M15

M15 is a motor fuel consisting of 85% unleaded gasoline and 15% methanol by volume. It is used in standard petrol engines with no modification to fuel system or engine management required, distinguishing it from higher methanol blends such as M85 or E85 ethanol blends, which demand fuel-compatible fuel injectors, seals, and tank linings.

Methanol is a polar alcohol with a lower energy density than petrol, roughly 21 megajoules per kilogram compared to petrol's 44. This means M15 delivers approximately 3 to 4 percent less energy per litre, requiring slightly richer fueling maps in some engines to maintain power output. However, methanol has a higher octane rating, typically around 106 RON, which allows engines to run higher boost pressures or compression ratios without knock.

The primary advantage of M15 in markets where it is available, such as Brazil and parts of Europe, is its lower cost and reduced carbon emissions compared to straight petrol. Methanol is produced from synthesis gas, which can be derived from natural gas, coal, or biomass, making fuel supply more flexible than crude oil dependency. M15 reduces tailpipe carbon dioxide by approximately 5 to 10 percent depending on methanol feedstock.

Compatibility and maintenance issues are real. Methanol is hygroscopic, absorbing water from air and tank headspace; fuel systems must include water removal cartridges or corrosion inhibitors to prevent phase separation and rust in fuel tanks and injectors. Long-term storage of M15 in sealed containers is more difficult than petrol because methanol can degrade elastomeric seals and corrode ferrous fuel system components if proper corrosion inhibitors are not present.

M15 remains relatively niche outside specific regions because refineries and distribution networks are built around petrol and diesel, and consumer vehicles in most markets lack labelling or owner familiarity. Government subsidies and blending mandates in Brazil and parts of Scandinavia have driven adoption there, but adoption elsewhere remains limited by refueling infrastructure and lack of engine warranty coverage from manufacturers.