Switching to Synthetic Oil After 100k Miles – Is It Safe?

There are a lot of misconceptions and opinions surrounding switching to synthetic oil after 100,000 miles. So what exactly is the truth?

Switching from conventional oil to synthetic is usually safe if your vehicle is properly maintained. However, be aware that in some instances there may be leakage issues with certain vehicles.

Is it Safe to Switch to Synthetic Oil Over Time?

Many people consider switching to synthetic oil once there vehicles actually reaches certain mileage, but are uncertain whether it is a safe thing to do.

The short answer to this question is yes, once you take the time out to take proper care of your vehicle and follow all manufacturer recommendations. Providing your car with regular service and maintenance should make switching to synthetic oil a easy thing to do.

One thing to be mindful of with synthetic oil is that it can expose existing leaks that were previously covered with sludge. This is especially true for older engines using rope-type oil seals or cork gaskets, which were once popular in the automotive industry.

Before switching to full synthetic oil, it’s essential that the pores and holes in your gaskets and seals be addressed. Otherwise, you could end up with a lot of oil leaking from your engine.

Switching to Synthetic Oil After 100k Miles

Is Switching to Synthetic Oil After 100k Mile a Good Idea?

If it’s a case where your vehicle has traveled 100k miles or more, chances are you’re considering whether switching to synthetic oil is a safe thing to do. It’s a contentious debate with plenty of myths and opinions surrounding it; here are some things you should consider before making the switch:

When considering whether it is safe to switch over to synthetic oil after 100k miles, your car’s maintenance history matters. If your car receives regular service and there are no leakages, then that should be sufficient information to allow the switch.

However, as mentioned above, switching to synthetic oil can potentially expose existing oil leaks by flushing out the gunk that had been sealing them. This could be an issue if your seals are old and brittle and already leaking. In order to avoid this situation, it is best to take your car to a mechanic and have any pores or holes in the gasket and seals filled.

Find Out More: Should You Use Synthetic Oil in Older Cars

What Happens When You Switch to Synthetic Oils?

Synthetic motor oil offers several advantages over conventional oil. It tend to has greater breakdown resistance, enhanced additive packages to prevent sludge buildup, and it provides better lubrication with a lower viscosity.

Synthetic oils are known to be thicker with greater temperature resistance, helping them flow and adhere to engine parts more effectively. This means synthetic oils can last longer when compared to conventional oils and reduce oil changes for older engines.

However, they can also pose challenges for some vehicles. In particular, old gaskets and seals may become vulnerable to leakage after switching from synthetic oil.

The thing is that synthetic oil molecules are smaller and more even-sized than traditional oil, meaning that they will pass through holes and pores in gaskets and seals more easily.


When it comes to cars with high mileage, drivers often turn towards synthetic oil in an effort to improve the engine’s performance. But there are a few questions that arise in this process.

One common question is whether or not switching to synthetic oil after 100k miles is a great option. The answer to this question depends on your vehicle and how it’s being used.

Synthetic oil after 100k miles is recommended if your vehicle is in good condition and you have been keeping up with recommended maintenance intervals.

However, it’s wise to consult a professional before switching over to synthetic oil. Doing so will guarantee your gaskets and seals are in optimal condition.

With that said, we think it’s best to avoid synthetic oil on engines with numerous leaks. Synthetic oils have the potential to reveal existing issues that had been covered up with sludge.