Auto Fuel

Opposition to Auto Fuel

Auto fuel vs. avgas

Octane

From:

 "Light Plane Maintenance"

avgas vs. autogas 

Aviation gasoline (avgas)

High-quality gasoline manufactured under stringent controls to meet the rigorous performance and safety requirements of piston-type aircraft engines. Volatility of aviation gasoline is closely controlled since, in most aircraft engines, excessive volatility can lead to vapor lock. Aviation gasolines generally have lower vapor pressure and a narrower distillation range than automotive gasolines (see distillation test). Aviation gasolines are formulated to resist chemical degradation and to prevent fuel system corrosion. There are two basic grades of aviation gasolines (based on their antiknock value): 80 (80 lean/87 rich) and 100 (100 lean/130 rich). Aviation gasoline has different properties than turbo fuel, which fuels gas-turbine-powered aircraft.

Article from Texas Skyways web site

http://www.txskyways.com  

UL 91/96 gets cool reception

Use of Motor Gasoline in Aircraft Engines

The question of whether light aircraft engines can be operated on automotive fuel is often raised. It is,

however, a practice that is discouraged and even forbidden by most engine manufacturers, the fuel suppliers

and government regulatory authorities. Some of the reasons for this are as follows:

1. Motor gasoline has different distillation characteristics than aviation gasoline. Mogas includes heavier

petroleum fractions which tend to include hydrocarbons less stable to oxidation, less clean-burning,

more prone to form combustion chamber and induction system deposits.

2. Motor gasoline normally has much higher vapour pressure, which varies seasonally. With a high RVP

fuel the risk of vapour lock during takeoff and climb increases, particularly if the aircraft has been

parked in high ambient temperatures and does not have a gravity-fed fuel system.

3. Motor gasolines may contain many different types of additives not permitted in aviation gasoline.

There is no consistency or control on mogas additives between different suppliers. Aviation gasoline,

regardless of where it is manufactured or purchased, is limited to certain specific additives.

A purchaser intending to use motor gasoline in an aircraft would have no knowledge of the physical

properties or composition of the gasoline being supplied. It will vary markedly on a seasonal basis and by

geographic region. Octane quality can only be known approximately and can also vary substantially

between grades and suppliers.

Although there is STC's available that allow use of auto fuel per the instructions and guidelines of the STC instructions. It is not the wisest choice to run this type of fuel in the Bonanza for several reasons.

TCM Technical Brief T93-5

Read up on the fuel specifications:

ASTM D910 for aviation gasoline

ASTM D4814 automotive gasoline