MECHANIC GUIDES

What Is the 8% Rule for Cars? It Leaves Out the Repair Bill

By Anthony LimpertASE Master Automobile Technician

2026-10-15 · 8 min read

The 8% rule for cars says your total car payments should be no more than 8% of your gross income, the pay you earn before taxes. It is the last part of the 20/3/8 rule from The Money Guy Show. Put 20% down, pay the loan off in 3 years, and keep every car payment in the house under 8% of what you make.

Here is what the rule does not count. Oil changes, brakes, tires, batteries and the alternator that quits on a Tuesday. We run a repair shop in San Jacinto and Hemet, California, and we list 29,369 shops and mechanics on MechanicRank, so we see the repair side of car budgets every day. This guide shows how the 8% rule works, then adds the part the money shows skip. What it costs to keep the car on the road.

The Short Version

• The 8% rule caps your car payments at 8% of gross income. On $60,000 a year, that is $400 a month for every car you finance, not $400 per car.
• It covers the loan payment only. Insurance, gas and repairs sit on top of it.
• AAA puts maintenance, repair and tires on a new car at 11.04 cents a mile. At 15,000 miles a year that is about $138 a month.
• Add insurance and gas and a $400 payment turns into about $840 a month to own the car.
• One mid size repair, like an alternator or a water pump, can cost one to two months of that $400 payment.

Where the 8% Rule Comes From

The 8% rule is not a law or a bank rule. It is a rule of thumb from The Money Guy Show, a personal finance show. Their 20/3/8 guide, last updated July 29, 2026, lays it out in three parts.

• 20 percent down. Put at least 20% of the price down so you do not owe more than the car is worth.
• 3 year loan. Finance for no more than three years. If a deal has a longer term, the guide says to pay it off in three anyway.
• 8 percent of gross income. Keep your total car payments at or under 8% of your income before taxes. The guide is clear that the cap is for all your vehicles together, not each one.

The guide also says luxury cars should not use the rule at all. It says to buy those with cash or finance them for a year or less. And it only lets an electric car in if its upkeep and loss in value look like a normal car's. Those two lines are the only places the guide really touches what it costs to keep a car running.

This is general information, not financial advice. Your own budget, debts and goals matter more than any rule of thumb.

How the 8% Rule Compares to Other Car Rules

There are a few car budget rules out there, and they do not count the same things. This is the part most pages blur. Only one of them puts upkeep inside the cap.

So the 8% rule is the strictest on the loan and the loosest on everything else. That is not a flaw. A short loan with a small payment leaves room in the budget. But the room only helps if you use it for the car costs the rule leaves out.

What 8% Looks Like on Real Paychecks

Take your yearly pay before taxes, divide by 12, and multiply by 0.08. That is your cap for all car payments together. Here are three worked examples.

What the 8% Rule Leaves Out

AAA has priced car ownership every year since 1950. Its Your Driving Costs 2025 fact sheet puts the average cost to own and run a new car at $11,577 a year. Here is how its numbers stack on top of a $400 payment. The worked example uses 15,000 miles a year.

Add it up and the $400 car costs about $842 a month to own and drive. That is close to 17% of a $5,000 gross month, more than double the 8% on the sticker.

The maintenance line moves with your miles. At 10,000 miles a year AAA's rate works out to about $92 a month. At 20,000 miles it is about $184 a month.

One more thing about that AAA number. It is the average for a new car over its first five years and 75,000 miles. It even counts the cost of an extended warranty. An older car with 120,000 miles on it will not stay that cheap. That is when the big parts start to go.

What One Repair Costs Against a $400 Payment

AAA gives you an average. Repairs do not come as an average. They come as one bill on one bad day. Here is what common repairs cost from our own repair cost guides, next to the $400 payment from the $60,000 example. Our ranges use real parts prices, standard labor times and labor at $95 to $140 an hour. Your car, your city and the parts brand move the price.

Read the middle of that table. A water pump or a timing belt is one to three months of car payments, due all at once, with no loan to spread it out. That is the bill the 8% rule does not plan for. It is also the bill that puts people on a credit card.

How to Make the 8% Rule Fit Real Repair Costs

You do not need a new rule. You need the 8% rule plus a plan for the car itself. Here is what we would tell a friend who asked us at the counter.

• Set aside a repair amount every month. AAA's 11.04 cents a mile is a fair starting point. Multiply your yearly miles by 0.11 and divide by 12. On 12,000 miles a year that is about $110 a month.
• Keep paying the car after the loan ends. The 3 year loan is the best part of the rule. When it is paid off, keep moving that payment, or part of it, into a car fund. Years four and up are when the repairs in the table above show up.
• Budget more for an older car. AAA's number is for new cars. If yours is past its warranty or over 100,000 miles, plan above it.
• Get a used car inspected before you buy. A pre purchase inspection finds the worn struts, the leaking water pump and the slipping transmission before they are your bill.
• Do the maintenance on time. An oil change at $65 to $160 is cheap next to a $960 to $2,460 head gasket. Skipped coolant and oil service is how small bills become big ones.
• Get a written estimate before any work. The FTC's auto repair guide tells drivers to get one, and to ask the shop to call before it goes over that amount.

Should You Use the 8% Rule?

As a cap on the loan, it is a good one. A small payment on a short loan keeps you from owing more than the car is worth, and it frees money every month.

Just do not stop at 8%. The payment is the part you know. The repair bill is the part you do not, and it is the part that breaks budgets. If the 8% payment plus about $100 to $185 a month for upkeep still fits, you are in good shape. If it only fits with nothing left for repairs, the car is too much car, even if it passes the rule.

What We Charge at Our Own Shop

We post our prices. Here are ours at Supercanic, the shop in San Jacinto and Hemet, California, that runs MechanicRank.

• Labor is $150 an hour.
• Nights from 10pm to 6am are $300 an hour.
• Labor carries a 90 day or 5,000 mile warranty. Parts carry the maker's warranty, 1 to 3 years.

Find a Mechanic Near You

MechanicRank lists 29,369 repair shops and mechanics in 6,182 cities. Every listing shows the shop's phone, reviews and hours, and the phone rings the shop direct.

Search your ZIP code to compare shops near you, or check what a mobile mechanic costs if you would rather have the work done in your driveway.

Sources

We opened each of these on October 10, 2026.

• The Money Guy Show, the 20/3/8 car buying rule guide
• The Money Guy Show, car affordability calculator
• AAA, Your Driving Costs 2025 fact sheet (PDF)
• Quicken, how to use the 20/4/10 rule for buying a car
• Ramsey Solutions, how much car can I afford
• Federal Trade Commission, auto repair basics
• MechanicRank repair cost guides, our own ranges from parts prices, standard labor times and $95 to $140 an hour labor

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