Car Maintenance Records: What to Keep and Why

Why the records matter

The plainest reason comes from the Federal Trade Commission. In its guide to auto warranties it says the warranty company could ask for your maintenance records, and it names the kind of work to keep records of: oil changes, tire rotations, belt replacement, new brake pads and inspections. The records help if you have to use the warranty, because they show you maintained the car. Without them, the FTC says, your claim might be denied.

The same page answers a question many owners worry about. You do not have to use the dealer for repairs or maintenance to keep your warranty in effect, and it is illegal for a dealer to deny warranty coverage because you had routine maintenance or repairs done by someone else. There is one exception: if the warranty says the work or the parts will be free, the dealer or manufacturer can make you use the facilities or parts it chooses. Aftermarket and recycled parts do not end the warranty either. If a defective part, or one installed badly, damages a covered part, coverage for that damaged part can be denied, but only after the manufacturer or dealer proves the part caused the damage. In every one of these cases, the record of who did what and when is your side of the story.

Service contracts, often sold as extended warranties, raise the stakes. The FTC notes that a contract might require you to follow all of the manufacturer's recommendations for routine maintenance and that skipping them might void it, and it says to keep your service records and receipts to show you have maintained your vehicle.

Records also help in less formal ways. A buyer trusts a car with a history more than one without. And a log lets you see patterns: the same warning light twice in a year, tires wearing out sooner than the last set, fuel use creeping up. The free car maintenance log gives you a service log and a fuel log as an Excel spreadsheet or a PDF to print, so the habit costs a minute per visit.

What to keep for each service

One row per visit is enough, even when several jobs were done at once. Fill it in the day the car comes back, with the invoice in your hand.

Record	What to note and why
Date	The day the work was finished. Warranty and service contract questions are about time as well as mileage.
Odometer reading	From the repair order, which per the FTC should show the reading when the car came in and when the order was completed.
Work done	Each job in plain words, one row per visit, including jobs you do yourself.
Parts	Names, sizes or numbers you may need again, and whether a part was new, remanufactured or salvage.
Shop or who did it	The shop name, or your own name for home jobs, so a later question has someone to ask.
Cost	The total paid, parts and labor; the repair order should break both down.
Receipt	Where the paper or scan is, numbered to match the row, plus any written warranty on the repair.

Log the jobs you do yourself as well, with the receipt for the parts and fluids. A row saying you changed the oil on a given date at a given reading, next to the receipt for the oil, is a record; a memory of doing it is not. Note recall repairs too. NHTSA's recall search by VIN shows unrepaired recalls, and it says the search will not show a safety recall that has already been repaired, so the paperwork from the shop is what shows the work was done.

Reading a repair order

The FTC's auto repair guide describes two documents. Before work starts, ask for a written estimate. It should identify the condition to be repaired, the parts needed and the anticipated labor charge, and it should state that the shop will contact you for approval before doing work beyond a specified amount of time or money. Get a signed copy.

After the work, get a completed repair order. Per the FTC it should list:

each repair that was done;
the parts supplied and the cost of each part;
the labor charges;
the odometer reading when you brought the car in and when the repair order was completed.

Check the order before you leave the counter, and ask for anything missing while the person who wrote it is still there. The FTC also suggests asking for all replaced parts, and notes that state law may require the shop to return them. It sorts parts into new, remanufactured (also called rebuilt or reconditioned) and salvage, so write the type in the Parts column. There is no standard warranty on repairs, the FTC says, so if a shop gives one, get it in writing and keep it with the receipt. If you end up in a dispute over a bill, the quality of the work or a warranty, the FTC's advice is to document every transaction with dates, times, expenses and the names of the people you dealt with, which is exactly what a log already holds.

Follow the owner's manual, not a generic schedule

This guide gives no service intervals, on purpose. The FTC's advice is to follow the manufacturer's maintenance schedule in your owner's manual for your type of driving. It adds that some repair shops use their own schedules with more frequent servicing than the manufacturer recommends, and suggests comparing the two and asking the shop to explain any service beyond the manual. A log makes that comparison easy, because you can see what was done and when.

The manual is also where several other numbers live. fueleconomy.gov notes that the proper tire pressure is usually on a sticker in the driver's side door jamb or the glove box and in the owner's manual, not the maximum printed on the tire's sidewall, and it recommends the manufacturer's recommended grade of motor oil. Write the oil grade and the tire size into the log once, so they are at hand at the next visit. When the check engine light comes on, fueleconomy.gov's advice is to have the car inspected by a mechanic; log the date and what was found, even if the fix was small.

Tracking fuel use: MPG and L/100 km

A fuel log measures what your car really uses, not what the window sticker promised. fueleconomy.gov describes the odometer method in four steps: fill the tank completely and note the odometer; at the next fill-up, fill it completely again and note the gallons and the new reading; subtract the old reading from the new one; divide the miles by the gallons. Its own example:

MPG, the fueleconomy.gov example

33,001.3 − 32,645.1 = 356.2 miles; 356.2 ÷ 13.5 gallons = 26.4 MPG

The same readings work in metric. Liters per 100 km turns the division around: liters divided by kilometers, times 100. With a fill-up of 41.8 liters after 612 km (48,822 minus 48,210), that is 6.8 L/100 km. Lower is better in L/100 km and higher is better in MPG, which trips people up when they compare figures from different countries.

One tank says little: a week of short trips or a long highway run moves the number a lot. Look at several tanks in a row. If the figure drops and stays down while your driving has not changed, mention it at the next service and note the date in the log. If you only topped up part of the tank, write that down and leave that row out of the average, since the method relies on full tanks at both ends.

Paper, digital, and the day you sell

One folder, in date order. Number each receipt and write the number in the log, so any row leads straight to its paper.
A scan or photo of every receipt. Some receipts are printed on thermal paper, which fades; a scan saved next to the spreadsheet keeps the record readable.
The VIN on the first page. NHTSA says the 17-character VIN is on the lower left of the windshield and on the registration card. It ties the records to this car.
Warranty and contract papers in the same place, with the repair warranties you got in writing.

When you sell, the records do their last job. NHTSA's advice to used car buyers is to compare the mileage on the odometer with the mileage in the car's maintenance or inspection records, so a complete set answers the first question a careful buyer asks. Federal law, as NHTSA describes it, also requires the seller to give a written disclosure of the odometer mileage on the title when ownership is transferred, with exemptions for vehicles 20 years old or older or of model year 2010 or older; the log helps you get that figure right. Hand over copies of the log and receipts, keep your own set, and black out your address, card numbers and insurance details before anything leaves your hands.

The free log and the tools

The car maintenance log has the columns from the table above, a fuel log, and space for the vehicle details including the VIN. The spreadsheet adds up service and fuel costs and works out fuel economy from your odometer readings in MPG, L/100 km, km per gallon or UK MPG; the PDF prints the same pages for the glove box.

Four tools fill the gaps. The MPG calculator works out gas mileage from miles and gallons or from two odometer readings, converts it to liters per 100 km and shows the cost per mile. The fuel economy converter turns US or UK MPG into L/100 km or km per liter and back, with the formula. Before a long drive, the trip fuel cost calculator estimates how much fuel a trip needs, what it costs and each passenger's share. When it is time for new tires, the tire size calculator decodes the size from your log and compares two sizes, including the effect on the speedometer. And if your fuel log has you wondering about the next car, EV vs gas car: cost per mile compared puts the running costs side by side.

Frequently asked questions

Do I have to service my car at the dealer to keep the warranty?

No. The FTC says you do not have to use the dealer for repairs or maintenance to keep your warranty in effect, and that it is illegal for a dealer to deny warranty coverage because you had routine maintenance or repairs done by someone else. The exception: if the warranty says work or parts will be free, the dealer or manufacturer can make you use the repair facilities or parts it chooses. Either way, keep the records, because the warranty company could ask for them.

Do aftermarket parts void my car warranty?

According to the FTC, your warranty stays in effect if you use aftermarket or recycled parts. If a defective part, or one installed incorrectly, damages a part the warranty covers, the manufacturer or dealer can deny coverage for that damaged part, but it must prove the aftermarket or recycled part caused the damage first. Write the part type in your log and keep the invoice.

How long should I keep car maintenance records?

The FTC pages used for this guide do not set a period. Their point is that records help if you need to use a warranty or a service contract, and that holds for as long as either is in force. In practice, keep the log and receipts for as long as you own the car and pass copies to the next owner.

What should a car repair invoice show?

The FTC says a completed repair order should list each repair, the parts supplied, the cost of each part, labor charges, and the odometer reading when you brought the car in and when the order was completed. Before work starts, ask for a signed written estimate naming the condition to be repaired, the parts needed and the expected labor charge.

How do I calculate my car's MPG?

Fill the tank completely and note the odometer. At the next fill-up, fill it completely again and note the gallons and the new reading. Subtract the old reading from the new one and divide the miles by the gallons. In the fueleconomy.gov example, 356.2 miles on 13.5 gallons is 26.4 MPG. For liters per 100 km, divide liters by kilometers and multiply by 100.

Should I give my service records to the buyer when I sell?

It helps the buyer and costs you nothing. NHTSA tells used car buyers to compare the odometer with the mileage in a car's maintenance or inspection records, so a complete set answers that check. Hand over copies, keep your own, and black out personal details such as your address or card numbers first.

Sources

Written by Tobias. Updated October 21, 2026.