Gas Tank Always Full

[darkness975]

Evening (or Morning) CivicX peeps,

So, I am a bit OCD and I never let my gas tank fall below half empty. Usually I fill it up sooner, actually.

Part of it is due to concern for freezing gas lines in the Winter and part of it is the whole "be prepared if you have to take off ASAP and don't have time to gas up" scenario. Granted the former is more likely to be an occurrence than the latter but you get the point.

Anyway, I am wondering, is it detrimental in any way to not run the tank out to almost empty at least some of the time? A long time ago someone who knows pretty much nothing about cars said you don't want old gas sitting in there forever if you keep topping it off. But, does gas not mix up constantly when the car is in use?

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[jks]

No. and Yes.

 

[Civics4Ever]

I wouldn't do it. Gas does get old and varnishes I think. Good way to clog up filters.

 

[darkness975]

I wouldn't do it. Gas does get old and varnishes I think. Good way to clog up filters.

What would you say is a safe level for it to drop before filling up? I am especially concerned about freezing gas lines in Winter.

 

[bembol]

Top Tier and guessing majority add some type of antifreeze during winter season, hence the lower fuel economy.

In my 15+ years I never had a day where it didn't start. I do try to keep her at least half full.

One trick I leaned, not sure if it really works is to (for Push Start) press it twice without depressing the brake so it's ON position, let it sit for 10 seconds. I find it starts with any struggling.

 

[Mocha90210]

What would you say is a safe level for it to drop before filling up? I am especially concerned about freezing gas lines in Winter.

Are you in Antarctica? How cold is it where you live? Are frozen gas lines still a thing? I used to park outside 2 cars ago. I’d fill up around 1/4 tank, and never had any problems. Some mornings it would be -30 Celsius. And that was a long time ago, before gas had all the extra additives.

 

[dmitri]

I am especially concerned about freezing gas lines in Winter.

Freeze point of gasoline is at least -40 degrees, so I don't think that's something you need to worry about, unless you actually live in a place where temps actually drop that much (and you park outside)... Do you?

 

[darkness975]

Freeze point of gasoline is at least -40 degrees, so I don't think that's something you need to worry about, unless you actually live in a place where temps actually drop that much (and you park outside)... Do you?

No. I was just concerned about the line itself not so much the gas.

But, I suppose I'll shift my practice to filling up when it's 1/4 full instead of 1/2 full to burn through more fuel and expel the older stuff.

 

[lzaffuto]

I always fill up at 1/4 of a tank because in the past at that level if I went to work and came back home I was running on fumes. With this Civic, not so much now. But I've never had an issue leaving some gas in the tank.

 

[Civics4Ever]

I had always heard to leave it at least half full for winter. I've never had a gas line freeze.

 

[tacthecat]

We almost always run our tank down to the Lo-Fuel warning light before even thinking about filling up. For the lower 48 (and most of Canada) there is NO risk of a gasoline freeze-up. If moisture got into your sealed-to-the-atmosphere tank, or you got a load of gas with a very high water content then leaving your car out overnight in zero degree F or below, or several days where the temperature never reached freezing AND the car wasn't started or driven, the separated water "COULD FREEZE". Before "sealed gas tanks" there was a very slight risk of high humidity air getting into a partially filled tank and for carbureted engines the float bowl could eventually partially fill with water and the engine would not perform well when accelerating or cornering hard. The only risk of running a very low fuel level is running out of gas and that's not a good thing.

 

[brienp]

Although the chemical makeup of gasoline varies from location to location heres a short list of chemicals that are almost always present in gasoline regardless of location and their corresponding freezing points; but suffice to say, unless you live somewhere with consistent -70f weather the fear of gasoline freezing is unfounded. Also, gasoline isn't a pure liquid, like H20, it doesn't "freeze" in the sense you're thinking. Its constituent parts begin to coagulate together and start to form a "waxy" glob as they near their individual freezing point, but, for example, in order for Ethanol to start coalescing the temperature outside would need to be slightly lower than -170f

Heptane -90.6c -130f
Hexane -95.3c -139.54f
Octane -57c -70.6f
Toluene -94.99c -138.982f
Ethanol -114.1c -173.5f

Some colder climates add

Butane -140c -220f
Pentane -129.8c -201.6f


As for sediments, that is the purpose of the fuel filter, to catch the solidified particles before they are injected into the engine for combustion. I did hear an argument once that many auto manufacturers place their fuel pumps inside the gasoline tank and use the gasoline as a means of cooling the fuel pump, which would mean with those particular cars, running on E consistently would allow the fuel pump to over heat on a regular basis; however, I have no idea where Honda stuffed the fuel pump on the Civic so this argument may or may not apply to the civic.

 

[brienp]

oops, forgot the part about gasoline going bad. There's no hard expiration date for gasoline. The long answer: most of the refined chemicals in gasoline are stable from 6 months to 2 years depending on how you store them, the cooler the storage temp the longer they'll last. Gasoline is blended differently depending on the time of year and location in the US. The other part to the equation is, gasoline isn't like milk you buy at the store where its squirted out of cow, pasteurized, bottled and shipped near "instantly" to the store to be sold. Refined petroleum products can sit for up to a month at the refinery before being delivered to your local gas station, where, its pumped into gigantic underground storage containers to sit for god knows how long before its emptied....except...it never really goes empty because a new batch will be delivered before then, mixing the previous "old" gas with a "fresh" batch (that could also be over a month long if it sat at the refinery).

The Short Answer: fill your gas tank at least every 6 months and keep in mind that summer gasoline is more difficult to start in winter.

Something to think about: Gasoline, the liquid, isn't really all that flammable, its the fumes that come off it that are insanely combustible. One could argue that an empty tank (filled with gasoline fumes) is like driving around with a giant bomb strapped to your ass just waiting for a spark to ignite in a glorious Hindenburg fireworks display where as a full tank would have fewer gasoline fumes.

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