Synthetic Oil Change Interval: How Often Should You Change Synthetic Oil?

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Following the correct synthetic oil change interval is an extremely important thing when it comes to keeping your car’s engine running nice and smooth for a long time.

But we all know that synthetic oil does cost some good money so we don’t want to change it prematurely, right?

We also don’t want to extend its service life too long and end up damaging the engine.

So, let’s find that sweet spot.

How often should you get an oil change?

For those who have no more than 1 minute to get an answer to this issue here is your short answer:

  • Synthetic oils have an average 7000 miles of life in them.
  • Full synthetic oils have around 10000 miles worth of proper lubrication in them.

But what is that about “synthetic” and “full synthetic”? Well, for that you’ll have to stick with us a little more because this is really worth diggin’ into.

Grab a drink. Let’s do some real talk.

Among all members (editors, friends, family, and contributors) of Gear4wheels we’ve owned many, many cars (and quite a few motorcycles, one snowmobile, two ATV’s, four 49cc scooters, and other uncontestable things with wheels) and we’ve always followed the “3000 miles or 3 months” oil change rule. And you’ve probably had to.

Now things have changed a little bit in the oil scene and synthetic oils are becoming the norm. Manufacturers now recommend longer oil change periods as long as 15000 miles (In Europe, some manufacturers that recommend Castrol Longlife go up to 20.000 miles) and there is a lot of discussion on the topic.

We are going to cover one by one the factors that will determine how long is your oil going to live before you have to put it back on a can and bid farewell and reveal why we do not follow that rule anymore.

The 3000 miles rule.

This applies to conventional mineral oils.

They are overall low-performance oils even when new. Check the following image (Courtesy of Pennzoil) in which they are comparing Synthetic Vs Conventional oil.

synthetic oil flow low temperature

They let both oils run at the same time. Synthetic runs quickly and smoothly and conventional takes longer to touch metal. It looks thicker. And those are both brand new oils…

This image shows used vs new oils both (courtesy of Engineering Explained)

synthetic oil flow vs regular oil flow

You can very quickly see that whilst all three other oils ( new and used synthetic, and new conventional oil) have already touched the metal and are flowing, used conventional oil is barely dripping from the test probe.

The image is quite self-explanatory. Conventional oil loses properties with time and use and has to be replaced frequently to ensure that engines running it are actually well lubricated. 3000 miles has always been the rule. Good.

So what happens with synthetic oil then?

Here is the tricky part. There are semi-synthetic oils and full synthetic oils. They have different lifespans as how many miles can you run them before they turn into solid grease.

Synthetic and Full Synthetic

Whether oil is labeled as synthetic or full synthetic depends on one key factor: The used base oil. The American Petroleum Institute (API) has divided them into 5:

oil base stocks
  • Group I, II, and III are refined from petroleum crude oil.
  • Group IV is polyalphaolefins and Group V is Esters. Only oils that use these two groups as a base are fully synthetic oils.

Synthetic oil change interval: What manufacturers say

Remember that short answer we’ve given at the beginning of this post?

​Synthetic oils have an average of 7000 miles of life in them.

​Full synthetic oils have around 10000 miles worth of proper lubrication in them.

That’s what most oil brands tell about their oils. Some car manufacturers elongate this a little more (Jaguar recommends 15.000 miles for full synthetic) but they also say “Under ideal conditions” which 99% of the time aren’t the real conditions.

Factors That Age Oil Quicker

So as we have mentioned, those 3 numbers, 3.000, 7.000, and 10.000 miles are not set in stone. Take them as a guideline.

There are many factors that will have an impact on the oil and likely make it lose properties quicker. Lets see a few:

  • Diesel Engines: Diesel is a less refined product than gasoline. It produces more soot and acid by-products.
  • High-Mileage Engines: Engines with a lot of miles on their back generate more blow-by gases and unburnt fuel that gets into the crankcase.
  • Turbocharged Engines: Turbos can spin at over 100.000 rpm. Once you shut off the engine, it still spins for a while (although you should leave your engine to rest a few seconds after you stop before you shut it off to let the turbo reduce its spin back to idle) the high heat built-in bearing surfaces may cause oil to crack forming hard carbon deposits and hydrogen.
  • Short trips: Especially in winter. The engine doesn’t have time to reach the optimal working temperature. Low operating temperatures cause moisture and byproducts of combustion to build up in the oil. This will generate waste deposits and acid in the engine that can lead to faster wear on pistons, cylinders, bearings, and crank journals.
  • Your driving style: The more aggressive you drive (high revs, quick accelerations etc) the more you are asking out of your oil.
  • Road dust: Driving in very dusty environments will make your car suck a lot of dirt. A good air filter will retain everything that is bigger than a micron, but everything else will pass through and go into the oil. A good quality oil filter will retain all those particles but this will indeed shorten the life of the oil.
  • Towing/Heavy loads: Increased duty, higher temperatures that increase metal wear. Wear metals cause premature oxidation, sludge, acids, and deposits.
  • Bad Oil Filters: The oil filter is a key component of the lubrication system. They accumulate all the nasty stuff such as dirt, water, metal particles, etc that gets into the oil (the very same particles we’ve just seen that aging oil quicker) Bad oil filters barely filtrate such harmful agents, so make sure you are using the best oil filter on your car.

So will a diesel pickup with 130.000 miles that are usually used to bring construction materials to Uncle Ben’s farm in Omaha be good with 8.000 miles between oil changes? Hell no.

Let’s be clear. There is no magic calculator in which you input every variable and it gives you an accurate number of miles in between oil changes.

Our recommendation for you is to get the best synthetic motor oil, the best oil filter, and then take into consideration all those factors and think “Ok so if this oil is supposed to last 10.000 miles, I do a lot of short trips, my car is gasoline and it hasn’t got a turbo and I do REALLY care about it lasting a long time… let’s do 6.000 miles from change to change” for instance.

We encourage you not to drive over the “recommended” miles. And since there is a lot of discussions lately on why manufacturers are constantly changing their recommendations, we also want to share our take on this trend.

From 3000 miles to 20000 and back to 10000. What’s changed and why?

So the first thing is clear. Synthetic oils last longer and overall perform better. But 15000 or even 20000 miles is pushing it way too much. BMW recommended 15000 miles or 24 months around 2013… but then for all 2014 models and applying to older cars too, they changed to 10000 miles or 12 months. Why that change of mind?

A high rate of failure of mechanical parts at low mileage, essentially.

Car manufacturers are responsible for as long as the car is on warranty. Short-term problems are their problems. But long-term problems are their profit.

So basically once they saw that their oil change schedule was costing them a lot of money, they decided to shorten it.

Same with break-in oil changes. It is costly for manufacturers to do it after 1000 miles. They will refuse to conduct it, literally. But that is the moment in which you should do it.

About Computer Oil Life Monitors

You might think “Hey my car comes with Oil Life monitor built-in, I know when to change my oil”  and it is a fair thought. You’ve paid for that feature, don’t you? But here is the trick to that.

Most systems (GM, Ford, PSA to name a few) calculate the oil life based on data collected from different engine sensors. The engine computer will calculate based on an algorithm and all that data and provide a “result”.

It is pure software. Ever tried to lose weight and followed something that looked great in the book but the results weren’t as expected? Pretty much the same.

There is no sensor actually in your oil pan. So with no actual readings being taken straight from the oil, you cannot know precisely what is going on. Just an “estimate”.

Some BMW and Mercedes Benz do have a sensor in the oil pan, but like every other sensor, they can malfunction and get contaminated by a lot of agents, providing wrong lectures.

As a quick footnote, a sensor that’s malfunctioning won’t light the “Check Engine” pilot unless the data it provides is off-range.

If the measure is “reasonable” for the onboard computer, it won’t turn the dreaded light on. Even if it is wrong. So, yeah, they give you some information but don’t take it as a final word.

By the way, if you’re serious about your car and want to discard such problems as sensors working “fine” but actually measuring cows instead of ducks, get an obd2 scanner, one of the smartest investments you can do.

Environmental Issues

One liter of oil contaminates one million liters of water. Let that sink.

Service stations will collect used oil, whether they have changed it or not. In the end, they sell it at a quite good price so it’s worth the effort. Unnecessarily frequent oil changes will have a negative impact on the environment and we should bear that in mind.

However, disposing of the high contaminant waste in the right place should be our #1 concern.

Discover The Best Synthetic Oils

I’ve conducted some MASSIVE research to craft a list of the top synthetic motor oils in the market.

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Choosing The Right Synthetic Oil

As much as you know how often to change your synthetic oil, the big question is, are you using the right synthetic oil for your engine? This is an important factor since it directly affects the performance of any car’s engine. Therefore, some important factors to consider as you shop for your ideal synthetic oil.

Type

There are two types of oil;

Full synthetic – that features a unique molecular structure and additives that promote optimal wear protection and engine performance. This oil type gets created in a lab, and its advantage is that it doesn’t include impurities found in conventional oil. Furthermore, some brands use a blend of anti-wear and cleaning additives to enhance the motor’s performance.

Synthetic blend – a mixture of conventional and synthetic base oil. Brands create this mixture to create a solution for customers seeking better engine performance and protection. However, they do not offer the same protection as the full synthetic type. This synthetic blend type also offers additional benefits compared to conventional oil.

Viscosity

The ideal viscosity grade varies and depends heavily on the driving conditions. If your car operates in a hotter climate, a 5W-30 synthetic oil is a right option to try. A 5W-20 or 0W-20 grade is ideal for keeping the engine performing optimally for those operating in cold weather or arctic severe conditions. However, those commuting in average driving conditions can get the 5W-30 option.

Additives

Brands tend to include various components to enhance certain properties. For example, some manufacture synthetic oil that doesn’t get too thin when exposed to high temperatures. Others choose to use detergents as cleaning agents to remove sludge and other deposits from the automobile engine. It is therefore important to determine your preferred additives and their benefits to help you determine your ideal option.

Compatibility

The general rule of thumb is to ensure you use the same synthetic oil when conducting a refill. This is to ensure that it is fully compatible with the existing one. Therefore, the best way to do this is to source your synthetic oil from the same brand. But what if you wish to switch up to a better product? Ensure that you completely drain the existing oil, using the drain plug, before refilling your preferred choice.

Application

Synthetic oil packaging contains labels showing the specific application it is designed for. For instance, you’ll find some indicating higher mileage, diesel engines, extended performance, and many more. The right choice depends on your engine’s and vehicle’s condition.

Final Thoughts

The right synthetic oil change interval will keep your engine properly lubricated, ensuring the right performance.

It will save you a lot of money on expensive repairs.

Just be sure to change your oil filter at the same time, follow our recommendations for a successful change if you do it yourself, and ensure that you dispose of the used oil at the right place.