I've made several spreadsheets over the years for various needs, and vehicle service records is one. Pretty easy to do, and can be as detailed or vague as you want.
Mine I do the following:
Besides just the following information on its own sheet, I create another sheet that gives the vehicle's VIN, build sheet (Jeeps are easy to get build sheets for), date the vehicle was purchased, mileage at purchase, purchase price, tire size, general vehicle features
Date, mileage, description of service, shop, or who performed the service, and the cost of the service
On another sheet I list the common air filter part numbers, oil filter part numbers, quarts of oil required, transmission fluid requirements, spark plug part numbers, etc.
So for me within 1 excel document I typically have 3-4 and sometimes more sheets. I have a 1988 Ford Bronco 2 which has the above sheets plus a sheet for keeping track of things I want to look for at pick a part yards, mods I want to do, things I need to fix, etc.
On my lawn & garden equipment I made a little service tag which gives the date, service performed, hours, etc. on it, the tags are laminated and a hole punched in them, and I use a little piece of string and attach it to a handlebar or other location out of the way but easy to see to keep track of services on them...I just write on the tag with a sharpie and when I service it next time I just rip the tag off and fill out a new one, kind of like that sticker on your windshield for oil changes. Another thing you can do is like on my lawn tractor I also write the date and hours of the last oil change on the oil filter as its extremely easy to see, just use a silver sharpie if the oil filter is black.
So many things you can put in the spreadsheet, and of course you can add more sheets to an excel and many other spreadsheet type applications so you have 1 file with multiple sheets for each vehicle, or heck throw them all in one file with the tabs at the bottom for each sheet labeled for each vehicle or piece of equipment.
I keep a folder/binder of all stuff done to each of my vehicles, as well as an electronic folder on my computer with copies of everything as well, so I can easily access records regardless. Its amazing the number of people that get excited when you sell them a vehicle and you hand them a binder or folder full of every repair or maintenance done to the vehicle...and in the case of one vehicle I sold, the buyer bought my truck over another with a couple thousand less miles because I had every single document for the vehicle from the day it was bought till the day it was sold, every single service and repair was documented with receipts even tire replacements, camper shell install, fuel log, it was all in a binder for the buyer and ultimately got me the full asking price for a vehicle that had a couple thousand more miles and a couple thousand dollars more than another of the same vehicle with less miles and cheaper price, all because I had all the documentation on the vehicle's service and repair history.
