Do you have to pre-fill an oil filter before changing?

Modern engines, advanced oil filters, and evolving maintenance practices create confusion around one simple question: should you pre-fill the oil filter? Let’s break it down and look at what really matters.

No, you don’t always need to pre-fill an oil filter before changing it. Runex Auto oil filters are designed to prime quickly, protecting your engine within seconds of startup. But in some cases, pre-filling can provide added peace of mind.

Many fleet managers, mechanics, and distributors wonder about this step. I want to explain when it matters, when it does not, and how Runex Auto oil filters support smooth and reliable engine performance.

Should you prefill an oil filter before installing?

Modern oil filters and engines have changed how we handle oil changes. The old rule about always pre-filling the filter may not apply today. But it still has a place in certain use cases.

You don’t have to pre-fill an oil filter before installation in most cars. Runex Auto oil filters feature advanced anti-drainback valves and efficient media, ensuring quick oil flow on startup. For heavy-duty engines, pre-filling helps avoid dry starts, which can reduce noise and wear.

When does pre-filling matter?

For light passenger cars, modern oil systems and high-quality oil filters like those from Runex Auto reduce the need for pre-filling¹. Our filters prime within seconds. But for larger engines — think delivery vans, fleet trucks, or agricultural machines — I recommend pre-filling. It prevents those dry first seconds after oil changes that can create unnecessary wear.

What does Runex Auto offer?

Feature	Benefit
Anti-drainback valve	Prevents oil from draining out of the filter, protecting during startup
High-flow media	Allows rapid oil circulation, reducing the risk of dry starts
Robust build	Withstands pressure surges common in larger engines

When I worked with a distributor serving fleet vehicles, they saw quieter starts and fewer warranty claims once they adopted this simple step. It showed customers they cared about long-term engine health.

Do I need to empty oil to change the oil filter?

This question comes up a lot, especially with fleet servicing teams. The fear is always about mess, contamination, or incomplete oil changes.

Yes, you should drain the old oil before changing the oil filter. This ensures no old, dirty oil stays trapped and that the fresh oil stays clean. Runex Auto filters are designed for clean removal and replacement when you follow this step.

Why draining matters

If you don’t drain the old oil, dirty oil could stay behind in the system. That can reduce the performance of your new oil filter. It can also shorten engine life. Runex Auto oil filters² are easy to remove thanks to their precise design. A clean oil change³ ensures that the filter’s full capacity and flow are put to use.

Steps for clean oil filter changes

Step	Purpose
Warm engine slightly	Helps old oil flow out smoothly
Fully drain oil	Removes contaminants
Replace filter with new Runex Auto oil filter	Ensures perfect seal and fit
Refill with fresh oil	Keeps system clean and protected

Over the years, I’ve seen that this careful approach helps reduce customer complaints about engine sludge⁴ and early wear.

Should you pour oil into a new filter?

This is where opinions often clash. Mechanics and fleet managers debate it at conferences, in shops, and online forums. The truth depends on the engine and the filter.

It’s not required to pour oil into a new filter before installing it, especially with Runex Auto oil filters. Our filters prime quickly. But for large engines, pre-filling the filter reduces dry start risk. It’s a small step that can make a big difference in customer trust.

When pouring oil helps

When I advise heavy-duty fleet clients, I often recommend pouring oil into the filter. This avoids dry starts⁵, which can create noise and stress components. Delivery vans and trucks benefit from this small effort. One distributor we worked with saw warranty claims drop after adding this to their standard oil change process⁶.

Runex Auto’s oil filter features

Feature	How it helps
Fast-priming design	Reduces need for pre-fill in most cars
Strong anti-drainback valve7	Keeps oil ready at startup
Large capacity	Handles higher oil flow of larger engines

This balance of features means you can trust Runex Auto oil filters to perform — whether or not you pre-fill them.

Can I fill oil without changing the filter?

Sometimes people want a quick top-up without a full oil change. Maybe it’s between services, or maybe they’re short on time. But is this a good idea?

Yes, you can fill oil without changing the filter, but it’s not ideal for long-term engine health. The filter still traps old debris. Runex Auto oil filters are designed for long life, but replacing the filter when adding oil keeps your engine cleaner.

When should you change the filter too?

Adding oil without changing the filter is okay in emergencies. Maybe oil levels dropped unexpectedly⁸. But I always advise clients to schedule a full change soon after. This keeps engines running at their best. Our filters at Runex Auto are built for durability, but even the best filter can’t clean forever.

Filter change and top-up best practices

Scenario	What to do
Low oil between changes	Top up, but monitor levels and schedule change soon
After heavy use or long trip	Change filter and oil together
Regular service interval	Always change both for best results

When I help fleet clients, I stress the long-term cost savings of regular full changes⁹. It reduces breakdowns and builds customer confidence.

Conclusion

Choosing whether to pre-fill an oil filter¹⁰ or when to change it can feel like a small detail. But small details build trust and protect engines. Runex Auto oil filters are designed for modern engines and demanding conditions. Our filters prime fast, protect during startup, and fit securely. But when in doubt — especially with heavy-duty engines — take the extra step. It shows your customers and partners that you care about their vehicles as much as they do.