Mineral oil-based 5W-30 will also increase your HP -- at least in lower temperatures (short trips). On long highway trips where the oil get up to full temp you wont see as big an improvement over regular 10W-30 oil

Datsun approves of 5W-30 for a-series engine (see Engine Oil Specifications). Can the synthetic can be run even during summer?

Synthetic also lasts longer, while mineral oil breaks down after 5000 miles or so