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points by LordDragonfang 1 day ago | 0 comments

> unless you have stockpiled gas

And are regularly rotating that stockpile, because gasoline has a shelf life measured in months

edit: Apparently this leans more technically-true factoid than fact, thank you replies

Unless you are trying to race your car at the drag strip with charged air and hit your best times, that isn't true at all and I don't know why people keep saying it. You think everybody empties their lawn mowers, snow blowers, snowmobiles, generators, etc. every year of gas or before trying to start it up again the next year? No way.

Simpler gas equipment like mowers and generators don't have enough compression to really care about anything but ancient gas, and if you run any vehicle that is multi-fuel capable it can detect and adjust compression based on a fuel's capabilities.

Ive been repairing and fixing junkers of cars, mowers, ATVs, generators, and more for 30 years and not once has bad gas stopped something from running. I only remove it if it was clearly having water raining into the tank. In every other case where I couldn't start something after sitting around for 5+ years, it was from the gas gumming up in the carb or the shitty diaphragm pump, which generally means there is little to no gas left to start with.

I wouldn't even suspect gas of ever being bad unless it was atleast a few years old. If the tank was open it could have evaporated, if the tank was closed it probably ain't great gas but I bet it would still run in anything but a high compression application.

[–] dotancohen 1 day ago

> detect and adjust compression based on a fuel's capabilities.

Spark, not compression.

[–] JshWright 16 hours ago

The spark timing determines how much compression is in the cylinder at the moment the fuel/air mixture is ignited. So, while it's technically true that it's the spark timing that's being adjusted, the thing that is being controlled for is the compression.

[–] dotancohen 3 hours ago

This explanation is an excuse, and does not pass muster. I remember adjusting spark timing with a timing light flashing on the harmonic balancer and turning the distributor by hand. Cars two decades before that, which I never personally serviced but have seen, had spark adjustment controls on the steering wheel.

The term was always called spark adjustment, never compression. Compression is the thing you worry about when milling the heads or exchanging oscillating components (rods, pistons) due to changing the physical geometry of the combustion chamber.

So yes, adjusting the spark timing does technically adjust how compressed the air/fuel mixture is at the moment of ignition. But the term used to describe it has always been "adjusting spark" or "adjusting spark timing" or "adjusting timing". Nobody ever refers to that as "adjusting compression" because the term compression is used to refer to something else.

[–] Ariarule 1 day ago

You're not wrong but this is commonly exaggerated: half a year with a stabilizer is entirely doable under reasonable conditions.

[–] ljf 1 day ago

Amuses me hear this - I ran a moped from a large tank of multi-year old petrol, and it got by fine. But maybe a modern car might be more picky?

[–] ssl-3 1 day ago

Last year, I let a fairly new portable generator with low hours on sit with gas in it for 6 months and it would not fire up. It wouldn't even sputter.

That was surprising to me because it was working quite well when parked, and I'm used to doing things like leaving lawnmowers outside continuously (including over the winter) without much trouble, but that's what happened anyway.

I drained the old fuel out and replaced with fresh, and it fired up on the first subsequent half-assed pull of the starter rope.

(Which reminds me: It's been six months again already. Time to see if it still works.)

[–] timr 1 day ago

Fuel stabilizer is cheap insurance for anything that overwinters with fuel in it -- motorcycles, boat engines, etc.

You have to put in in the tank and run it for a bit to make sure that the carbs don't have untreated fuel inside.

[–] mgerdts 1 day ago

A fairly new snowblower of mine had gas left in it over the summer. Before the first snowfall of the following winter it would not start. A dissection of the carburetor revealed numerous places where small passages were completely filled with a sticky gummy substance that had to be mechanically removed. After cleaning and reassembly, it fired right up with fresh gas. Maybe the old gas would have worked just fine once it could flow. Clearly having the gas sit in there had adverse effects.

[–] ssl-3 1 day ago

The carb on this generator has a drain for the bowl. It should've been dry in there when parked. I don't know what the insides looked like because replacing the gas was easy and it worked, so I stopped troubleshooting at that point. :)

[–] greenavocado 1 day ago

I just did this as well. Fired up my moped on 2 year old stabilized gas. Runs fine.

[–] bloomingeek 14 hours ago

Be sure and use a clear liquid stabilizer! The one I used had red dye in it and it gummed up the carburetor. Also, I never use any ethanol fuel in my generator.

[–] ryanbrunner 1 day ago

We use the (inboard) engine so rarely on my sailboat I'm sure we've gone 2 years on a tank without issue before.

[–] lostlogin 1 day ago

HN is full of maintenance purists, and I do know I should do better, but... A Corolla will work fine after sitting for a year or so and it’s once-or-twice-per-decade oil change seems to work ok.

[–] bloomingeek 14 hours ago

Keep in mind that different gas "engines" have different type fuel systems. Your Corolla has a high pressure fuel pump, which forces the fuel to pressurize the injectors. The fuel is ignited by a high voltage spark system. Small engines are a "pick up" type system, which can't tolerate almost any resistance. I run my portable generator for a half hour every other month. Except for using some red dye stabilizer (which gummed up the carb), I've never had a failed start. I no longer use any stabilizer in my fuel.

[–] ssl-3 12 hours ago

Any Corolla made in the past ~35 years also has electronic fuel injection, with at least one O2 sensor as part of a feedback loop that seeks to keep the air/fuel ratio in-check. Intake air is metered and data about it is folded in for heedback.

Somewhat simplified: As long as the feedback loop demands an injector duty cycle that is within predetermined limits, it can compensate for and run reasonably well on gas that burns relatively poorly (for whatever reason it does) by simply sending more fuel into the holes.

Conditions that produce pinging are further sought to be thwarted by using a knock sensor for additional feedback.

A Corolla has a lot of stuff going for it that can help deal with fuel variations and issues in ways that a majority of small engines are completely incapable of.

It tends to resolve to: Climb in, turn key, engine starts easily, and car drives fine -- just like it has done thousands of times before.