Opinion on Mogas STC

[QDMQDMQDM]

Looking at touring in Italy next year and there are a lot of strips with Mogas, very few with avgas. Would be great to get the PA18 approved on Mogas.

Has anyone got experience with Mogas STCs or running Mogas? Vapour lock is my big concern, but the guys over at supercub.org are universally positive and the Petersen's website says:

<<
CERTIFICATION
All of our engine STC approvals are based on 150 hour ground endurance runs. A total of 105 hours is conducted at rated sea level power, (full throttle - 100% power) with the remaining 45 hours conducted at various throttle settings from 60 to 85 % power.

Extensive detonation testing is conducted prior to the endurance testing to establish the engine's ability to function without damage and to develop rated power.

Airframes are tested against vapor lock by conducting flight tests to a minimum of 12,500 feet. The first series of tests is conducted on high volatility winter blend fuel which is heated in the wing to 85 degrees before takeoff and climb. The second is conducted on winter blend fuel heated to 110 degrees prior to takeoff and climb. Any loss of power or excessive fuel pressure loss during these tests results in a failure of the test. Extensive fuel flow tests are also conducted on airframe fuel systems to insure adequate fuel flow.>>

[White Bear]

QDMQDMQDM,
(I hope the U.S. autogas STC, and your STC for Mogas is essentially the same, STC.)
I own a ¼ share of a 1958 172 with a Continental 0200 that has the ‘autogas’ STC. It has flown for years on autogas with absolutely no engine, carburetor, fuel line or fuel tank problems.

There is an AD requiring the fuel tank selector to be marked, to the effect that over 6000 ft the left or right fuel tank must be selected. A little research showed that apparently there were some issues with vapour lock that going to one tank solved, hence the AD, although I have flown it as high as 10,000ft with any problem at all.

In the U.S. among a certain group of flyers, the autogas STC is considered a very desirable thing. Aside from the AD, and that only requires a placcard, I am not aware of any other problems with using autogas.
Hope this helps.
Regards,
White Bear.

[Mariner9]

What's the Peterson website address QDM? Would be interested in having a look.

I not the temperatures quoted are in deg F, which implies its a US site, and presumably did the tests on US Mogas.

Loads of different Mogas specs in the US, and they differ from season to season and from State to State. Ours in the UK are different again, and also different to those in the Italy, (Italy, with high ground and high ambient temps require low vapour pressure fuels) which prolly accounts for their increased use in a/c over there.

Nerd mode on::8 : Vapour lock likelihood can be done by calculation, but its a bit of a black art, and depends on a large number of factors including:

Fuel vapour pressure
Fuel density
Fuel temperature
Fuel pump type
Suction head (distance top of fuel to bottom of pump)
Length & diameter of fuel piping
Fuel flow rate
Pressure altitude

[Brooklands]

QDM,
There's information about operating on mogas on the caa site (http://www.caa.co.uk/default.aspx?categoryid=224&pagetype=90&pageid=630) including which aircraft are approved
Brooklands

[QDMQDMQDM]

Thanks for all opinions and thoughts. It seems to be no problem in the US and a lot more caveats over here. The business about a 20 deg C limitation is impossible in practice. How much of a problem really is vapour lock in a gravity feed system such as a PA18?