Putting high octane gas in occasionally. Wondering if the high octane gets stale


#1

…sitting in gas station tanks due to little use. I usually use regular but thought of occasionally using higher octane (when eligible for free fill-up) and wondered if the premium tends to get stale from seldom usage. Thoughts?


#2

Absolutely NOT…you’re just wasting your money.


#3

No it does not get stale and if your vehicle does not specify premium why do it?


#4

It MIGHT help keep your injectors a bit cleaner. Though not likely as good as just dumping a bottle of Techron in your tank every 6 months or so. But more likely if your car doesn’t require it, you’ll get worse mileage with it and just waste money.

I think it’s possible that high-octane gas can get stale as it might contain more volatiles and may not get used as much, especially in some more backwater stations. If you use a station that is pretty popular, it’s likely you won’t have problems with any grade of gas.


#5

In some stations-at least two that I go to 200 miles apart, the high octane, 91, is a non-oxy gas for off road stuff, boats, and lawn mowers. It won’t hurt your car at all and won’t go stale as fast like the normal stuff, but I don’t think it’ll really do much good. If its non-oxy, it’ll have a big black label by the nozzle.


#6

I see it as a waste of money and will accomplish very little if at all.


#7

It’s a complete waste of money.
The only difference between premium fuel and regular is in its readiness to detonate. Regular detonates too easily for engines with high compression pressures, making it explode in the cylinders too early, before the spark plug fires. Premium detonates a bit less readily, allowing the piston to compress the fuel without it self-igniting, allowing the spark plug to ignite the mix at the proper time.

It should be said that all gas regardless of its octane can become stale over time. There is a product called “Stabile” on the market to keep stored fuel volatile for a longer time period, and for engines that are very rarely run (cars, snowblowers, lawnmowers, etc.) it’s advisable to add some Stabile.


#8

The question is if the OP is risking stale premium gas. As long as this is a high-volume station, I wouldn’t worry about it.


#9

You can put the higher octane gas in for a free tank, but it won’t help your car at all unless high test is required or recommended. If it does help, you should use high octane at every fill up.


#10

Good point, texases. It may help the OP feel better to know that a great many new cars in all categories recommend or require premium. Manufacturers are trying to get good mileage with small volume engines by boosting cylinder pressures with turbochargers and even superchargers, making premium necessary in even economy cars. I’d bet that premium fuel tanks at the gas stations “turn over” just as rapidly as regular fuel tanks.


#11

Dont do it,if your car doesnt need it,a lot of stations vend alcohol free regular.


#12

On a trip, I accidentally put a higher octane fuel in our 2003 Toyota Runner. I was hoping the computer might advance the timing and the miles per gallon would increase. Mrs. Triedaq claims that the 4Runner likes her better than it does me, so I was hoping that the 4Runner might like the higher octane fuel, just as I like a bottle of Michelob after drinking the Hamms beer I get on sale for a case of 30 for $9.95. Well, the higher octane fuel made absolutely no difference in the mpg on the 4Runner. At 15¢ more per gallon on a 15_gallon fillup, I just threw away $2.25.


#13

Huh, beer and high test? I don’t know what beer costs but we picked up some Yuengling in Ohio to bring back for friends. It was $20 for a case of 12. I thought that was cheap.

Back to gas. Wife was 150 miles out on the way to the cabin and filled the tank at our normal station. She called me in a panic saying she accidentally used the 91 non-oxy for off road use instead of the normal premium. I said the car will be happy like getting a doggy treat. This was the same town where she had my diesel when it developed a knock and cost me an engine so she is a little gun shy.


#14

The ECU doesn’t advance the timing if you put in premium, it retards timing if it detects detonation. If you put regular in an engine that needs premium, the detonation will retard the timing and your engine makes less power and uses more fuel. If you put premium in an engine that’s designed for regular, you just threw a bunch of money away.

Detonation is not the fuel igniting before the spark plug fires, that’s pre-ignition. You can have pre-ignition without detonation. Sustained detonation can turn into pre-ignition as the cylinder head parts become hot enough to auto-ignite the fuel, leading to a viscous circle that can melt a hole in a piston.
Detonation is when the advancing flame front compresses and heats the remaining fuel/air mixture to a degree that causes auto-ignition, a shock forms and the sudden compression of the shock wave front auto ignites the fuel which reinforces and adds energy to the shock wave, making it even more severe. That shock wave advances at the speed of sound, that is the speed of sound in a highly compressed gas that’s already been heated to over 1000 degrees before the shock wave reaches it. Much faster than the speed of sound in room temperature air.


#15
Dont do it,if your car doesnt need it,a lot of stations vend alcohol free regular.

That depends on where you live…Can’t find them in NH or MA (unless at a marina). Pretty sure they aren’t allowed in NY also.


#16

If memory serves, kmccune lives in Mexico.
I don’t believe this gas is available in the U.S. except for marine and aviation use.


#17

I can’t imagine a gas station that does any kind of business that keeps gas in the tanks long enough for it to go stale. If a station goes that long that the gas is stale it surely wouldn’t even be in business anymore.

Depending on what brand you’re talking about, the premium grade may have significantly more detergent than the regular grade. The benefit of that is using it on a regular basis and over the long run, not one tank here and there. But using it is a no harm/no foul deal. The difference in price is less than a cup of coffee.


#18

I have seen “ethanol free regular” in Wichita Falls TX and Abilene TX. I think it has more to do with the vicinity of a large metropolitan area than it has to do with which state you are in.
Most of New Mexico is so unpopulated that if everyone there drove a 1950’s era car, you would hardly be able to tell the difference in air quality.


#19

Mountainbike, Irlandes lives in Mexico. Kmccune lives in rural Western Virginia.


#20

Apologies for the error. I always did have a terrible memory for detail. No offense was intended to anybody, and if anybody took any you have my sincerest apology.

B.L.E., you may be right. There actually isn’t regulation requiring 10% at the pump, only approving it for over-the-road use, which is actually up to 15% now. I believe there are, however, regulations mandating the percentage of fuel sold by the refineries that has to be biofuel (which ethanol is).