Well, this is one of the most difficult levels. The starting conditions are too bad and it's impossible to build up a defence. The enemy has three well-positioned oil rigs and you have two with very low oil and one oil patch pretty far. So, if you don't krush the mutants in the first 5 minutes, you'll loose in the next 10-15 minutes. This is how I did it finally (after 6 unsuccessful attempts).
Group all infantry and 1 ATV from the starting force (group 1) and move them to the south-western corner of your camp. Build a research lab and power plant to the north and an oil derrick. Group all other vehicles (group 2) and move them to the north oil patch. After group 1 is attacked, move it to the west and through the bridge. Attack a monster truck and gunnest and destroy the mutant oil rig. Build some swat and send them to reinforce group 1.
Meanwhile, upgrade the machine shop to get flame ATVs and build as many as you can. Move group 2 to the north and then to the north-western edge of the map. You'll see a grapeshot tower to the south-west. Don't attack it, go past it by the northern edge of the map and krush the oil rig. Send flame ATVs to reinforce group 2. Krush the near-by power plant and destroy any derricks the mutants are sending to the oil patch. Then start building up and upgrading.
Build as many flame ATVs as possible and send them to group 2. In 5-10 minutes after the oil runs out, switch both tankers to the nothern oil rig. The enemy will constantly try rebuilding derricks and power plants, so destroy them with ATVs. Don't attack the tower since there are pretty many of them and you need a really large force to succeed. Build 5-6 tanks and 30 swat and attack the towers to the west of the northern oil rig. Destroy the third mutant rig and finish 'em up. At the beginning you have to be very, very fast!