaging about 23.5mpg 70% highway, 30% city, tank after tank after tank. Have for the last 15k miles. In comparison, I flogged the everloving s*** out of my 370Z, and averaged around 19mpg in it around town/never exceeding 55mph except on blasts onto the freeway for the 1/4 mile I was on it. My Grand Jeep Cherokee was the same, except a bit less aggression, and I averaged around 14.5mpg really sticking my foot in it pretty hard and often. This CX-5? I can't even meet city EPA on a 70/30 cycle. Mainly because the highway here is a 70mph highway, which I drive at 75, and it is hilly. Still...I find it lame in the real world. In the paper world, it scores nice and pretty, though. A larger motor would hurt that pretty little paper-stat.
 
Most car makers have warned against the old practice of "topping off" a tank for at least 10-20 years!

When I observe other people at filling stations I estimate only about 1 in 10 top-off. That's 10% (not "most people"). Of course there could be regional differences depending upon whether people read their Owner's Manuals or not. I know some areas of the Country have shockingly high rates of adult illiteracy so that probably contributes to this unwise habit. The CX-5 Owner's Manual specifically instructs to stop fueling when the pump shuts off and to not top-off.

I've topped cars off, and not. Never EVER have I seen or heard of anything bad resulting, even when I worked at a dealership. I'm sure in theory it's bad. Mainly, I think it's probably about some EPA tree-hugger crap. I've seen and done it too many times to think it harms the EVAP system physically, except in theory.
 
Thanx for the replies. Yes Ice I let the pump shut off then like most people I put it on medium speed and when that shuts off I go real slow until I can't get more in. Seems like it's another 3 to 3.5 gallons after that. I wish it had a bigger tank. Gas pumps have to be fairly accurate inlinev because the state randomly check stations and update the state stickers. I didn't buy the vehicle for the gas mileage I bought it because it's a lot more comfortable than my last vehicle. I like the car but I think it might benefit from a slightly more powerful engine. Maybe something like a 3.0 v6 and a bigger gas tank. By the way I've got the 2.4.

3-3.5 gallons post shut off?!? Maybe .3 but surely not 3+ gallons. Something doesn't jive.
 
3-3.5 gallons post shut off?!? Maybe .3 but surely not 3+ gallons. Something doesn't jive.

Some pumps are more sensitive/etc. I have had the pump not allow me to fill the car at all unless I was holding it manually and not fueling very fast. I'd try another station or two.
 
I've topped cars off, and not. Never EVER have I seen or heard of anything bad resulting, even when I worked at a dealership.

The filler neck is not designed to be filled with fuel, that's why manufacturers tell you not to top-off. People here had a hissy fit about the latest fuel filler tube recall, imagine how much worse it would be if you exited the gas station and got rear ended by a drunk going 60 mph. It takes a number of miles to burn off the fuel that is outside the fuel tank and the fuel shut-off flapper valve inside the tank can't operate as designed when it's submerged. I fail to see a similarly compelling argument why topping off is necessary.

Unless of course you want to increase your chances of gaining admittance to this exclusive club:

https://mpora.com/multi-sport/there...but-these-have-got-to-be-some-of-the-silliest
 
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