How often should I change the oil in my car?

Factual Questions
1

This seems like such an obvious topic of discussion that I’m sure it’s already been addressed, but the search function isn’t working for me.

I have a 2010 Prius coming up on 50K. The car wants me to change the oil and it’s almost 5K since the last change. I was brought up to change oil every 3K and that’s what I usually do, just forgot to do it this time around. But my wife’s Jetta says to change it every 10K and I’ve seen other places that synthetic oil (which I use in the Prius) only needs to be changed every 10K.

What’s the Straight Dope?

2

Few cars need an oil change every 3k miles these days (if any?). Stick to the manufacturer’s recommendations, but pay attention to variations with use - more frequent in dusty conditions for example.

3

Oil and engines are a LOT better than the days when a 3,000-mile change was the standard. If you’re running synthetic, ten to fifteen thousand miles is probably good. BMW and Porsche recommend synthetic (Mobil 1, iirc) every 15k miles or one year and lots of older drivers say that can’t be right, but everyone that’s had their oil done by Blackstone Labs or similar have come back with reports saying the oil was still good.

I change my motorcycle’s oil every 3k, but that’s because I still run dino oil and the engine is from 1978, so it breaks down sooner and picks up more contaminants. I’ve tried running synthetic in an old engine - it wasn’t pretty.

4

Following the manufacturer’s recommendation will work fine.

5

As a rule of thumb, non-synthetic API SN oil with a good filter is good for 5000-6000 miles in most normal US-made cars, excluding late-model GM.

However, you have to pay attention these days to the specs in the owner’s manual, especially if you have a European car. For example, my 2010 VW Passat calls for VW 502.00 oil, which is NOT the same thing as regular old Quaker State or Valvoline. Mercedes-Benz cars call for their own spec oil, as do Porsche and BMW/Mini. Also, many new GM cars require the DEXOS 1 spec, which is also NOT the same thing as garden-variety API SN.

So your Jetta almost certainly requires some sort of VW oil- the only one you’ll be able to find easily is the Mobil 1 0w-40 oil, which at least where I live, is available at Wal-Mart. The vast majority of other 502.00 oils are mail-order or sold at dealerships.

I imagine your Prius probably uses some kind of low-viscosity oil- like a 0w-20, which is readily available, but I don’t know about any Toyota-specific specs that they may require.

6

RTFM
Read the freakin manual.
The guys that designed your car know more about it than anyone on an internet message board.
When reading pay particular attention as to what qualifies as severe conditions. It is quite likely your normal commute falls into severe duty.
As has been mentioned use the oil the car maker specifies. Not all oils are the same and the wrong oil can cause premature wear.

7

The manual for my Honda Fit does not recommend oil changes at specific mileage intervals. Instead, there is an oil life indicator on the dashboard and it recommends getting the oil changed at 10-15% of useful life. Your Prius may have something similar. I don’t know why your car is advising an oil change at less than 5,000 miles, but you should change it.

8

We too have a Prius. I was raised with the thinking of 3k mile fluid changes, and I am very anal with my vehicle maintenance.
We have a factory vehicle maintenance plan that came with the first Prius when we bought it new. I went to the dealer insisting the first oil change needed to be done at 1000 miles. The service writer said that the “Break in” change was no longer necessary on modern engines. I had to pay for the service out of pocket, but it made me feel better. Next, I wanted to change the oil again 5k miles later. I always use Mobile 1 oil on 5k mile changes, but I was again told that the service plan only paid for service at 10k mile intervals. I again paid extra to do the 5k mile changes. The service manager was patient with the old guy with old ways. He said I have to get over the old school thinking of 3k and 5k service intervals and that engines and oil are both very much different and improved since even the 90’s.
On our second new Prius I left the original factory fill oil in for the first 10k miles. It was killing me to think of the oil being in for so long, with no change even for the break in period. We’re now at 20k miles and just now due for what will be only the second oil change the car has ever known. And you know what? The car and engine are doing just fine.
Oil is different and engines are different. 10k mile intervals are fine if that’s what the factory schedule says. I just needed to evolve with technology.

9

Exactly, except that in general, the 10,000 mile intervals specified in owner’s manuals also require particular oil- BMW’s LL (long life) spec, or VW’s 502.00 spec, or the DEXOS specs. These are almost always synthetic oils of some kind.

I’d be willing to bet no manufacturer specs a 10,000 mile interval on regular old API SN oil, so it pays to check the manual if you have a high recommended interval.

There are plenty of people who see 10,000 mile oil change and then fill up with regular old Pennzoil and mess their engines up because they didn’t realize that they needed some kind of specific spec long drain interval oil.

10

Seriously, follow the manufacturer’s recommendation. They have no reason to advise you to skimp on maintenance, and plenty of good reasons to tell you how to keep the car running well. They’re on the hook for any engine failure during the warranty period. So if they tell you to change the oil less than you should, they will lose a lot of money on warranty repairs. Additionally, in the long term they don’t want a reputation for poor reliability.

11

This.

It may be a surprise to discover what “normal” means to car makers.

When it comes to warranty issues, it would be safest to assume “normal” means a car in mint condition with fresh oil and perfect fuel piped into the engine from the refinery lab next door, and running for weeks non-stop on rollers with the cruise control set at 42 mph so the transmission’s in lockup and the RPMs at 1,100, in a computer-chip-fabrication clean room at a consistent 68°F with humidity of 30 per cent. Anything else could be “severe.”

Go by the car’s dashboard oil-change indicator.

I’m in Canada. All figures are changed from metric: I run synthetic motor oil, Mobil 1. Last spring I changed the oil, and 7,250 miles-and-change later, in early winter, the oil-change computer said change the oil. The computer is set up for conventional oil, so I waited until the indicator hit 0-per-cent remaining.

I sent a sample of the old oil to Blackstone Labs, because I wanted to know the difference between the oil-change computer’s commandment that in my car is set for conventional oil and the length I could extend the oil-change interval with synthetic.

Blackstone replied that the oil had so much of its additives remaining and so few contaminants (listed and quantified) that I should be able to extend the next change to the 9,000-mile mark.

However, this winter has been particularly brutal, with –20°F to –35°F for weeks, then months, on end. The oil-change computer is counting down the percentages to the next oil change much, much faster than it did during the summer — it really is severe service — so I’m not going to wait any extra time to change the oil, despite it being synthetic. Any extra mileage I could achieve would be shortened, as well. But by how much? Who knows? Blackstone would, but the lab’s results aren’t instant and cost money.

The oil-change doohickey computes the oil-change interval not by any direct measurement of the oil but by the engine’s temperature over the long term, whether it achieved proper warm-ups, the ambient temperatures, the length of trips and so on (the driver’s manual is in the car, so I’m not going out to read it).

Blackstone’s confirming my guesstimate and the computer’s faster oil-change-countdown rate during this very cold winter give me more confidence that the computer’s oil-change countdown is accurate.

It may be worth mentioning that I don’t use the cheapest oil filters on the shelf.

The forums at bobistheoilguy.com (I am not a member and have nothing to do with it) provides lots of information.

12

Depending on the car some do take measurements of the oil condition (acidity IIRC) and factor that into the algorithm.

13

That’s much better.

14

My Citroen C5 has a recommended oil change every 12,500 miles with the specified Total Quarz 9000 5W30 Fully Synthetic. I change it at around 8,000 miles or less. This is with the 2.0 Litre HDi engine.

There is a variant, a 1.6 HDi developed in conjunction with Ford.
The recommended oil change with the oil specified being Total Quartz 900 futur - a low sulphur, low ash oil, is around 16,000 miles.

This has proved to be a disaster with the change being far too generous in conjunction with a very fine filter in the turbo oil feed that clogs up very easily with the particles accumulated during the protracted oil change period.

Ruins the turbo and practically takes the engine and exhaust system with it. Complete engine rebuild, replace turbo and full exhaust including cat and DPF. A very expensive venture.

Changing the oil at 7,000 miles precludes all that pain and heartache, along with the shock to the wallet.

15

My wife’s Subaru recommends full synthetic every 7500 miles. I’m grumbling about it but doing it anyway.

16

Use synthetic and change around 7K.

17

If the car is still under warranty, change the oil when Toyota says you should. Otherwise, if anything happens, it might not be covered.

18

I use dino and have had several vehicles go well into the 250-300+K miles on original engine and major components.

I am also of an era when the 3,000 mile oil change was the norm and I’ve relaxed somewhat on that but still am compelled to do oil changes more frequently than recommended. About 5K between changes. I take my vehicles to a local independent shop that charges $19.95 for an oil change. They also do no-charge tire rotation, check every fluid, check tire pressure, and will address any concerns or answer any questions I have for no extra charge. In over ten years, they’ve yet to try talking me into a single thing and in fact have talked me out of pricey fixes, or suggested cheaper work-arounds.

They are actual mechanics at a local full-service shop that services our local police and city vehicles as well as race and high-performance cars, not minimum-wage oil-changers at a national chain. As a non-mechanically inclined person who owns three vehicles (for work, mostly) I really need to trust a shop.

$20 every three or four months for fluid changes and a general look-see of the operating system is a freaking bargain, if you ask me. It’s not like you’re going to harm your car by doing too-frequent oil changes.

19

For clarity’s sake, it is important to distinguish between manufacturer’s recommendation and dealer’s recommendation (here “dealer” also includes independent oil-changing services like Jiffy Lube). The dealer makes money every time they change your oil, and they’d tell you to change it every 1000 miles if they thought you’d play along. OTOH, the manufacturer - the company that actually designed and built your car - does not make money every time you change your oil. They are motivated to give you the most economical ownership experience, and they have the research data that justifies the oil change interval that they specify, which is often 6000 or more miles (it may be shorter for “harsh/severe” service, which includes a lot of short trips in cold weather).

TL,DR: follow the manufacturer’s recommendations listed in the service manual that came with the car - not the dealer’s (or anyone else’s) recommendations.

20

Do you know if anyone is actually doing this now? BMW tried such a system in the 1990s but dropped it due to problems. They still have an oil service indicator, but all i does now is measure how many gallons of fuel you’ve used, with the target being 15,000 miles/ highway mpg.