Question on Octane?

[CharBaby]

My FIL was telling me that this one(1) small engine mechanic told him...

This guy(I've never met) told my FIL the leaving gas stored in a container or in a small engine over time(a season or longer) depleats the octane. So, when storing gasoline for long periods of time, you should buy higher octane(91-93) so by the time your ready to use the gas again in, oh, lets say the Spring, the gas will have dropped the octane rating down to about 89-87, per/say.

Now, as most member here at Bob's knows; that untreated(w/o fuel stabilizer) stored gasoline does go bad over a lone period of time but, what is it that goes bad?


In our household, we only store gasoline in the gastank(s) of the the small engines or stored car(summer car) for about 5-6 months. Each spring through fall, I store gas in the tank of the snowblower with a full tank. And the the very late fall to early spring, I do the same with the lawn mower. I don't seem to have any problems with any of them. I do use Sta-Bil in the fuel.

This small engine mechanic that my FIL is speaking of is the first guy that I have ever heard mention it this way(speaking of depleated OCTANE).

Can anyone elaborate on this?

 

[ARCOgraphite]

Most small engnes dont require high octane. But, Yes, some upper volatiles will dissapear over storage time and AKI will retreat some. Doesnt matter on a 7/1 comp flathead briggs motor.

 

[Quattro Pete]

Regardless what octane it is, gasoline will go bad over time, unless is treated with something like stabil.

I'm not sure that using a higher octane will counteract the natural process of gas going bad over time, but I'd be interested to hear what others have to say on this subject.

 

[bepperb]

I've also been told it loses octane over time. For outboard motors this can be an issue, but for a Briggs I agree it won't really matter.

 

[Boss302fan]

I guess using a mid grade gas would not be a bad idea if you are going to store gas for 6 months. An extra 10 cent a gallon is not going to effect most of us...

 

[CharBaby]

And too, in my car that I store in the winter time, this car may get it's last fill up prior to winter storage, in late October(w/ Sta-Bil) and not started agian til late May/early June the following year. And I may not use up that gas in the tank till mid/late July. So, this gas in my stored summer car often will have the same gas in it for 8+ months. Been doing this for some 30+ years in this particular car. And over 40+ year in small equipment(lawnmower/snowblower and other yard equipment). Years ago, I neve used Sta-Bil or any other brand of stabilizer. I've only been using stabilizer(s) in the last 12-13 yrs or so!

I have actually had more hard starting issues when I left the gas tanks/carbs dry in the small equipment. Since I have been keeping the tanks full over a season, my starting issues are gone. And too, since I've been using Sta-Bil, the engines run smoother too! Lubrication Maybe?

 

[Boss302fan]

Originally Posted By: Char Baby
And too, in my car that I store in the winter time, this car may get it's last fill up prior to winter storage, in late October(w/ Sta-Bil) and not started agian til late May/early June the following year. And I may not use up that gas in the tank till mid/late July. So, this gas in my stored summer car often will have the same gas in it for 8+ months. Been doing this for some 30+ years in this particular car. And over 40+ year in small equipment(lawnmower/snowblower and other yard equipment). Years ago, I neve used Sta-Bil or any other brand of stabilizer. I've only been using stabilizer(s) in the last 12-13 yrs or so!

I have actually had more hard starting issues when I left the gas tanks/carbs dry in the small equipment. Since I have been keeping the tanks full over a season, my starting issues are gone. And too, since I've been using Sta-Bil, the engines run smoother too! Lubrication Maybe?


Makes sense...

 

[Ken2]

Never heard about an octane loss.

The local Honda Power Equipment shop (and I know and respect these guys) says that the regular in this region contains some chemicals that often cause sticky deposits on the engine valve stems. Some engines can be cleaned up with directly applied solvents and manually stroking the valves, and others must have the heads stripped down. They never see this when premium gas is used, even though the engine instructions and their Honda tech rep do not call for hi test. This problem might be regional, but they know their customers and when the customer changes to hi test the engines don't come back with this problem.

 

[Garak]

Originally Posted By: bepperb
I've also been told it loses octane over time. For outboard motors this can be an issue, but for a Briggs I agree it won't really matter.


I don't know if it's an old wives tale, but I've heard the same thing, from a fuel distribution centre owner, of all people. He claimed that their regular upon delivery was actually about a one mark higher in octane than advertised, to give a cushion for degradation, either in the customers' possession or in the station's possession. However, the station usually goes through enough regular, he stated, that it wasn't much of an issue.

Personally, I usually use premium in my OPE, since I don't go through a lot of gas in them, and keep Stabil in all the time.

 

[Clevy]

Octane is resistance to combustion. Gas getting old would GAIN OCTANE because it's harder to burn. Buying premium will not help the issue.
Use a fuel stabilizer or better yet just use the gas up. If it's got 2 stroke oil in it dilute it with more fuel and run it in your daily driver.
Octane has nothing to do with fuel destabilization. And buying higher octane doesn't make it last longer.

 

[Garak]

Like I said, it could be an old wives' tale, but that's what a distributor told me. He also said they test octane periodically, and that's what he said he observed.

Whether or not gas going old or stale would raise its octane number if tested is another issue, and I wouldn't care to speculate on that.

 

[CharBaby]

Thanks for all of the replys. They were all well stated!

CB