66 Chapter 4 — Your Driving • Abrupt starts and hard stops can increase fuel consumption by 40%.  • Turn off the engine if you’re waiting for more than a couple of minutes. • At speeds less than 40 mph, roll down windows; more than 40 mph, use AC.  • Use the cruise control for more than 10,000 miles a year and save yourself 60  gallons of fuel. • Clogged air filters can cut mileage by 10%. • Tightening your fuel cap can prevent leakage of up to 30 gallons of gas a year.  • Skills that enable the driver to drive defensively and to avoid a crash in spite of driving errors by others; and •   Skills for the basic rules about turning, passing, backing and parking the vehicle. • Good drivers try to see 10 to 15 seconds ahead on the roadway (about one city  block). By looking ahead, you might avoid last minute moves such as sudden  stops or quick lane changes. • About every 10 seconds check the mirrors to see if any vehicle is following too closely. • When changing lanes, backing, slowing down or driving down a long hill, it  is important to check for traffic from behind the car and in your blind spots. • While checking the mirrors, do not take your eyes off the road for more than  an instant. The vehicle in front of you could stop suddenly. • Always leave yourself an “out.” Communicating means letting others know what you plan to do early enough  to avoid a crash. Anytime you plan to slow down, stop, turn, change lanes or  pull away from the curb, you should signal your intention. Be in the habit of  signalling your movements even when you do not see others on the road. Before  you signal, you must first see that your movement can be made safely. Although mirrors are useful, you should remember they do not show the full  picture. Mirrors leave “blind” spots in your field of vision. “Blind” spots are  the areas near the left and right rear corners of the vehicle that you cannot see  using the mirrors from the driver’s perspective. Therefore, before you make any  lane changes or turns, quickly turn your head and look over your shoulder to  see what is in the blind spot. Additional blind spots can be created by glaring  lights, dirty windshields, vehicles parked too closely to an intersection, bushes  and/or buildings. In these cases, ease your vehicle forward until you can see  clearly. Avoid driving in other drivers’ blind spots where it is more difficult for  them to see you. What you see is important for defensive driving. Communicating  Scanning Defensive Driving Driving involves two important types of skills: