How often should I change my engine oil? This question / discussion has come up many times over the 30+ years I have been involved with automotive and other vehicle maintenance and repair. I have found it hard to convey all of the information and / or knowledge I have on this subject in a few sentences, so I intend to explain much of what I know about the subject fully here, and hopefully refer people to this information in the future, so they can make a well informed decision on this matter on their own, for their particular situation. All of this information applies to any vehicle with a gasoline powered four stroke internal combustion engine, which covers most cars and light trucks on the road today. All of my experience applies to the weather, driving conditions, and supplies in the upper midwestern U.S., and may not be similar in different climates and whatnot.
If you wish to cut to the chase, changing engine oil every 3,000 miles is a reasonable rule of thumb for most people and for most modern passenger vehicles and light trucks. That being said, changing oil after 500 miles is not always wasteful, and going 6,000 or 8,000 miles between changes is not necessarily destroying your engine, or shortening its life. Hogwash! you may say, how can this be? And who is this ‘Zane’ guy to claim expertise in this matter? Please continue reading and I will attempt to fully explain.
My Dad has owned and operated an auto repair shop for almost 50 years, so I have been around this business my whole life. I have also owned and operated an auto repair shop for over 15 years where we work on or check over 2,000+ vehicles per year. In addition, for several years our business shared space and worked closely with an independently owned automotive lube center which regularly performed 30+ engine oil changes every day.
Okay, back to you. If you are the type of person who prefers not to lift the hood of your vehicle, for whatever reason, it is in your best interest to get your oil changed every 3,000 miles at most. There are several reasons for this advice, which I will try to explain. Most vehicles can go 2,000 miles or so, and still have the oil level read right at the full mark on the dipstick. However, around this distance, many vehicles will start using a bit of oil, which tends to accelerate the more miles driven before the oil is changed. So if you get to 3,000 miles, and are 1/4, or ½ quart low on oil, no problem, fresh oil and filter, back to full, and you are on your way. I have told many people, if your engine uses or loses (via seeps or drips) less than a quart every 3,000 miles, no worries, keep driving it, this is not a problem which you need to spend money on yet. Most vehicles will go another 100,000 miles or more in this fashion. The trouble arises for the ‘not open the hood’ types when they go 5,000 or 6,000+ miles before getting the oil changed, at which point they are 2 – 3+ quarts low on oil. Many cars only have a 4 to 5 quart oil capacity, so at this point the engine is dangerously low on oil. This situation tends to be more prevalent on cars with higher miles, however is not uncommon for vehicles with 20 or 50 thousand miles. The 3,000 mile mark tends to be around 1 ½ – 2 months worth of driving for most people, which is also a reasonable amount of time between a general check of fluid levels, tire pressure, etc. Noticing a small coolant leak at this time, for example, and addressing it may prevent you from having the car overheat at midnight 37 miles from home when you have to work in the morning. ‘Do-it- yourself’ type people, who are able to check stuff over every 1,000 miles or so and keep the oil level within a quart of the full mark should have no oil related problems changing oil and filter every 5 to 7,000 miles with a decent synthetic blend oil, which is the most common oil on the market these days.
Back in the 1970s and 80s, 2,000 miles was the standard for engine oil changes. Engine rebuilds were much more frequent in those days, as well as major engine repair work. On average, engines probably lasted about 1/2 to 2/3rds as many miles as they average nowadays. As an anecdotal example, in the early 1980s, my Dad hardly went a month without replacing at least one camshaft in a Chevy V8. Now, in 2013, I can’t recall the last time I heard of any V8 engine needing a new cam. There are dozens of reasons for this reduction in the necessity of major engine repairs. Chief among them are improved quality of engine oil, and advances in engine design, manufacture, and metallurgy.
If you operate your vehicle anywhere that experiences winter, there are a some more concerns which contribute to the 3,000 mile recommendation. Most competent mechanics set the tire pressure on any vehicle when changing the oil. Tire pressures change dramatically with large outdoor temperature changes. Hot air expands, cold air contracts. If your tire pressures are set properly in September when it is 80 degrees outside, by January with a -10 degree temp, your tires will be dangerously under inflated. Also, on a very cold winter day, many vehicles exhibit a light brown, foamy substance on the inside of the oil cap, and/or inside the valve cover. This is due to moisture inside the engine. In very cold temperatures, engines often do not get warm enough for moisture to evaporate and exit the engine as steam via the PCV (positive crankcase ventilation) valve. Water inside an engine oil system is a bad thing. The brand, type, weight, or cost of the oil being used cannot prevent this issue. Changing the engine oil, waiting for the weather to change, or running the engine at high rpm for an extended period are about the only things which can resolve this issue. Changing the oil is probably the best of these 3 options.
True story # 1:
One evening about 5 years ago, a person came in to the office and asked for an oil change. Customer mentioned it was the first oil change on a brand new Volkswagen. When Jim pulled the car in, he noted it had 22,000 miles on it. Removed the oil drain plug – and nothing came out. All of the engine oil had turned to sludge, baked to the inside of the engine, or been burned and went out the exhaust. Jim asked the customer why they went so long before changing oil, customer felt that a new car shouldn’t need to be worked on right away…