Do you have to prime your oil filter before changing it?

When it comes to oil changes, there’s a lot of debate about whether you really need to prime your oil filter first. Some swear by it, others say it’s unnecessary. But the truth depends on the type of engine and the quality of the oil filter you’re using.

You don’t always have to prime your oil filter before installation. Most modern engines and premium filters like Runex Auto’s oil filters reach oil pressure within seconds, making pre-filling optional except for certain diesel or heavy-duty applications.

Even though it’s a small step, understanding why and when to prime your oil filter helps extend engine life and avoid unnecessary wear — especially if you’re working with older engines or larger filters. Let’s look deeper into how it works and when it matters most.

Do I need to prime my oil filter?

Many car owners and even mechanics think priming is always necessary. It’s not. The idea of priming — or filling your oil filter with oil before installing it — comes from older engines that lacked fast oil circulation. Today, things have changed.

With modern oil filter technology, such as Runex Auto’s anti-drainback valve design, priming is often unnecessary because oil pressure builds almost instantly after startup, ensuring full lubrication within seconds.

Dive Deeper: When priming still matters

Modern filters, especially those produced by Runex Auto, include anti-drainback valves¹ that prevent oil from draining back into the sump when the engine is off. This means the filter already holds oil near the engine, making priming redundant in most cases. However, there are exceptions worth noting.

Engine Type	Priming Recommended?	Reason
Gasoline Passenger Cars	❌ Usually not needed	Fast oil circulation and advanced valves
Diesel Trucks	✅ Yes	Larger filters and slower oil pressure build-up
Racing Engines	✅ Yes	Higher demand on lubrication at startup
Classic Cars	✅ Often	Older designs without check valves

I once had a client with an aging diesel fleet². His team complained about loud rattling noises after oil changes. The issue? They skipped priming. Once they started pre-filling the filters halfway, the startup noise disappeared. That moment reminded me that even a small step can build big trust — both in machines and in products.

What should be done to a new oil filter before installing it?

Installing a new oil filter isn’t just about tightening it in place. It’s about setting it up right from the start so it seals properly and functions as designed.

Before installation, always inspect the new filter’s gasket, apply a thin layer of clean engine oil, and make sure it’s seated evenly. This prevents leaks and ensures smooth removal during the next oil change.

Dive Deeper: Proper prep equals better performance

Every Runex Auto oil filter goes through precision gasket molding and leak testing³ before packaging. Still, the installer plays a big role in final performance. Here’s the correct way to prepare your new filter:

1. Inspect the gasket – Make sure it’s free of dust or debris.
2. Lubricate it lightly – A thin film of clean oil prevents sticking and tearing.
3. Check the filter base – Remove any old gasket material left behind.
4. Tighten by hand only – Never use a wrench unless specified.

Step	Purpose	Common Mistake
Gasket Check	Ensures clean, smooth seal	Skipping visual inspection
Oil Lubrication	Prevents gasket from binding	Using dirty oil
Base Check	Ensures flush mounting	Forgetting old gasket
Hand Tighten	Prevents over-torque damage	Using excessive force

At Runex Auto, we design our filters for easy installation and removal⁴, but we still see field failures caused by dry gaskets or overtightened filters. Spending an extra minute here can save hours of troubleshooting later.

Can I replace my oil filter without draining oil?

This question pops up more often than you’d think — especially among those trying to do quick maintenance between full oil changes. The short answer: it depends on your vehicle’s design.

In most vehicles, replacing the oil filter without draining oil is possible, but some oil will spill. However, if you’re using a Runex Auto filter with a solid anti-drainback valve, oil loss is minimal and manageable.

Dive Deeper: How oil system design affects this

Most engines keep the filter mounted vertically or at an angle, meaning gravity pulls some oil down when the filter is removed. That’s normal. A well-designed anti-drainback valve⁵ helps retain oil in the filter and upper galleries. This not only prevents dry starts but also allows quick filter swaps with minimal mess.

Filter Mount Position	Oil Drainback Risk	Notes
Vertical (Top-Mounted)	Low	Ideal for quick swaps
Horizontal	Medium	Oil may spill when unscrewing
Upside-Down	High	Always drain oil first

If you’re using a Runex Auto filter⁶, the silicone anti-drainback membrane seals effectively, even under pressure drops. In my experience, I’ve done mid-cycle filter swaps on smaller fleet cars with less than a cup of oil lost. Still, I always advise topping up afterward — precision matters when maintaining lubrication balance.

Why do you put a thin film of oil on the new oil filter gasket?

Some mechanics call this step “old-school,” but it’s one of those timeless habits that continues to prove its worth. The oil doesn’t just lubricate — it protects.

Applying a thin film of oil on the gasket prevents sticking, ensures an even seal, and makes the filter easier to remove during the next change. It’s a simple yet critical step to avoid gasket tears or leaks.

Dive Deeper: Science behind the seal

The gasket on a Runex Auto oil filter is made from high-durability nitrile or silicone rubber⁷, depending on the product line. These materials provide excellent resistance to temperature and pressure changes, but they need lubrication to seat properly against the engine’s mating surface.

Material	Temperature Resistance	Flexibility	Ideal Use
Nitrile Rubber	Up to 120°C	Medium	Standard cars
Silicone Rubber	Up to 200°C	High	Diesel, racing, and high-heat applications

Without that light oil film, the gasket might twist as it’s tightened, creating micro-tears or uneven contact. This often leads to small leaks — the kind that are invisible at first but slowly build up residue. I’ve seen many filters returned under warranty only to find dry gaskets⁸ as the culprit. It’s a two-second step that eliminates hours of rework.

Conclusion

Priming an oil filter⁹ isn’t always necessary, but preparation always is. Modern filters like those from Runex Auto are built to deliver instant oil flow, strong sealing, and lasting durability. For older engines or heavy-duty trucks, a bit of pre-filling can still make a difference. Whether you’re a mechanic or a fleet manager, attention to small details — from lubricating gaskets to checking valves — defines long-term reliability.

In short, good maintenance is less about ritual and more about understanding. And with the right filter, you can trust your engine to perform the way it should — every start, every mile.