Buying MOGAS from petrol stations

[kevkdg]

Hi,

What experience do people have when buying MOGAS from petrol stations for their aircraft given the rules governing the maximum you can buy in any one go as outlined here:

What is a jerry can? A guide on how to legally store petrol - BBC Newsbeat (http://www.bbc.co.uk/newsbeat/article/17548007/what-is-a-jerry-can-a-guide-on-how-to-legally-store-petrol)

For a lot of sorties you'd probably want to fill 3 x 20 litre jerry can at least.

For those running on MOGAS what's been your experiences at petrol stations?

Cheers

[Jan Olieslagers]

I never do anything else. Fuel tanks in the plane are 2 x 29 litres, I usually fill up 2 jerrycans of 20 litres each. On a rare occasion I top up from the fuel station near the airfield. Never a problem. Neither do I hear of problems from my fellow Rotax users, who all do likewise.

[Sam Rutherford]

Don't forget, very unlikely that your local petrol station sells MOGAS (ethanol-free petrol). They sell petrol - this is, or isn't important for aircraft using MOGAS on the basis of an STC (that specifically prohibits an ethanol content).

[460]

My gliding club's tug - Rotax Falke - has been running on petrol station unleaded for 11 years now; snagless.

The county petroleum officer has checked and is happy with our arrangements for collecting it: 10 jerry cans in a trailer.

[Crash one]

I regularly fill four 20litre cans at the local filling station, no problems.
When there was a fuel shortage a few years ago I was asked what the four cans were for. "To fill the aircraft". "No problem mate, that's important".
Nice to have an aviation friendly garage.
As for whether it's legal or not, I just don't tell no one!

[ChickenHouse]

I don't know any gas station selling Mogas, they sell autofuel. There are some fuels coming closer to Mogas than others, like BP and Total deliver Ethanol-free fuels, but they usually do not open that officially for aviation use.

Most current autofuel (EN) contain ethanol and some additives may be quite bad for the older aviation engines, so one has to do some research, which can be used and which not. More modern aviation engines may be less picky with Ethanol, but the POH will tell you. As most of us will run on STC, the best is to check with your STC issuer which fuels are covered, as the usual Autofuel STC is based on fuel norms no longer existent at tap (or secretly changed by EU buttheads).

I have never come across a limitation of the garage how much fuel to take in jerry cans from tap. As we are a region with quite some farming, they are used to jerry can usage. There are some limitations from carrying dangerous goods laws, you have to keep in mind though, such as: jerry cans are to be carried well vented and outside the passenger cabin, only in cases with certain stickers on it, cans no older then I guess it was 6 years, if carried more than 3x20l with certain dangerous good carriage permit etceteras - in reality nobody really cares, but if you have a road check by law enforcement, be prepared to not speak too loud ;-).

[9 lives]

I have jerry canned Mogas, but for me it is an "urgency" only means. It is simply messy and unsafe compared to proper pumped fueling. If there is no other method to get the fuel, then you have to do it, but to plan it as an operational norm is unwise. I had to jerry can Avgas into one of my planes a few wees ago, simply because the tanks were empty from an inspection, so fuel had to be brought in, as I do not keep Avgas at home. I fly my Avgas powered aircraft for fuel. I do keep a tank of Mogas for my 150.

For my experience, transporting small amounts of Mogas (a fill up at a time) is just not worth it, if it is practically possible to fly the 'plane to fuel it. As the saying goes, "if you think safety is expensive, try an accident.". If the reason for jerry canning Mogas is cost saving, it's not worth it in the big picture. There are huge risks of fire associated with jerry canning fuel - I'm also a fire fighter, I've been to the accidents. People, who were just taking 20 liters for their lawn mower, who ended up spending months in a burn unit recovering.

A part of the cost of fuel sold at the airport, is that it is the right product for the aircraft, and it is handled and dispensed safely. The less they sell, the more the costs go up. The new owner of my local airport has spent more than a million dollars in the last year, repaving the runway and apron, installing new fuel tanks and docks for the seaplanes. SO I do my very best to buy as much fuel there as I can, just to assure that he sees interest and a return on his investment. After all, it is very convenient for me to be able to fly 20 miles, and buy Avgas, rather than installing a second tank for it at home, and keeping it full.

When I have Mogas delivered (1200 liters at a time) I always specify that it must be ethanol free, and I check it before I allow the supplier to fill my tank. So far so good. That said, He has told me that my tank, which is single walled, and in a concrete dyke, will not meet the new requirements for a double walled tank, which will come into affect in a year or so, and he'll not be allowed to fill it for me any more. Then, either I invest in a brand new double walled tank, or just buy Avgas for the 150 also at the nearby airport - we'll see...

[FantomZorbin]

Ken Wallis favoured Tesco's petrol above all others!!

[ChickenHouse]

@Step Turn: I guess the Avgas story is a different one. Do you have any issue with the airport owner when using your own tank of Mogas? I know of one certain oil company, not selling Mogas at all, being very rude when autofuel is tapped at the airfield.

[ShyTorque]

Step, here in UK we have a very large number of small aircraft running on MOGAS from small private landing fields and have done so for many years, under the guidance of rules and regulations of the CAA and guidance of the LAA. Not many are fortunate enough to have the advantage of their own bulk installation though, so jerrycans are not unusual. :ok:

[Chuck Glider]

A UK centric reply but there are several issues. Buying the stuff, transportation and storage, all separate.

Buying: Individual filling stations can choose to allow, or not, purchase of large volumes of fuel in a single transaction, which is really nothing more than straightforward consumer law. Local authorities and oil suppliers may also impose maximum permissible volumes for single purchases.

Transportation: There is a distinction made in the regulations between transportation of fuel by private individuals for their own use and that done commercially. See here:
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/450057/guidance-note-23-2015-rev2.pdf from which;
Private carriage
Nonwork related carriage by private individuals of fuels packaged for retail sale and intended for their personal or domestic use or for their leisure or sporting activities is exempt from the requirements of CDG 2009; however, measures should be taken to prevent leakage of the fuel (ADR 1.1.3.1 (a)).
The previous version of that Guidance note also stated: When these goods are flammable liquids carried in refillable receptacles filled by, or for, a private individual, the total quantity shall not exceed 60 litres per receptacle and 240 litres per transport unit.

Private Storage: The regulations put upper limits of 2 x 5 litres plastic containers which have to be of an approved design, and 2 x 10 litres metal containers, which should be marked with the words “PETROLEUM SPIRIT HIGHLY FLAMMABLE”.

In Scotland, which affects me, there is also a SEPA requirement that fuel receptacles be stored in a bund or drip tray capable of containing 25% of the total receptacle volume. There may be a similar requirement in other parts of the UK.

In practice, maybe follow Crash one. (It's my business, unless I make it your business.)

[Crash one]

This all depends on your personal operation.
I fly an annex 2 Permit aircraft off a farm strip, with no fuel facilities at all on site. A local bimble south requiring a fuel stop diversion 20 miles north or east first with £15 landing fee is hardly economic.
It's a risk I know, in an estate car (US station waggon) cans upright in a fitted box.
I've had the occasional leaky can that I can smell en route, but fixed as soon as possible, and I don't throw cigarette butts over my shoulder!
Never had a problem with the Continental c90 running it for ten years. So far so good!!

Chuck glider beat me to it.

[Chuck Glider]

Yeah, a leaky can with mogas is horrible, stinky stuff. To be avoided.

[Jan Olieslagers]

Is a leaky can with AvGas to be preferred? :) I think _all_ leaky cans are to be avoided - those filled with precious delicious liquids (Glenfiddich, Chateau Mouton Rotschild, ...) perhaps even more.

More to the point: here in BE, most fields have an AvGas pump but MoGas pumps are rare. Microlighters have always brought their own. I know of one field where someone from the club will drive an open pick-up to the nearby filling station with 5 or 10 50-litre containers... On busy flying days, a second run is made around noon.

[9 lives]

The use of compliant Mogas in my O-200 has been a 100% excellent experience, for 3100 hours over 30 years, never a problem. But, I do assure that it is the right gas as per the approval - primarily, no Ethanol. Fortunately, in Canada the gasoline standards are uniform, and aside from vapour pressure variations seasonally, there's not much else to vary. Low octane Mogas has ethanol, so I do not buy it, high octane Mogas has none, so that's what I buy, and I check it. I've been told that things are not so straight forward in the US.

Ethanol fuel will run fine in aircraft engines, if you do it correctly. For several years, I was one of six pilots who flew an experimental (in the true sense of the term) C 150 on 100% ethanol. But, it was a modified aircraft and fuel system.

I got tired of the safety risk, effort and smell of transporting Mogas in jerry cans, so I bought the land, built my runway, and installed a 1300 liter gasoline tank 25 years ago. I have no issues with the airport operator. That said, I certainly know that other airport discourage dispensing for fuel on their property, which they do not control. In fairness to them, they may be required to have an emergency and fire safety plan, which would have great difficulty accounting for private gasoline dispensing. I do know of a few airports which whom arrangements have been made for private gasoline supplies - good on them!

[Chuck Glider]

Is a leaky can with AvGas to be preferred?
In terms of smell, yes. In terms of risk of immolation, probably not.
[edit]When I wrote 'leaky' I meant an imperfect neck seal more than a hole down below.

[onetrack]

Be aware that many petrol stations fuel tanks are contaminated with water and rust and are notorious for supplying contaminated fuel - and steel jerrycans are notorious for producing flakes of rust and paint as well.
As a result, make 100% sure, your fuel supplied from jerrycans into your aircraft is completely and thoroughly filtered through a funnel fitted with a mesh screen and a chamois.

[9 lives]

A story about gasoline fumes ….

About 25 years ago, the local police force was a participant in our regional “Marine Safety Day”. A grand event which drew several thousand people from all around. One of the attractions was the demonstration of a “bilge fume explosion”. To accomplish this, the demolitions division of the police obtained a derelict 28 foot wood construction enclosed cabin power boat. It was towed and moored in the otherwise closed harbour. They closed off the boat, and left a 5 liter jerry can of gasoline to evaporate all morning. A small detonator of some type was controlled by wire to shore.

My job was to operate our fireboat. I rafted up to the two police boats a safe distance back, with my crew, all geared up and ready! The police Sargent said to me: “When it blows up, don’t rush right in and put out the fire, let it get going for effect, so the crowd can see”. Fair enough, I replied, I’ll wait right here, and you tell me when to go in and extinguish the fire…”.

3, 2, 1…. Blammo! An immense fireball emanated from the boat, and the shock wave hit us (and the crowd, I presume) with a thump. I looked at the boat, as the smoke cleared, to judge the fire we were about to be asked to extinguish, and there was nothing there. The entire 28 foot boat was gone above the waterline, planks and splinters blown hundreds of feet away. I turned to the Sargent, as we both viewed the smouldering, and now sinking remaining hull, and asked: “shall we go now and put out the fire? Or, shall we let it burn for a while first?”. His return look indicated to me that they had not planned to blow the boat to bits, but rather just start a fire.

We spent all afternoon gathering up all the floating debris, all those planks with nails sticking out like angry porcupines being carry to shore across the tubes of our two Zodiac boats!

The explosive power of the vapour from a few liters of gasoline is not to be underestimated!

[dieseldo]

We ran a Contenental 0-200 on Mogas for years without any issues, then we developed a loss of power during climb out. The carburrettor had been replaced prior to the loss of power and eveything else checked out. I went flying with the pilot to see for myself. I wish I hadn't, it was very uncomfortable feeling as the engine sagged at 3-400 feet. I was very pleased when we got back on the ground. As we were short on ideas it was suggested that we dumped the fuel
(the aircraft was flown regularly so the fuel wasn't old). The problem which had occurred on each of the previous flights went away and has not returned.
We run solely on Avgas now. Relatively fuel is cheap and accidents are expensive.

[9 lives]

As we were short on ideas it was suggested that we dumped the fuel

I think its been shown that the time to dump and refuel is about the same time required for carb ice to melt out...

In 4000 hours flying Mogas, I have never had a fuel type related event at all. O-200, O-235, O-320, O-360, O-470, O-520 all ran just fine on it - when flown in a type approved by STC.

[Jan Olieslagers]

The explosive power of the vapour from a few liters of gasoline is not to be underestimated! Do I recall right that this is the main reason to refuel as soon after landing as possible? Tanks empty => no danger, tanks full => limited danger, tanks part-full => high danger?

[ChickenHouse]

We ran a Contenental 0-200 on Mogas for years without any issues, then we developed a loss of power during climb out. The carburrettor had been replaced prior to the loss of power and eveything else checked out. I went flying with the pilot to see for myself. I wish I hadn't, it was very uncomfortable feeling as the engine sagged at 3-400 feet. I was very pleased when we got back on the ground. As we were short on ideas it was suggested that we dumped the fuel
(the aircraft was flown regularly so the fuel wasn't old). The problem which had occurred on each of the previous flights went away and has not returned.
We run solely on Avgas now. Relatively fuel is cheap and accidents are expensive.

Mogas or Autofuel? The first should have been no problem, but modern fuel for cars is a complicated issue. Even the standard Ethanol test does fail on certain car fuels, due to modern additives fetching chemical compounds - especially the high power versions. To be on a safer side with gasoline from a car station requires much more research then it used to be before.

[xrayalpha]

Away from avgas/mogas etc. and back to the OP:

The BBC article is well wrong.

The regs in the UK are very very complex, with some dating back to the 1920s.

A good, reliable summary is linked to from here:

Carriage and Storage of Petrol and Diesel | Regulations | Knowledge & Advice | Knowledge & Advice | RYA (http://www.rya.org.uk/knowledge-advice/regulations/Pages/carriage-and-storage-of-petrol-and-diesel.aspx)

As mentioned before, petrol stations can serve as little as the want - or not at all!

In many cases, to help stranded motorists and reduce staff training costs, they limit to one 5l plastic can. But that is usually their choice.

The 30l storage limit in a vehicle is for people who keep the stuff in their car: perhaps you live in a flat and can't keep it there and park on the street?

233l is quite a lot. We fill up to 10 20l jerry cans at our local supermarket. First, that is under the 233l. Second, the pumps stop at 100l and can only be used twice before you have to pay!

We spoke with the local petroleum officer before the petrol station opened, the supermarket's regional fuel manager on the day it opened (with the council chap standing with us) and the staff.

As the council chap said: we would rather have people who know what they are doing, doing it in a reasonable manner. At the self-service petrol pumps at midnight we have seen people on CCTV putting fuel in open buckets!

[Rod1]

I have been flying using mogas extensively for over 10 years. My LAA aircraft was one of the first to be cleared for use with E5 mogas (ethanol). I transport up to 3 X 20L cans in the boot. I would never use a leaky can and I use a purpose made siphoning tube. No issues, no problems, big cost saving. My alternative would be a 40 min round trip with a £14 landing fee to fill up with Avgas 91UL at about a 1/3 more per L. One word of warning, mogas in the UK is a very different product to the US.

Rod1

[Mariner9]

Mogas or Autofuel?

This has appeared on this thread from a couple of posters suggesting that the two are somehow different.

This is not the case. "Autofuel" (not an approved technical term but I presume meant to represent gasoline intended for petrol engined cars) is a Mogas (an approved technical abbreviation for motor gasoline). All Mogas (or autofuel if you really must) including unleaded and super unleaded gasoline sold on a forecourt in the UK must comply with the BS EN228 specification. That specification allows (but does not mandate) the presence of ethanol up to certain limits.

Certain airfields dispense ethanol-free Mogas, but that will also comply with BS EN228. Some Mogas sold from forecourts may also be ethanol free, but most isn't nowadays.

Aviation authorities appear to be losing the fear of ethanol at about the same rate as they are losing the fear of using GPS as primary nav.

[Chuck Glider]

The regs in the UK are very very complex, with some dating back to the 1920s.
They derive from a UN document, ADR, of which Annex A, Part 1, para 1.1.3.1 states:
Exemptions related to the nature of the transport operation

The provisions laid down in ADR do not apply to:

(a) The carriage of dangerous goods by private individuals where the goods in question
are packaged for retail sale and are intended for their personal or domestic use or for
their leisure or sporting activities provided that measures have been taken to prevent
any leakage of contents in normal conditions of carriage. When these goods are
flammable liquids carried in refillable receptacles filled by, or for, a private individual,
the total quantity shall not exceed 60 litres per receptacle and 240 litres per transport
unit. Dangerous goods in IBCs, large packagings or tanks are not considered to be
packaged for retail sale;

[patowalker]

The BBC article is well wrong.

Which is quite obvious from mistakes like

It must be kept in
a) in a shed
b) in a garage
c) Outside no more than six metres from your house - ie, at the end of a drive.

[Forfoxake]

Be aware that many petrol stations fuel tanks are contaminated with water and rust and are notorious for supplying contaminated fuel - and steel jerrycans are notorious for producing flakes of rust and paint as well.
As a result, make 100% sure, your fuel supplied from jerrycans into your aircraft is completely and thoroughly filtered through a funnel fitted with a mesh screen and a chamois.
I have never, repeat never, found any contamination in any car fuel that I have obtained (mainly in the UK) to use in my Rotax-powered aeroplanes in over 20 years. Nevertheless, I do try to stick to the LAA recommendation to use fuel from high turnover outlets (mainly supermarkets recently). On the other hand, it was common to find water in the Avgas obtained from the bowser when I flew Cessna 150's etc.

However, I have often found paint flakes from the inside of metal Jerry Cans which is why I always filter the fuel into the tanks. I find Mr Funnels excellent.

I appreciate that there is a very small risk of vapour igniting when it is poured into the tank (particularly on cold, crisp and dry winter days) which is why I use conductive cans and funnels. The LAA has a leaflet that outlines how you can overcome this risk by connecting together the can, funnel and aeroplane and earthing the lot.

Incidentally, ROTAX engines are specifically designed to run on unleaded petrol and I have never had any problem running them on this, even with the recent introduction of 5% alcohol in unleaded (although I understand that this has caused big problems in some fibre glass tanks). Also bear in mind that it is much easier to fuel from cans when you are only using 10-15lph rather than 25-35lph!

Having said all this, I now also have a share in a Lycoming powered aircraft and we have to travel to nearby airfields to pump in Avgas and keep a few cans at base for emergencies.

[kevkdg]

Thanks for all the replies.

Does the likes of "super unleaded" as opposed to standard unleaded generally contain less ethanol?

[9 lives]

Aviation authorities appear to be losing the fear of ethanol

The fear of ethanol is based upon chemistry (which won't change with time). Ethanol is chemically incompatible with some fuel system components and can cause corrosion in others. Enough ethanol blended into gasoline will also affect the energy density of the fuel (so it runs lean). When I flew the ethanol fueled C 150 (modified for the role), it was weird to see a fuel flow exceeding 15GHP on takeoff!

[RatherBeFlying]

At our field in Canada, we go to a nearby airport to pump avgas into drums, 205 l. With 4 drums to fill they appreciate our business.

[Maoraigh1]

Almost all my 43 hours flying in 2016 were on Tesco EN228, in an O200. Avgas was only used when refuelling away from home. The fuel tested alcohol free.
I recall the regulation on how much you can carry is EU, and is huge - 205L for your own use. Until Brexit.

[Forfoxake]

Thanks for all the replies.

Does the likes of "super unleaded" as opposed to standard unleaded generally contain less ethanol?
For a while after 5% ethanol was added to all standard unleaded in Scotland, I found that super unleaded from eg. Esso did not contain any alcohol and was soon approved by the LAA in aeroplanes permitted to use unleaded petrol. However, a couple of years ago 5% ethanol appeared in super unleaded too, at least in the west of Scotland. I presume it is now the same in most of the UK which is why, with certain precautions and in certain engines, use of standard unleaded with 5% ethanol can now be approved in LAA aircraft. Strangely, however microlights with the same engines and similar or identical fuel systems were permitted to use unleaded petrol containing ethanol throughout.

[onetrack]

Remember that ethanol will attack any natural rubber, plain plastic or fibreglass components in fuel systems and damage them.
Fuel system components need to be made from ethanol-resistant materials when using fuels with ethanol in them.
Ethanol also strips rust, varnish, and gums from inside fuel tanks and fuel systems and this debris can block fuel lines, filters and small orifices in components such as carburettors.

[ChickenHouse]

Due to the EUs unrestricted subintellectual green ideology warfare it is disputable whether the usual Autofuel STCs cover some of the current car gas station fuels. Typically the STC is issued on the basis of EN228, version of February 1999, but the eurocrats changed that to also put food and edibles in our tanks with EN228:2004 and EN228:2008.

Oil companies fight the bad chemical behavior of such mixed substances by restricting storage of fuel to 90 days after tap and adding additives, of which some fetch water and ethanol, thus rendering our basic ethanol tests virtually useless -> if you don't see a separation on the water test, it does not necessarily tell you there is no ethanol! Whether the water and ethanol fetched by additives is doing harm to the use in aviation is totally unclear.

[Shoestring Flyer]

Yes. Most 'ordinary' unleaded in the UK contains ethanol.
With 'Super unleaded' less so dependant on which part of the country you are in and which make fuel you use. Any Mogas you use in an LAA Permit aircraft needs to conform to EN228. Esso 'Super unleaded' conforms to EN228 and in the Midlands contains no ethanol currently if distributed from Kingsbury distribution centre, near Tamworth, to the petrol stations.
Ethanol is added, or not added, at the distribution centres around the UK and can vary depending on your location and make of fuel used. So your location can make it a lottery if ethanol is added or not to any fuel you may buy!

[kaitakbowler]

As to containers, had one of these for the boat, expensive but so is dirty fuel in the long run, and shared in a group a/c not so expensive.

Flo N' Go Duramax 53L Wheeled Fuel Transporter - Marshall Industrial Supplies (http://www.marshallindustrial.co.uk/flo-n-go-duramax-53l-wheeled-fuel-transporter/).

Paul M

[kevkdg]

could order from states quite a bit cheaper


Scepter 06792 Flo N'Go DuraMax 14 Gallon Transfer Fuel Caddy Gas Can | eBay (http://www.ebay.co.uk/itm/Scepter-06792-Flo-NGo-DuraMax-14-Gallon-Transfer-Fuel-Caddy-Gas-Can-/331857016569?hash=item4d443836f9:g:p9UAAOSw~oFXOSxN)

[Mariner9]

The fear of ethanol is based upon chemistry (which won't change with time).

Actually it has and will continue to do so. There is loads of research being undertaken by the oil companies and bodies such as ASTM, EI etc concerning the chemistry of ethanol in fuel which has greatly increased our understanding. Furthermore bodies such as the LAA and EAA are looking into the aviation aspects of the fuel. Regulations and recommendations concerning use of Mogas in aircraft are changing, albeit slowly. Rod1 commented above that his aircraft has been cleared to run on E5 which is a perfect illustration of this point.

Oil companies fight the bad chemical behavior of such mixed substances by restricting storage of fuel to 90 days after tap and adding additives, of which some fetch water and ethanol, thus rendering our basic ethanol tests virtually useless -> if you don't see a separation on the water test, it does not necessarily tell you there is no ethanol! Whether the water and ethanol fetched by additives is doing harm to the use in aviation is totally unclear.

That post, with respect, is typical of many on Pprune concerning ethanol, which routinely contain an eclectic mix of facts, myths, half truths, and faulty conclusions therefrom. Water and ethanol fetching additives? There are additives (IPA) that can deal with low level water contamination but those are in fact approved for use in aviation fuels including Avgas 100LL. Thus, the affect is not "totally unclear" Furthermore, its extremely rare to find IPA in Mogas (if you do its unlikely to contain ethanol for reasons I won't bore you with.)

There are no additives that "fetch" ethanol (though if you added enough water to a tank you could remove the ethanol from the fuel though I'd hardly class water as an additive).

The only part I sort of agree with is that a fuel that passes the separation test (note it was not designed as an an ethanol test though it can be an indicator of ethanol) may still contain ethanol. I again take issue with the "totally unknown affects" opinion though.

FWIW, I'm happy to use Mogas with or without ethanol subject to the following:

The aircraft doesn't have ethanol compatibility problems in fuel tank and lines.
The aircraft doesn't suffer from water ingress into the fuel tanks during rain
I'm not intending to fly hot and/or high.
The regulations allow me to do so.

M9 (Investigates fuel quality issues for a living and regularly flies on E5 Mogas)

[Geriaviator]

It's a very long time (45 yrs) since I was one of many owners taking part in the BGA trials of Mogas, in those days Four Star and leaded. We found that four-star made for a cleaner engine, while automotive multigrade oil gave far easier starting in winter and constant oil pressures instead of the sky-high when hot, very low when cold of Aeroshell 80/100. This was proven in countless aerotows mostly with Gipsy Major and Lycoming engines.

Today I'm years out of touch, and maybe today's unleaded motor fuel is not so prone to vapour locking. Our old-fashioned and doubtless dangerous demo was to pour a capful of Avgas on the concrete with a capful of Mogas beside it; the Mogas evaporates in seconds, the Avgas stays damp for much longer. If the fuel pump is attached to the hot crankcase the fuel may vapourise, resulting in a sudden silence. I demonstrated this in a VW-engined ultralight to great effect; every morning my faint scars remind me of rearranging the dashboard in the ensuing forced landing. After my 40 stitches were removed I went back to Avgas.