How much fuel is wasted for every 10 p.s.i. of tire underinflation?
BC Class 1–4 overview
BC Class 1–4: Fuel-efficient driving
Starting and warming up a diesel, smart shifting and speed, idling, tire pressure, en route checks and vehicle choices that save fuel.
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- Topic drill
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Study reference: Driving Commercial Vehicles (ICBC, 2024 edition), Ch. 4 Fuel-efficient driving — Smart driving practices, Reduce idling, Choosing a fuel-efficient vehicle
All 10 questions in this test
Every question and its answer choices. The correct answers and explanations appear when you take the test above.
How much fuel is wasted for every 10 p.s.i. of tire underinflation?
- Almost none
- About five per cent
- About ten per cent
- About one per cent
Between 90 and 100 km/h, about how much of the fuel goes to overcoming air resistance?
- About one-tenth
- About half
- Almost all
- About one-quarter
How should you start a heavy diesel engine?
- With the throttle held halfway
- With zero throttle
- Pumping the throttle twice
- With ether every time
By how much can fuel-efficient driving techniques improve fuel economy?
- Up to 5 per cent
- Up to 30 per cent
- Up to 60 per cent
- They make no real difference
Driving at 105 km/h instead of 90 km/h uses about how much more fuel?
- The same amount
- About 20 per cent more
- About 50 per cent more
- About 5 per cent more
Which tire tread is more fuel-efficient on drive and steer axles?
- Mud-and-snow tread
- Rib tread
- Lug tread
- Mixed tread on each axle
How much can trailer side skirts and other aerodynamic features improve fuel economy?
- 15 to 20 per cent
- 1 to 2 per cent
- They only improve looks
- 40 to 50 per cent
How often does the guide recommend en route inspections, including tires and cargo?
- Every 30 minutes
- Once a day at the start
- At least every three hours
- Only at weigh scales
About how much fuel can a heavy truck burn per hour of idling?
- None with a modern engine
- Up to 15 litres
- Up to half a litre
- Up to four litres
How long should you warm up a heavy diesel engine in temperatures above 0 °C?
- Until the cab is warm
- Under one minute
- 15 to 20 minutes
- Three to five minutes
Fuel-efficient driving: key rules to remember
Our summary of what the official handbook says on this topic, in our own words. Read it before or after the practice questions above, then check the original chapter. Read the official chapter ↗
Making smart choices, fuel and route planning (p. 69–70)
- Nearly 30 per cent of Canada's greenhouse gas emissions come from vehicles.
- Fuel-efficient driving techniques can improve fuel economy by up to 30 per cent.
- Summer fuel can improve economy by up to three per cent but can cause engine problems in cold weather.
- Biodiesel gives power similar to diesel with less carbon dioxide, sulfur and particulate emissions.
- The most fuel-efficient route usually avoids heavy commuter traffic, busy city streets and hills.
- A flat multi-lane highway saves four to 11 per cent over a flat two-lane highway, up to 18 per cent over a mountain highway and 25 to 35 per cent over suburban roads.
- Snow-covered roads can raise fuel use by 15 to 20 per cent.
Starting the engine (p. 70)
- Start a heavy diesel with zero throttle; do not pump the throttle.
- Warm up three to five minutes, or seven to 10 minutes below 0 °C; longer wastes fuel and can damage the engine.
- Check that oil and air pressure reach their normal ranges.
- Use ether sparingly and only if the owner's manual allows it; it can damage the engine.
Smart driving techniques (p. 71–72)
- Accelerate slowly and keep r.p.m. down for the first several kilometres after warm-up.
- Shift progressively, before maximum governed r.p.m.; run in the highest gear range at low r.p.m.
- Proper shifting can improve operating costs by 30 per cent; always use the clutch to protect gear teeth.
- Back off the throttle at the top of a hill and select a lower gear for the descent.
- Cruise control in appropriate places can reduce fuel use; turn the retarder off when not needed.
- Driving 105 km/h instead of 90 km/h is 15 per cent faster but burns about 20 per cent more fuel.
- See-think-do keeps a steady speed and saves momentum: power not used is fuel not burned.
- Coasting toward a stale red light so you do not fully stop saves fuel.
Reduce idling and maintain your vehicle (p. 72–73)
- Turning the engine off at truck stops or depots is cheaper than idling; auxiliary power units can run air conditioning or refrigeration.
- Idling can burn up to four litres of fuel per hour; cutting one hour a day saves over 1,000 litres a year.
- Every 10 p.s.i. (69 kPa) of underinflation wastes one per cent of fuel.
- A pre-trip inspection before driving is the law.
- Do en route inspections, including tires and cargo, at least every three hours.
- Air leaks make the compressor run longer and waste fuel, and weaken the air brakes.
- Low-viscosity lubricants such as synthetic oil can improve economy by up to four per cent.
Choosing a fuel-efficient vehicle (p. 74–75)
- Between 90 and 100 km/h about half the fuel is used to overcome air resistance.
- Trailer side skirts and rear air dams and other aero features can improve economy by 15 to 20 per cent.
- On a flat deck, keep the load low and tarp it to cut drag.
- Rib tread tires are more fuel-efficient than lug tread on drive and steer axles.
- Super-single tires on drive axles have low rolling resistance, weigh less and lower vehicle height.
- Fuel heaters prevent fuel gelling in cold weather; block and oil pan heaters help cold starts.
- Misaligned wheels that do not track parallel to the direction of travel increase aerodynamic drag.
- For the same payload, the lighter truck gives better fuel economy.
Other topics
- Licence classes, endorsements and testingClass 1 to 4 and what each covers, minimum ages, the air brake (code 15) and heavy trailer (code 20) endorsements, the driving record and medical rules, learner supervision, MELT and retest waiting periods.
- Heavy vehicle brakingHow brakes turn motion into heat, stopping time and following distance, speed and weight effects, brake fade, retarders, downgrades, water, runaway lanes and ABS.
- Basic commercial driving skillsFollowing distance, danger zones, off track and turns, curves, roundabouts, backing, mirrors, emergency vehicles, double-clutching, railway crossings and night driving.
- Tires, warnings and personal safetyTire pressure and tread limits, wheel checks, required braking systems, flashing lights, warning devices for disabled vehicles, carbon monoxide, seatbelts, phones, impoundment and fire fighting.
- Backing and handling trailersBacking a semi-trailer, rollovers and load height, double trailers, trailer whipping, parking a trailer and weight distribution on a tractor-trailer.
- Coupling and uncouplingCoupling and uncoupling a fifth wheel step by step, the tug test, landing gear, pintle hitches, safety chains and drawbars.
- Loading and weight distributionWhere to place heavy loads on a truck, axle load shares for freight, dump and mixer trucks, covered aggregate loads, livestock and liquid tank loads.
- Cargo securementThe North American cargo securement standard, tiedown condition, how many tiedowns and how strong, binders, front-end structures, load projections and vehicles carried as cargo.
- Dimensions, weights and permitsHeight and width limits, mirrors, GVW and licensed GVW, overload and oversize permits, pilot cars and reporting to weigh scales.
- Dangerous goods and signs for commercial driversDangerous goods training and documents, reporting spills, placard classes, CANUTEC, runaway lanes, low clearance, transit priority and zone signs.
- Operating a busBus passenger safety, leaving the curb, transit right-of-way, highway stops, fares, standing passengers, required equipment, baggage and the bus pre-trip.
- School busesWhich licences cover school buses, daily brake checks, school bus equipment and signs, loading and unloading, flashing red lights and railway crossings.
- Taxis, limousines and ride-hailingClass 4 restricted, taxi and limousine definitions, passenger transportation licences, seating, duty to carry and when you may refuse, jump seats and passengers with disabilities.
- Ambulances and special vehiclesLicences for ambulances and special vehicles, when emergency vehicles may use lights and sirens, yielding to them, and equipment rules that depend on seating capacity.
- Hours of serviceOn-duty and off-duty time, daily and shift limits, cycles and resets, deferral, sleeper berths, personal use, ELDs and records of duty status, the 160 km exemption and other jurisdictions.
- Air brake componentsWhy air brakes, brake chambers and slack adjusters, s-cam brakes, compressor, governor, reservoirs, foot valve, air dryers and ABS.
- Dual air brake systemsThe dual foot valve, primary and secondary circuits, one-way check valves, the low-air warning, quick release and relay valves, and what happens when one circuit fails.
- Spring parking brakesWhy parking needs mechanical force, how spring brakes apply and release, compounding, caging, blended air and safety actuators.
- Tractor-trailer air systemsSupply and control lines, glad hands, trailer emergency application, the tractor protection system, the trailer hand valve and bobtail tractors.
- Air brake adjustmentPushrod stroke limits, checking manual slack adjusters by the applied and pry methods, adjusting them, automatic slack adjusters and common misconceptions.
- Trip inspections and reportsWhen inspections are required, which vehicles need written reports, cargo securement re-checks, report rules, pre-trip procedure, brake checks before hills and en route checks.
- Class 1 pre-trip inspectionThe Class 1 road test pre-trip: timing, slack adjuster set-up, fifth wheel and landing gear checks, leakage limits with trailers, tug tests and breakaway checks.
- Air brake pre-trip testThe air brake pre-trip on the road test: draining reservoirs, governor cut-out and cut-in, low-air warning, trailer supply valve closing, build-up time and leakage limits.