Mixed gas question

[YZ/250]

Ok, we all know its winter. How long do "you" guys keep your mixed gas around before it goes bad? Its been almost a month on my last mix. :whoa: Im still riding its just hit and miss.

 

[just_a_rider]

I only mix what I'm going to use in winter, if I don't run it all outa my bike before I crank it I'll shake my bike side to side to bring it back together.

 

[elcamino12sec]

I would assume after only a month it would still be alright, I would use it.

 

[Pete Payne]

I would have to say with the junk coming out of the pumps these days, 3-4 weeks max.

 

[adam728]

I would have to say with the junk coming out of the pumps these days, 3-4 weeks max.

This is about the 20th time this week that I have seen someone replying about how crappy gas is now days. Any proof, or references, or anything?


How long the premix will last depends on a lot of things. Castor oils break down in gasoline, and it recommended that you use the mix up right away (some people say only mix it right before riding, others say a few days is ok). Synthetic oils will last just fine, but then the gas is what goes bad. Stored in a steel container in a cool place gas will be fine for many many months, even up to a year. In a plastic can you might get a few weeks, max. The plastic "breathes" and allows the light hydrocarbons to evaporate out, lowering the RVP, and making varnish buildup more likely.

 

[Rich Rohrich]

This is about the 20th time this week that I have seen someone replying about how crappy gas is now days. Any proof, or references, or anything?

Below are a couple of reference papers I have on my hard drive. They are worth the cost if you are really interested in the subject. ($14/paper direct from the SAE) There are plenty more references out there on the EPA federal website, and some states publish local fuel quality data as well. Pump fuel is just a really poor for high rpm engine purposes, and old pump fuel only makes things more complicated. The basic quality of fuels may actually have improved over the last 15 years based on data from some long term studies. The problem is during that time the basic makeup of the fuel's distillation curve, and carbon/hydrogen ratios of the components used to blend pump fuel were being designed for engines with long pre-heated intake tracts running in a very narrow, and by comparison low rpm range. So even if there is less trash in the fuel, it's suitability for our purposes hasn't taken a turn for the worse. These fuels also seem to be less stable during long term storage than they were years ago. Given that we have no idea how old the fuel is before we even pump it into a gas can, it's silly to think you can "know" how long fuel will sit.

If your fuel is going to sit for extended periods of time it's advisable to keep it consistently cool(or cold) and dry along with adding stabilizer to the fuel. Stabilzers won't stop the fuel from going flat and boiling off the low ends which aid starting warmup and throttle response, but it will help keep the fuel from oxidizing to the point where it will clog jets, or turn completely.

Fresh fuel is cheaper and easier in the long run. ;)



SAE paper # 2004-28-0054
Gasoline Quality and Its Effects on Intake System Deposits


Abstract:
Gasoline can oxidize during storage giving rise to formation of gums, which cause deposit formation in the intake system of engines, affecting the performance, drivability and emissions characteristics of the vehicles. To evaluate the deposit-forming tendency of gasoline, a small-scale engine test method using a modern technology gasoline engine, was developed and reported in SAE paper 2001-28-0039. Further work has been done in this area to demonstrate the ability of the test method to distinguish between different qualities of fuels. Data on the performance of different base fuels and various commercial deposit control additives, with regard to their effect on the deposit forming propensity and cleanliness characteristics, in the engine combustion chamber and intake systems is reported. In order to investigate the effect of prolonged storage of gasoline on deposit-forming tendency tests were conducted with base fuel samples stored over a period of two years. Results of the tests show that during prolonged storage, lighter fractions of olefins evaporates and remaining gasoline oxidizes giving rise to the formation of gums and gum precursors that can increase the deposit-forming tendency.

SAE paper # 1999-01-3584
An analysis of 1996-98 gasoline quality in the United States

Abstract:
The importance of the fuel in providing improved vehicle performance and reduced emissions has become widely recognized, especially in the past ten years. In 1998 an SAE paper was presented providing a systematic analyses of 1996 United States gasoline quality. This paper extends the methodology of that paper to include the impact of fuel composition on evaporative emissions, and it provides analyses of gasoline quality for the years of 1996, 1997 and 1998.

 

[Pete Payne]

My proof is that my bike will ping after the fuel sits in the fuel jug for 3-4 weeks . Seems to happen everytime my frequency of riding slows down and the fuel does not get used up quickly.

 

[trailqueen]

How do you dispose of old gas/mix?

 

[BSWIFT]

Just my $.02.
First, I'm not about to dispute SAE papers, I'm not qualified. Rich studies this topic and covers it quite well, so well, it goes right over my head. :bang:
There is a point when the question of performance loss due to "old" gas becomes very important but for most Spodes it is more of a novelty than a necessity. If I or anyone else is capable of utilizing all of the power in our offroad bikes fuel consistancy is very important. When jetting, consistant fuel quality is important to narrowing down the parameters of the fuel/air ratio to get crisp throttle response. Once the bike is jetted (this is not a one size fits all statement), we will notice fuel inconsistancies with our SOTP dyno and our ear. In the extreme temperature ranges and elevation changes perfomance will be quite noticably different and most likely detrimental to the engine.
I've jetted my 05 YZ with pump fuel, 92 octane. My SOTP dyno cannot detect month old gas from 6 month old gas. I have 4 major gasoline refineries within a 30 minute drive and from my work in these facilities, the fuel doesn't stay there long before it is trucked off to the pump. The stores that I purchase fuel from average 2 tankers per day of reg unleaded and the "premium" is topped off every 3-4 days. So how old is the fuel before I get it? No idea.
Quite honestly, I wish that my riding performance and enjoyment was so dependent on the consistancy of the fuel that I use but the reality of the matter is that the top pro's (riders and mechanics) need the fresh consistancy of their fuel to maximize their performance. As a Spode, a weekend warrior, I'm happy to have fuel to burn regardless of how old it is. If I could possibly use all of the power that my YZ makes and I needed an edge to be competitive I would be more in the know about the freshness and consistancy of the fuel I used.
Don't get me wrong, I like this topic and the information gained is all good. I don't think it will help me out considering my skill level and furthermore don't think it will effect the "grin factor" of pulling a 5th gear wheelie from 1/2 -3/4 throttle with just a twist of the wrist. I really just wish that I could ride often enough to burn all of the fuel that I purchase in a short period of time.:cool:

 

[elcamino12sec]

Disposal for mixed gas = Put it in your lawn mower.

 

[adam728]

Below are a couple of reference papers I have on my hard drive..........

What? Real information on the internet? Baloney I tell you...


:laugh:
Thanks for linking to something credible and useful. I just get kind of irked when forums start having "facts" passed around with no one really knowing anything, just a "I heard it from someone who heard it from someone who learned it from someone that sounded like they knew what they were talking about."

I'll have to check out the papers, I'm pretty sure I can get SAE papers through work (I know I've been given a few for other fuel data).

 

[MX86]

i usually don't mix it unless i'm riding after 2 weeks i dump the gas into my truck or lawnmover and burn it

 

[Pete Payne]

Watch out , 2 stroke oil will reek havoc on an automobiles catalytic converter ans some O2 sensors.

 

[adam728]

Watch out , 2 stroke oil will reek havoc on an automobiles catalytic converter ans some O2 sensors.

O2 sensors, maybe, I don't know. I've read that they will foul out in a 2 stroke, but have also seen a wideband used on a drag sled before for tuning.

Cat, nope, won't hurt it. Many 2 stroke engines (string trimmers, chainsaws, tillers) use 3 way catalytic converters, just like automotive applications, using palladium and rhodium.

 

[BSWIFT]

My own post got me to thinking :think:, in high rpm multicylinder bike engines (e.g. motogp) I would see the utmost need for a consistant stable fuel. These engines are held wide open for longer periods and then back and fourth in the rpm range. Would/are supermoto engines subjected to basically the same conditions as a motogp engine?

 

[FruDaddy]

Given that we have no idea how old the fuel is before we even pump it into a gas can, it's silly to think you can "know" how long fuel will sit.

That is a good point, and to reduce the risk of getting old/bad fuel at the pump, go to name brand stations, and more importantly buy your gas from a station that sells a large volume of fuel, they get more frequent deliveries so the fuel will be fresher. Also, if you see the tanker on the lot, you might consider going elsewhere, the process of delivering the fuel stirs up any sediment that may be at the bottom of the tank. There are filters at the pickups, but this doesn't guarantee that crap won't get by.