Fuel and tires — Indiana Permit Test

Fuel and tires on the Indiana permit test — 5 rules, each with the reason behind it and a question on it while it is fresh.

The rules

Fuel use rises steadily above 45 mph; cars use about 50 percent more fuel at 75 mph than at 55 mph.

Higher speed means more air to push aside, which costs fuel as well as safety.

Fuel consumption increases steadily above 45 miles per hour, with passenger cars and light trucks using approximately 50 percent more fuel traveling at 75 miles per hour than at 55 miles per hour.

Indiana Driver's Manual, p.42

Tires can lose about 1 psi of pressure a month, so check all of them, including the spare, once a month or before a long trip.

Low tires grip and brake worse, and they can overheat and fail on the highway.

Tires have been known to lose up to 1 pound per square inch (psi) every month, so check all tires, including your spare, once a month or before a long trip.

Indiana Driver's Manual, p.43

Compare your tire pressure to the number on the sticker inside the driver's door or in the owner's manual, not to the number on the tire's sidewall.

The sidewall shows the tire's maximum, not the right pressure for your vehicle.

Open your car door and on the inside jamb there should be a sticker with your vehicle’s recommended psi.

Indiana Driver's Manual, p.43

Check tire pressure when the tires are cold, before driving or at least three hours after driving.

Driving warms the air in the tires and makes the reading too high.

Check your tires “cold”– before you’ve driven or at least three hours after you’ve driven.

Indiana Driver's Manual, p.43

In the penny test, if part of Lincoln's head is covered by the tread, the tread is deep enough; below about 1/16 of an inch, grip is greatly reduced.

Shallow tread cannot push water away, so the tire rides on top of it and slides.

If any part of Lincoln’s head is covered by the tread, you’re driving with the legal and safe amount of tread.

Indiana Driver's Manual, p.43

On the test

Above what speed does fuel use climb steadily?

45 mph. Higher speed means more air to push aside, which costs fuel as well as safety. Indiana Driver's Manual, p.42: “Fuel consumption increases steadily above 45 miles per hour, with passenger cars and light trucks using approximately 50 percent more fuel traveling at 75 miles per hour than at 55 miles per hour.”

How this works

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Learning one rule at a time, and proving it immediately, is what turns a manual you skimmed into something you actually know — and it makes studying feel like getting somewhere rather than like waiting to find out.

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Where these come from

Every rule here is checked against Indiana Driver's Manual, published by the Indiana Bureau of Motor Vehicles, and against the state code itself. Last checked 2026-10-03.