"Non-aromatic" fuel

[3930dave]

Need some help, from somebody who paid more attention in chemistry class than I did.....

This was in a Stihl promo, emailed today:

STIHL's Outdoor Buzz: MotoMixｮ Premixed Fuel

In case you can't get to that .ca page, bulk of text is:

New ethanol free, fully synthetic and highly biodegradable premixed engine fuel.
MotoMix?ｮ - Official fuel of STIHL?ｮ Timbersports Series
NEVER WORRY ABOUT MIXING AGAIN!

Right mix: Perfect 50:1 mixture of 92 high-octane fuel and the protection of STIHL HP Ultra two-cycle engine oil
Longer shelf life: 2 years once seal is broken*
Environmentally Conscious: Non-aromatic fuel; fully synthetic, highly biodegradable engine oil
Extended Warranty: Two year warranty
with purchase of 3 cans of MotoMix?ｮ
(ask a STIHL Dealer for details)


* It requires to be stored in a cool, well ventilated area to avoid vapour build up. Avoid prolonged exposure to temperatures in excess of 120˚F /48˚C.

1) It looks like Stihl has taken note of the boutique fuel business going on in the small engine market, and decided to get into the game. Good news, IMO, esp. for the people getting stuck with ethanol only fuel :thumbsup:.

2) What is "Non-aromatic fuel" ? Corp Legal has them putting the "vapour build up" warning in, so I'm looking for a better explanation from a Chemist, or A level Chem student.

:scratchchin:

Rgds, D.

 

[JasG]

Non-aromatic fuel is fuel which is supposed to be composed of straight chain hydrocarbons. This is supposed to be better on seals because it causes little swell of rubber.

Here is a low aromatic fuel.
Shell Unleaded 91 Low Aromatic FAQs - Australia

If you search online you can find more and probably better answers.

 

[3930dave]

Thanks for pointing me in the right direction Jas.

My initial vague recollection was something to do with volatility and evaporation rates. That turns out to be in the ballpark, as it seems one of the reasons for implementing this is to reduce abuse by people sniffing gas.

That Shell link notes a reduced density with their fuels, which may affect carb'd engines.

Rgds, D.

 

[Scooby074]

Basically its free from Aeromatic hydrocarbons. Things like Benzene and Toluene. A couple nasty chemicals and potential carcinogens.

Husquvarna has a similar product called "Aspen Fuel". It seems to be pretty popular in Europe. Not sold here under the husky name AFAIK.

Aspen Petrol Info - Husqvarna Chainsaw Specialists

Br舅sle f? folk som bryr sig - Aspen alkylatbensin

[url]http://en.aspen.se/About_alkylate_petrol/FAQ
[/URL]
http://www.husqvarna.com/se/aspen-det-ar-skillnad-pa-bensin-och-bensin/

 

[CliffordK]

Interesting.

Octane, of course, is C[sub]8[/sub]H[sub]18[/sub], and C[sub]8[/sub]H[sub]18[/sub] (Cyclooctane). If they are making a fully synthetic fuel, they could make it be 100% Octane (plus oil, if a premix).

$10 per quart sounds a bit steep!!! Even $5 per quart would be high.

Anyway, I don't think I'll run out and get it. It might be most appropriate for those engines that are rarely used, to help prevent rusting and varnishing. Otherwise, I would think ordinary fuel would be fine.

Ethanol?

I have heard of problems with oil dissolving in high alcohol mixes (E85), with some people using vegetable oil, or biodiesel as a fuel additive instead of the off the shelf additives.

 

[3930dave]

The push is on in some areas now for E15.... this story ain't getting better.....

Even if you know your way around a carb (fewer people do today), doing rebuilds due to #### fuel is a PITA. These boutique fuels seem to be gaining traction, esp. in areas with no Efree gas available.

Still wondering about the performance hit w/o aromatics..... got more reading to do.

(When I type a capital "Eye" on here, I see an exclamation mark. Don't see it on other sites, or if I open a text editor..... :confused3

Rgds, D.

 

[CliffordK]

I tried to find BTU's (or your favorite energy unit) per gallon of different fuel components. I think it may be very close for Benzene or Toluene and "gasoline".

I did see that Hexane has more BTU's per Pound than Benzene, but at a lot lower density.
Here is one person that did a road test with 100% Octane fuel, and found slightly better fuel efficiency with the 100% Octane.

Perhaps it is more complicated than that.

Consider Hexane:
C[sub]6[/sub]H[sub]14[/sub] + (9.5)O[sub]2[/sub] --> 6CO[sub]2[/sub] + 7H[sub]2[/sub]O

Benzene:
C[sub]6[/sub]H[sub]6[/sub] + (7.5)O[sub]2[/sub] --> 6CO[sub]2[/sub] + 3H[sub]2[/sub]O

So, by going with the non-aromatic fuels, one likely throws off the oxygen balance somewhat which could mess with the carburetors, although it may be a simple needle valve adjustment. More moles of output for an equivalent weight/volume input may in fact mean more expansion, and better power without the aromatics. Is the oxygen per stroke more or less fixed? In which case, one might be able to use more benzene per stroke than hexane.

Anyway,
For the 2 cycle engines, you add oil as a lubricant, and they apparently either run fine without the aromatics, or can be tuned to run without them.

It does seem like a waste to do all this, but cleaning rust or varnish out of the carbs can be a pain, although often it can be done without replacing all the gaskets.

Gas stations could probably sell special bulk fuels for 2-cycle and small engines, but most would likely choose not to do it due to having to have redundant handling, and dealing with lower volumes.

 

[3930dave]

It seems that non-aromatics have lower energy density.

Figure 5 in the attached pdf shows the energy difference for the diesel fuel. Don't know the #'s for gasoline yet, but I suspect the same relationship holds.

Rgds, D.

 

[stevo84]

One main point which seems to have been missed is that here in Australia, non-aromatic fuel is only available in places where petrol sniffing has been a problem.
You might even go as far to assume that's why it was developed. I have heard that you can't get high on this stuff.
Places like Alice Springs only sell this type of fuel.
I have only ever seen it in the NT and the Shell site lists where it is available.

 

[3930dave]

Because of the nature of the problem, perhaps the availability is not stressed.

Gas-sniffing is a problem in some of our Canadian remote settlements too. I don't know at the moment if anything is being done here about gas formulation.

In Canada, there has been a long term push to reduce solvents in general - ex. most retail paint is now water based. Oil based paint is available, just much less so than in the past.

Typing this now, I'm musing about what affect removing the aromatics has on low-temperature gasoline performance. Our winters have been warmer of late, but -48C would not be a good time to find out that non-aromatic fuel doesn't ignite as readily. :cold:

Rgds, D.