What is the best fuel (Mogas) for your engine

[Old Koreelah]

One aspect possibly overlooked when topping up tanks with fresh Mogas: if there’s still fuel in the float bowl(s), that’s got to spark up first, before the fresh stuff gets drawn in.

 

Regarding reliable suppliers of Mogas: we’re lucky to have a local servo managed by a young bloke from a respected family, who knows how important it is for us to keep dodgy stuff (including ethanol) out of our aeroplanes. His brother trained as pilot and he makes sure there’s always a range of aviation oils on his shelves.

That gives me confidance in his 98 Mogas.

 

 

[turboplanner]

1 hour ago, walrus said:

Between starts? One - two weeks.

95 RON

I wouldn't expect you to have start problems with 95, however:

Depending who supplies it can have ethanol in it, and you don't want ethanol gumming up air passages and eating components, so you need to have the guarantee there's no ethanol. If ethanol gums up an air passage which has been plugged during manufacture (ie no screw at end) - you can finish up having to throw away the carby. I've been caught on a couple of engines.

 

98 RON 

For starting within two weeks I wouldn't expect you to have a problem because that's the threshold where the problem starts.

That's based on Start 1: start with new fuel, Start 2: start with Start 1 fuel then refuel, or refuel before Start 3 (fresh fuel again).

If you are getting starts with fuel older than two weeks you can join my club where some engines will become difficult to start, four weeks fuel-injected Chev 350 doesn't fire, some engines (60 year old Ferguson with Standard engine) fire instantly.

[turboplanner]

1 hour ago, Old Koreelah said:

One aspect possibly overlooked when topping up tanks with fresh Mogas: if there’s still fuel in the float bowl(s), that’s got to spark up first, before the fresh stuff gets drawn in.

 

 

I've found it doesn't take the full bowl.

I've had four or five attempts with no sign of a fire up, then realised the inevitable, put some fresh fuel into the tank, waited five minutes or so, come back and first turn of the starter get a fire up, then dies but second starter attempt fies up and runs.

[Cosmick]

On 05/11/2021 at 7:37 AM, Cosmick said:

Rotaxservice.com -  The Rotax 912 A/F/UL engines require a minimum octane rating of 87 AKI, commonly referred to as “regular” while the Rotax 912 S/ULS/ULSFR and 914 F/UL require a minimum of 91 AKI (“premium”).

Reviewing again the Video I listed earlier and referring to the Rotax requirements I notice the Octane measurement used is AKI which according to the 'Man in the Video' is 4 points less than RON so 87 AKI is 91 RON and 91 AKI is 95 RON.

[Flightrite]

Having worked for a fuel Co for 13 years you guys would be mortified at what goes where😉 I’ve run Mogas ( all varieties) on my low HP donks and 100/130 (now 100LL) in my high HP donks, a Mr Funnel used whenever possible, never had an issue and I sleep well at night😉.

[onetrack]

One must always keep in mind that when using automotive fuels from servos, the older underground tanks are steel, coated with bitumen. After 20 years, the high levels of moisture in the soil, that is carrying either acidic or alkaline components in solution, gets under the bitumen and corrodes the steel. This then develops into pinholes in the steel tanks, which allows entry of dirty, rusty water, which settles on the bottom of the tank.

 

Even though the suction spears for the bowser pumps are placed a distance from the bottom of the tank, swirling fuel from recent underground tank fills, makes the dirty rusty water move within reach of the suction lines for the bowser pumps, thus pumping up the rusty dirty water with the fuel. The filters on the bowsers are only mesh screens (about 20 or 30 micron from memory), they do not have elements than can stop water.

 

Many older servos also have fill points for underground tanks that are poorly positioned and poorly designed, and which can allow floodwaters to enter tanks.

 

So the chances of acquiring petrol contaminated with dirty rusty water, particularly from older servos, are reasonably high. Cars and trucks have better fuel filtering than bowser pumps, so they stop a lot of this crap from reaching your car or truck engines critical fuel components.

 

Newer servos utilise fibreglass tanks, and are better designed, so the chances of corrosion and contamination are greatly reduced. Most servos have fuel leak tracing spears sited in the ground around the tanks. but these are designed to catch fuel leaks into groundwater aquifers, and they're behind the curve when it comes to fuel contamination, as they only catch holes in tanks when there's a serious outflow of fuel from the tank into the soil.

 

There's a reason why avgas is delivered in sealed containers with strict traceability. Automotive fuels have multiple points of entry for contamination and adulteration. More than one dodgy servo owner/operator has been done for fuel adulteration, adding a number of cheap, readily available, discarded industrial chemicals, ranging from products such as toluene, discarded parts cleaning fluids, to paint thinners. 

 

If you must buy petrol for your aircraft from servos, buying from the newest servos is critical, buying from large company-owned servos means less chance of servo owner fuel adulteration - but you still must be aware that fuel companies can add ethanol in any percentage up to 10% in 91 RON automotive fuel, without advising users.

 

https://www.fcai.com.au/environment/can-my-vehicle-operate-on-ethanol-blend-petrol

[skippydiesel]

14 minutes ago, onetrack said:

One must always keep in mind that when using automotive fuels from servos, the older underground tanks are steel, coated with bitumen. After 20 years, the high levels of moisture in the soil, that is carrying either acidic or alkaline components in solution, gets under the bitumen and corrodes the steel. This then develops into pinholes in the steel tanks, which allows entry of dirty, rusty water, which settles on the bottom of the tank.

 

Even though the suction spears for the bowser pumps are placed a distance from the bottom of the tank, swirling fuel from recent underground tank fills, makes the dirty rusty water move within reach of the suction lines for the bowser pumps, thus pumping up the rusty dirty water with the fuel. The filters on the bowsers are only mesh screens (about 20 or 30 micron from memory), they do not have elements than can stop water.

 

Many older servos also have fill points for underground tanks that are poorly positioned and poorly designed, and which can allow floodwaters to enter tanks.

 

So the chances of acquiring petrol contaminated with dirty rusty water, particularly from older servos, are reasonably high. Cars and trucks have better fuel filtering than bowser pumps, so they stop a lot of this crap from reaching your car or truck engines critical fuel components.

 

Newer servos utilise fibreglass tanks, and are better designed, so the chances of corrosion and contamination are greatly reduced. Most servos have fuel leak tracing spears sited in the ground around the tanks. but these are designed to catch fuel leaks into groundwater aquifers, and they're behind the curve when it comes to fuel contamination, as they only catch holes in tanks when there's a serious outflow of fuel from the tank into the soil.

 

There's a reason why avgas is delivered in sealed containers with strict traceability. Automotive fuels have multiple points of entry for contamination and adulteration. More than one dodgy servo owner/operator has been done for fuel adulteration, adding a number of cheap, readily available, discarded industrial chemicals, ranging from products such as toluene, discarded parts cleaning fluids, to paint thinners. 

 

If you must buy petrol for your aircraft from servos, buying from the newest servos is critical, buying from large company-owned servos means less chance of servo owner fuel adulteration - but you still must be aware that fuel companies can add ethanol in any percentage up to 10% in 91 RON automotive fuel, without advising users.

 

https://www.fcai.com.au/environment/can-my-vehicle-operate-on-ethanol-blend-petrol

With reference to your Ethanol comment: Unlikely from major distributers. Why ? because they advertise E10/(10%) as a distinct product, separate from their non ethanol blended petrol. Why would they jeopardise their customer trust when there are other competing brands only to happy to take disgruntled ex customers.

 

Adulteration stories have been around for just about ever - rarely is their proof that the bigger more reputable companies do any such thing. Smaller "independents" well that's something else.

 

At the end of the debate, it is still Rotax recommendation that ULP/MoGas/Unledade is the preferred fuel.

[facthunter]

Companies don't  always use their own tankers. Others get diverted when there's a supply issue. Nev

[spacesailor]

Starts between fill !.

I, like lots of other car owner,s have Not refueled my Pajero for getting on to a year now. Running a second ( diesel  ) car.

The Old  95 octane fuel must be due for a change soon.

Here,s hoping it Will start when that day eventually arrives, then off for holidays AND breakdowns.

I,m going out to check the logbook.

I,m back, the last fill was' 15 / 2 / 21 at Orange.  Price was $ 131.9 cpl.

spacesailor

Edited November 7, 2021 by spacesailor
More added

[jackc]

Geez, after all this I am probably not game to buy Mogas  from anywhere for my plane 🙂 

[onetrack]

I'm not saying you shouldn't buy automotive petrol (mogas is an American term that shouldn't be used here). All I'm saying is, be aware of the potential dangers in using a product that has no traceability, and is susceptible to all kinds of unauthorised and unforeseen inputs. There are plenty of recorded cases of motorists suing servos for damage to their vehicles engines and fuel systems by contaminated fuel. It pays to keep receipts and good records of your fuel purchases.

 

As kgwilson points out, you buy fuel from a servo that is not a low-volume retailer with tanks that are 20-30 years old, and you buy from a retail outlet that is company-owned, so the risk from adulteration designed to increase profits is very low.

 

Around 80% of our automotive petrol is refined in Singapore, to Australian Fuel Standard Specifications, it's shipped in in large volumes in big ocean-going tankers, and it's distributed via bulk tanks to all the various company branded outlets.

The companies who own the bulk fuel farms are not necessarily the oil companies, it's a standalone business by itself, just storing fuel in bulk. 

The oil companies draw the fuel from the bulk tanks with their company road tankers or contracted fuel road tankers, and "additive packages" are added at the point of filling the road tankers, so they deliver a specific product to the company servos.

 

As you all know, the oil companies specialise in branding their petrol (and diesel) products as being "different and better" to the other companies products, the only difference is whether a fuel additive package is added to the bulk petrol, or not.

[turboplanner]

26 minutes ago, jackc said:

Geez, after all this I am probably not game to buy Mogas  from anywhere for my plane 🙂 

Some of this is BS. It's very straightforward; you get the recommendation straight from your engine supplier, never from "the man in the video".

[turboplanner]

7 minutes ago, onetrack said:

I'm not saying you shouldn't buy automotive petrol (mogas is an American term that shouldn't be used here).

Agree; Mogas is a name applied to gasoline refined in the USA

It comes in three standards:
Regular: 87 octane

Midgrade: 89-90 octane

Premium: 91 - 94 octane

Octane rating is to the US standard.

That might make some better sense to any US owner reading this thread

 

Australia

Australian petrol is refined in Australia and overseas to the varieties we have been discussing.

Use only the petrol recommended by your engine manufacturer.

What some of us had been discussing on another thread, and this one were the traps to can be caught with when buying different grades of petrol.

It's not such a problem if the engine simply won't start, but if you start changing things or airways become gummed up, you can't just roll to the side of the road; you're going to be faced with a forced landing, perhaps an EFATO and you have to pull that off. Better to talk to your manufacturer.

[onetrack]

There were 670 recorded cases of fuel contamination in 2015, where motorists lodged a claim. This is only the number who decided to proceed with a claim against the servo operator.

There were likely to be a lot more, who did receive contaminated fuel, but who did not proceed with a claim against the servo operator, because the damage was minimal, or they wore the cost, and decided it wasn't worth the effort to pursue a claim.

 

https://www.choice.com.au/transport/cars/maintenance/articles/contaminated-fuel-costing-drivers-thousands-of-dollars-in-repairs

 

https://www.choice.com.au/transport/cars/maintenance/articles/petrol-stations-selling-contaminated-fuel-customers-with-repair-bills 

 

Admittedly, the number of fuel contamination cases is low, as a proportion of the total number of fuelling-up operations annually - but the risk is still there, it simply pays to exercise caution.

[BirdDog]

For what it's worth I have been running 95 on my 912ULS engines for the last 5 years, and never had an issue.  I mainly use CALTEX, but there is now a brand new servo next to the AD which sells 95, so I use it.

 

I always do a fuel drain, etc, and makes sure no water etc has come along for the ride.

 

I use AVGAS when I have to, but not often.

[walrus]

Mr. Funnel is your friend.

[rgmwa]

I had ten litres of water removed from my tank a few years ago after filling up at my regular servo. Luckily it was the car's tank and not the plane's. The servo paid for getting the car fixed, and told me I was the 5th customer who didn't drive too far that day, so they were expecting a phone call. Never been back since.

I used to run the plane on BP Ultimate 98, but have since switched to 95 as I once found some gummy residue on the gascolator screen during an annual after not flying for a two-three months.  

 

[Flightrite]

Plenty of STC’d Lyc’s & Conty’s use Mogas, only issue I have found over the years is with vapourlock, other than that Mogas is the go👍

[walrus]

The fuel circuit in a 912 iS includes dual redundant pumps, an 8 micron filter after the 40 odd micron gascolator and its pressurised when running to about 45psi and a flow rate of about 70 l/h ( > 2X maximum flow). There is no air access to this system, the only air contact is on the free surface in. the fuel tanks. Murphy’s law therefore suggests some new failure mode will apply one day instead of “gum in carburettor passages”. 😞

[turboplanner]

49 minutes ago, walrus said:

The fuel circuit in a 912 iS includes dual redundant pumps, an 8 micron filter after the 40 odd micron gascolator and its pressurised when running to about 45psi and a flow rate of about 70 l/h ( > 2X maximum flow). There is no air access to this system, the only air contact is on the free surface in. the fuel tanks. Murphy’s law therefore suggests some new failure mode will apply one day instead of “gum in carburettor passages”. 😞

.

 

Edited November 7, 2021 by turboplanner

[turboplanner]

1 hour ago, walrus said:

The fuel circuit in a 912 iS includes dual redundant pumps, an 8 micron filter after the 40 odd micron gascolator and its pressurised when running to about 45psi and a flow rate of about 70 l/h ( > 2X maximum flow). There is no air access to this system, the only air contact is on the free surface in. the fuel tanks. Murphy’s law therefore suggests some new failure mode will apply one day instead of “gum in carburettor passages”. 😞

I've set out the various phases to show where the main ethanol blockage problem occurs (other than eating the lines/tank etc)

 

Carburettors – Slide type 

The following is a description of how a generic slide type carburettor handles mixture for the various rpm phases.  Disclaimer: Refer to the Workshop Manual for your carburettor – they can vary in design.

 

Each RPM phase is handled by a different section of the carburettor.

This is generally the order you for setup or re-tune a slide carby.

 

Phase 1. Wide open throttle

Mixture controlled by the main jet when the slide is fully open.

Mixture is varied by altering the Main Jet size.

 

Phase 2. Idle, Slow running

Mixture controlled by Pilot adjusting screw, which on some carbies alters air, others fuel

(a)   It can be compromised by adjusting the throttle cable stop down too far, making that the pilot jet.

(b)   It can be compromised by a blocked slow running mixture hole on the engine side of the throttle. Where blocked by ethanol residue, slow running galleries can be cleaned out by removing the jet screw from one end and punching out the cap at the other end of the gallery. However, some slow running galleries are sealed off during the manufacturing process and the carburettor/body needs to be replaced.

 

Phase 3. About quarter to half throttle

Mixture controlled by the cutaway or bevel on the side of the slide barrel opposite from the engine.

Adjustment can be cut, or slides fitted – 1.5 mm increments.

 

Phase 4. Approx. three quarter throttle

Mixture controlled by the taper needle in the throat

Adjustable by grooves and circlip

[jackc]

Turbs, this would lead me to believe that addition of injector cleaner would be a help to keep carbides clear of any residue forming?

Edited November 7, 2021 by jackc
word change

[BirdDog]

1 hour ago, walrus said:

The fuel circuit in a 912 iS includes dual redundant pumps, an 8 micron filter after the 40 odd micron gascolator and its pressurised when running to about 45psi and a flow rate of about 70 l/h ( > 2X maximum flow). There is no air access to this system, the only air contact is on the free surface in. the fuel tanks. Murphy’s law therefore suggests some new failure mode will apply one day instead of “gum in carburettor passages”. 😞

My Rotax 912 has a fuel pressure of about 5PSI and a flow rate of 22Lph at wide open and full pitch. 
 

I don’t know anyone that has had issues running Mogas in their 912s. The flight school where I learnt to fly ran mogas in all their machines for years - never had a problem.  
 

like anything we do in aviation, sure there is always a risk, but the stats show they are low, in my opinion. 

[turboplanner]

3 minutes ago, jackc said:

Turbs, this would lead me to believe that addition of injector cleaner would be a help to keep carbides clear of any residue forming?

I didn't have any success down that path, probably because injector cleaner works while it runs through with the flow; the ethanol residue builds up while the engine's idling. Where you can open up both ends of the gallery and scrape it out or blow it out with compressed air it's just a small maintenance problem, it's the hidden gallereries that are the PITA, fixed with a new carbie or making up a manifold and putting a different carbie on.

[turboplanner]

3 minutes ago, BirdDog said:

My Rotax 912 has a fuel pressure of about 5PSI and a flow rate of 22Lph at wide open and full pitch. 
 

I don’t know anyone that has had issues running Mogas in their 912s. The flight school where I learnt to fly ran mogas in all their machines for years - never had a problem.  
 

like anything we do in aviation, sure there is always a risk, but the stats show they are low, in my opinion. 

People are starting to drift off the issues.

I would not expect any school running 98 petrol to have any problems other than getting cancer from handling it.