Oil change: miles or time?
February 11, 2014 9:56 AM   Subscribe

Oil changes: miles or time? I drive a little 2011 Mazda M2. My commute to work is about 14 miles round trip. I don't drive it much else. My last oil change was January 2013 and 5231 miles. The sticker says next change is May 2013 or 10231 miles. Needless to say it's well beyond May 2013 but I'm still only at 9200 miles. Should I get an oil change or wait for the mileage?

I do routine stuff like checking my various fluid levels, making sure my tire pressure is good, that sort of thing. But what's more the driving force with oil change recommendations: time or mileage?
posted by xmutex to Travel & Transportation (24 answers total) 7 users marked this as a favorite
Our Toyota, Chevy and Honda cars have all said change the oil every 5000-7000 km (different cars) or every 6 months. So I would think you are well over due. We changed the oil Jan/Aug on our low mileage cars.
posted by saradarlin at 10:02 AM on February 11, 2014

It's past time for you to do it, but the 3 month "wisdom" is outdated.
posted by cecic at 10:07 AM on February 11, 2014

Oil degrades through use and over time. You want to change at whichever benchmark point comes first. You're 6 months overdue for a change.

Regular oil changes can make a huge difference in how long your engine lasts, the $20 you saved by not getting the oil changed at 6 months isn't worth the extra wear on the engine.
posted by HuronBob at 10:07 AM on February 11, 2014

Miles or time...which ever comes first. Your time has come!
posted by artdrectr at 10:08 AM on February 11, 2014 [3 favorites]

If you're in California (and so not seeing much humidity/extreme weather) as your profile suggests I'd be tempted to go for the time rather than mileage:

1: Cold starts are the worst for a car, so your low mileage is one of the reasons time limits are suggested. You will have had more cold starts within that period that someone who racks up twice as much mileage as they'd be sat on the freeway with a nice warm engine for most of it (the least wearing of engine modes). So in your case in particular, time is very much the issue with a greater percentage of 'high wear' driving miles.

2: Assuming you have synthetic oil (don't penny pinch on oil AND stretch oil change intervals) then 12 months is probably as long as I'd ever leave it given the choice, probably 9 months if I were to balance what's best with 'what I can be bothered to pay for'.

3: 4 months in a mild climate like San Diego is a bit soon for my tastes. In the wintery parts of the world then I'd suggest changing it sooner, but not somewhere as mild as SoCal. 6 months to 9 months (depending on usage and money) would be my bet. I'd prefer to stick to 6 months, personally, or mileage, whichever is sooner.

4: If money is an issue, it's better to change cheaper oil more often than expensive oil less often (if that makes sense). If you can only afford an oil change every 9 months, make it synthetic. Only use non-synthetic if you can afford to change it on the schedule.

%: If money is no object, stick to the schedule. It's much, much safer. Engines do not die from having their oil changed too often, but they do from not having it changed often enough. Draw your own conclusions.

Oh, and change your oil...
posted by Brockles at 10:09 AM on February 11, 2014 [2 favorites]

Yeah...change it. Not only does oil degrade over time, it accumulates acidic contaminants that you don't want spending quality time in contact with the inside of your engine.
posted by kjs3 at 10:17 AM on February 11, 2014

The oil they would put in has likely been sitting in storage since before May 2013.
posted by The 10th Regiment of Foot at 10:18 AM on February 11, 2014

The oil they would put in has likely been sitting in storage since before May 2013.

That isn't relevant to anything. Being stored in an airtight plastic bottle is completely different to when it is sitting in a heat cycling, fossil fuel burning friction machine that spends its life pushing the oil through tiny pressurised galleries carrying tiny flakes of metal and carbon.
posted by Brockles at 10:22 AM on February 11, 2014 [5 favorites]

Never pay attention to stickers put in by a dealer or a quick lube place. Their goal is to get you in as often as possible.

Go by the suggestions in your manual. Mazda (like most Japanese manufacturers) has fairly straightforward recommendations listed for their cars. Given that your car is fairly recently built, the odds are that you can safely get somewhere in the neighborhood of 7,500 out of an oil change that uses decent oil, but the manual will tell you.

Your car may also have some kind of oil monitoring system installed. Hondas have this, and they work great.

As for time, the idea that oil "degrades over time" is overrated in my book, especially if we are talking synthetics. Still, go by what the manual tells you. If it only tells you miles, then consider changing your oil maybe once a year, or once every 8-10 months, if you're driving it that gently and it will make you feel better. I'm not sure there is any conventional wisdom about how long oil can sit in a car, whether conventional or synthetic.
posted by Old Man McKay at 10:23 AM on February 11, 2014 [1 favorite]

If the oil is sitting, it makes no difference what the vessel is. Of course if it isn't being cycled then it is settling and not passing regularly through a filter.
posted by The 10th Regiment of Foot at 10:33 AM on February 11, 2014

Response by poster: Ya'll making me feel guilty. Thanks for the feedback & info!
posted by xmutex at 10:34 AM on February 11, 2014 [1 favorite]

Whichever comes first.

We're talking about $25 and 30 minutes.
posted by Ruthless Bunny at 11:03 AM on February 11, 2014

Miles or time, whichever comes first. As others have said though, go by what's in the owner's manual not what your mechanic or lube shop puts on that little sticker that they stick on the inside of the windshield. That's a calculated ploy to get people to change their oil more often than necessary (there have even been lawsuits over it, because it's misleading) which is good for the shop but bad for the owner and the environment. (Used motor oil is a significant environmental problem for a number of reasons. Proper disposal reduces the problem, but doesn't solve it.)

Modern cars and modern oils last a lot longer than they did back in the day. It varies a great deal from car to car, but whatever is in your owner's manual is probably close enough to correct as makes no difference as long as you also use an approved motor oil (also as listed in your owner's manual). Car manufacturers do a tremendous amount of research into this sort of thing, and while their recommendations of course build in a reasonable safety margin they're definitely based on a lot more evidence than the recommendations that you'll get at a shop are.

Fortunately you probably haven't done any real damage to your car, because of the aforementioned margin of safety built into the manufacturer's maintenance schedule, but you should get your oil changed at the earliest opportunity. Or, heck, take this opportunity to do it yourself – it's easy enough, and you'll both learn something and save some money in the process! If you do, just watch a tutorial first and make sure to change your filter as well as your oil.
posted by Scientist at 11:04 AM on February 11, 2014

If the oil is sitting, it makes no difference what the vessel is.

Again, this is just not true. Clean, brand new oil in a sealed and airtight container will last indefinitely. Oil that has been worked, heated, contaminated repeatedly by being run in an engine for thousands of miles is a completely different situation and storage environment (and is essentially open to the atmosphere). Used engine oil is not the same as new engine oil and it will not last indefinitely even if it is just sitting, no matter how many times you filter it. Please don't post misinformation.
posted by Brockles at 11:07 AM on February 11, 2014 [4 favorites]

Do you want the manufacturer to honour your engine warranty? Then get the oil changed in accordance with the service intervals.

This. My husband used to have, coincidentally, a Mazda. He bought it new, but wasn't as diligent about changing the oil as he should have been, and didn't always save the receipts when he did. The engine seized, and because we couldn't prove that we had done the regular maintenance, it wasn't covered under warranty.

A few quick, cheap oil changes on a regular basis is way better than a $6000 engine.
posted by thejanna at 11:10 AM on February 11, 2014

Oil that has been worked, heated, contaminated repeatedly by being run in an engine for thousands of miles is a completely different situation and storage environment

Right, however this particular oil has not gone thousands of miles, it has gone dozens of weeks. You are also assuming that the poster is getting oil out of a bottle and not out of a drum, where it is less sealed than a crank case as would be the situation at a mechanic or dealership. Oil is broken down into shorter hydrocarbon chains by heat and mixture with fuel, if the engine is not running neither of these things are happening. Unless they are driving this car on a race course or without coolant for some reason there should be very little oxidative breakdown of the oil during that time. So yes, used oil is not the same as new, but it is not spoiling just because time has gone by.
posted by The 10th Regiment of Foot at 11:41 AM on February 11, 2014

I only use full-synthetic motor oil in my cars because I work from home and my wife works 4 miles away so don't put a lot of miles on either of our cars. As I understand it, once you put it in the engine, conventional oil doesn't last as long as a full-synthetic even just sitting there not being driven.

There are labs where you can pay $25 or so, send them a sample of your oil and they can give you some really specific expert advice on the condition of your oil and when you should change it.

Otherwise I would, and did, switch to a full-synthetic and change it twice a year and generally ignore the mileage. I also started changing it myself because it turns out to be REALLY easy if you have the right tools (a good jack, mostly) and the tools pay for themselves after a few changes.
posted by VTX at 11:53 AM on February 11, 2014

This oil has gone 4,000 miles and over 53 weeks. Used engine oil has contaminants in it that shouldn't be left to sit in an engine for over 12 months. It is not, in any way, the same situation as an engine sitting in storage with brand new oil in it versus that same brand new oil sitting on the shelf. That's the only time your suggestion that it doesn't matter if it sits in the engine or on the shelf would hold any water.

If the oil has been used, the time does matter. Specifically in this use case, the mileage over that time matters as the style of usage that his mileage/week produces is one of the harder cases on the engine (and hence the oil). So, particularly here, an extended use case of cold starts is problematic for the oil, as is contaminated engine oil sitting in an engine for an extremely extended period. The oil has had a hard life - more so than the mileage suggests and time is a factor.

it is not spoiling just because time has gone by.

I didn't say it was. Not 'just' because time has gone by. New oil won't spoil sitting in an engine, but oil will be spoilt by being run in the engine, and then is problematic when it is sitting. It is not - at all - the same as new oil sitting in an engine. Also, the oil breaking down through sitting isn't as much of an issue as what the stuff in the oil is doing to the metal/seals/components.

getting oil out of a bottle and not out of a drum, where it is less sealed than a crank case as would be the situation at a mechanic or dealership.

It's unlikely any drum at a dealership lasts more than a couple of weeks just through volume usage, so it certainly won't be stored open for extended periods. So either way your comment was misleading and incorrect, although possibly not for the initial reasons you assumed I was saying so. It doesn't matter how long brand new oil has been sitting (within reason) before it goes into your engine, it is till better than old oil sitting in it for the same prolonged period before you change it.
posted by Brockles at 12:02 PM on February 11, 2014 [2 favorites]

Brockles: "2: Assuming you have synthetic oil (don't penny pinch on oil AND stretch oil change intervals) then 12 months is probably as long as I'd ever leave it given the choice, probably 9 months if I were to balance what's best with 'what I can be bothered to pay for'."

People who are willing to put way more effort into testing these things and paying for oil analyses than I am find that in modern engines, plain 'ol pennzoil yellow bottle is about as good as any synthetic on a 10k mile/1 year change interval. That would be my personal limit, and then only if I knew I were otherwise treating it well and it the weather had been mild. One of the biggest contaminants that you will get in a car that isn't driven much is water from condensation. Over time, just sitting, you can get a surprising amount of water mixed in. Not good. Running the car regularly evaporates the water before enough gets in there to be a problem. If 14 miles is enough to get your engine up to temp and keep it there for at least 5 minutes, and you're doing that drive at least a couple of times a week, I'd say you'll be fine changing it once a year or at the mileage your manual indicates, whichever comes first.

That said, cars are rather expensive pieces of machinery, so if you plan to keep it until it dies, don't cheap out, the extra money you'll spend changing the oil at 6 month intervals will add basically nothing to your operating cost and will likely get you at least some extra engine life.
posted by wierdo at 12:25 PM on February 11, 2014

Time or miles, whichever comes first. 10,000 is pretty common these days, but check your owners manual.
Also check if it has a time recommendation. My gut tells me up to a year is okay, but I don't have anything to base that on.
posted by J. Wilson at 12:39 PM on February 11, 2014

At our shop, we don't put a time interval, and we tailor the mileage based on what we know of our customers' habits. The traveling salesman goes 8000 miles. The kid whose parents bring in the car, and who drives it like he stole it, goes 3000 miles.

Besides the issues with worn, dirty oil, bringing the car into your mechanic regularly can save a bundle because he or she will look the car over while it's draining, and advise you of any issues. Your tires are wearing funny. Your brakes are gonna need changing at the next oil change. Your brakes weren't squealing, but are wearing very unevenly. Your engine has a leak and there wasn't any oil on the dipstick. Etc.
posted by notsnot at 4:16 PM on February 11, 2014

The manual (PDF) says the oil should be changed every 6 months or 7500 miles, whichever comes first.
posted by zsazsa at 5:40 PM on February 11, 2014 [1 favorite]

When in doubt on changing or not changing -- especially when you have conflicting information from people who take very passionate opposing positions -- I'd recommend the following:

What does the owner's manual say? Do at least that.

If you don't change it as often as the owner's manual says, they can deny a warranty claim if something happens to the engine. Engine sludge is a very real problem in today's cars due to various factors, and even as maintenance intervals lengthen, the impact of waiting too long is becoming more expensive. Change it as often -- mileage or time, whichever comes first -- as the manual suggests, and that's the definitive answer you need for your question, at least until your warranty runs out.

Of course, you probably want to keep your car longer than the warranty, and the owner's manual only represents the longest/furthest you should go between changes. Is there any benefit to changing the oil more often/over less distance? I say sometimes yes, and here are those use cases:

#1: Change it more often if the manufacturer was paying for maintenance.

More manufacturers offer "free" maintenance these days, and a funny thing happens if you look at the maintenance specifications between a car built the year free maintenance wasn't offered and the next year's model that had free maintenance, but was otherwise identical: the oil change intervals got longer. It's reasonable to assume that non-free maintenance intervals are scheduled to minimize warranty claims, while free maintenance intervals are scheduled at a balance between minimizing warranty claims and minimizing the manufacturer's cost for your maintenance.

So if you're car's a long-term keeper, and the manufacturer paid for the maintenance, either change it as often as the manufacturer recommended for your model of car before they offered free maintenance (if that's a scenario that fits your model) or consider squeezing an extra change in between (if scheduled 10,000, do every 5,000) or rounding down to a convenient internal (if scheduled 7,500, do every 5,000.)

#2: Change it more often if a trusted specialist recommends it.

Drive an enthusiast car? Something swedish or german, perhaps? Long before it is out of warranty, go chat with the local specialist. He wants your long-term business, so he might encourage you to over-maintain your car, but if it's a keeper then over-maintenance is the route to take. Getting a few opinions from different specialists might make sense.

#3: You enjoy working on your car.

If you change your own oil, and are the type of person who likes maintenance tasks, a regular oil change -- even if a little early -- is a great excuse to get under the car and see what's going on. What better time to notice torn CV boots or minor fluid leaks?

#4: You drive a turbocharged car.

Anyway, that's my advice, and I happen to be taking it: I drive a 2013 VW GTI with a turbocharger and a "free" maintenance interval of 10,000, and I pay to have the oil changed at the 5,000 intervals between. I'll also be paying to have the valves cleaned every 60,000, because it's something that will keep the direct injection engine running better over time and I'm in the long-haul keeper game on this one. If I were in your position, with a non-free maintenance interval in the owner's manual and a small non-turbo japanese car that sits in my driveway more than on the road, I'd be sticking to the time/mileage and oil type in the manual like clockwork.
posted by davejay at 7:07 PM on February 11, 2014

TheSweethome has a motor oil review which touches on scheduled changes as well.
posted by Johnny Wallflower at 7:17 PM on February 11, 2014

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