There’s Research Octane Number (RON), Motor Octane Number (MON), and Antiknock Index. RON is roughly 10 higher than MON for the same fuel. AKI is the average of the two. AVGAS has a MON of approximately 100. Autofuel octane rating in europe is normally given as RON. So 100 octane autofuel has approximately a MON of 90.
In an emergency, it’ll all burn – but you need to be careful long term.
On some aircraft, the mogas STC is paperwork only – nothing actually changed on the aircraft.
Nuff said…
EN228 is the specification of UK regular filling station fuel. The CAA Safety Sense leaflet (number 4) said a mixture of Avgas and Mogas with over 25% Mogas would be considered Mogas. Max operating altitude 6000’, and tank temp not above 20°.
Max operating altitude 6000’, and tank temp not above 20°.
Surely those two figures (especially the 2nd one) would make Mogas practically useless.
So 100 octane autofuel has approximately a MON of 90.
What is the petrol normally sold in N Europe? Or is there a variation in that too? In the UK we have standard unleaded petrol, and then there are various brand-dependent “super” versions which most people never use.
Yes, but this “restriction” is a UK invention. No such thing in other countries.
I could dig around but I am going to bed now 
Mogas is supposed to be good for (from vague memory) about 14000ft. That, of course, is no good for many pilots.
Fuel systems can be designed to use Mogas to much higher altitudes but I don’t think many planes have them.
Maybe somebody will know the details?
Fuel systems can be designed to use Mogas to much higher altitudes but I don’t think many planes have them.
Maybe somebody will know the details?
I know that it works much higher up. Those are all arbitrary theoretical numbers, usually not backed by anything. These 1950s tractor engines really aren’t particularly picky when it comes to fuel.
The CAA Safety Sense leaflet (number 4)
Max operating altitude 6000’, and tank temp not above 20°.
Isn’t that only when it contains alcohol, of which in the UK it’s mixed whether it does or not.
Yes, but this “restriction” is a UK invention. No such thing in other countries.
Well, actually there was a time around 1990 where different taxes in Swden made MOGAS very much cheaper than AVGAS. At that time MOGAS was extensively used and the Swedish CAA published the same restriction Maoraigh quoted.
Well, at least the 6000 ft limit was the same. There was a temperature limit as well, but I don’t remember if it was exactly 20°C. In any case either restriction could be lifted by performing a test flight to the desired altitude and with the desired tank temperature to demonstrate that no vapor lock occurred.
one of the main problems is alcohol that is sometimes mixed into the fuel so the best way is to check it before either
or with a any other clear plastic bottle just need to mark the waterlione before and compare
Alcohol sometimes can affect rubber in fuelhoses, carbs, etc so that could be a an issue
in germany you can buy 102 octane unleaded fuel with no Ethanol mix into the fuel
cessna 182P with o-470s is only a “paper” stc for mogas (but mogas is without Ethanol!!) Ethanol can be agressive to fuellines tanks etc, anyway it is better to use teflon inner tube aeroquip lines (lighter, non smelling as they are noth “breathing”, but a bit more careful to handle when it comes to bends etc due to kinking possibilities)
