The best and simplest mixture is 80% methanol and 20% castor. Adding about 3% acetone is supposed to be similar to having around 5% nitro as far as starting and idling go but it's not necessary. Your standard car engine will run quite well on this simple mixture. Seeing you're in Portugal you should be able to get Castrol M castor, it's absolutely the best you can buy. Here's a start.

Name: Castrol Portuguesa
Address: Lagoa's Park - Edificio 3 2740-244 Porto Salvo Oeiras, Portugal
Phone: 00 351( 21) 389 1000
Fax: 00 351( 21) 389 1600

Raising the compression enough to get the most out of straight methanol isn't all that simple though because it requires some machining of the cylinder head and accurate measuring equipment. Most engines (including cars) are around 9.5:1 and you need to get it up to about 13:1 for best performance with zero nitro.