Earlier this week, Nissan posted up a Technical Service Bulletin relevant to the appropriate oil filter to use on the VR30 engine in the New Z. While the TSB appeared to cause more confusion than clarification. Fortunately we’ve got experts in our midst to help straighten out the info.
There had been a lot of discussion (before and after the TSB) about which filter to use, and how much the pressure relief setting affects performance and engine reliability. Thankfully, Ty from AMS Performance is here to clear up some misconceptions about oil filters and their pressure relief valve ratings, so I’ll let Ty break it down from here:
Pressure Relief Valves: What They Do
The pressure relief valve in your oil filter is a fail-safe. If your filter becomes clogged and oil pressure spikes beyond the valve’s threshold, it allows oil to bypass the filter entirely. This ensures your engine doesn’t get starved of oil, and prevents any chance of the oil filter splitting open due to pressure.
But here’s the key point: If your oil filter is clogging to the point where the pressure relief valve is really coming into play, you’ve likely got much bigger problems to deal with. A healthy engine running clean oil and a properly maintained filter shouldn’t normally trigger this fail-safe.
Why the Relief Valve PSI MATTERS (OR DOESN’T?) IN A VR30
The pressure relief bypass settings between the original OEM filter and the new OEM filter suggested in the TSB differ significantly: 98 kPa (14.2 PSI) for the original OEM filter versus 250 kPa (36.25 PSI) for the new one. With the smaller OE filter and its lower bypass setting, the bypass could theoretically open during normal driving conditions, especially with higher than 0w-20 oil viscosities or increased engine demands from added horsepower or higher than stock RPM range.
When tuning these vehicles, RPM limits are often raised slightly, and the engine is allowed to reach higher RPMs more quickly. This rapid increase in RPM can create conditions where the relief valve is repeatedly triggered, especially with the old filter’s lower bypass setting, potentially compromising oil filtration.
This is why we recommend the larger WIX filter with a 27 PSI bypass setting. Its larger size increases oil flow capacity, reducing the chance of the bypass opening under normal or high-performance conditions. However, the new OEM filter, while having a higher bypass rating, appears to still be smaller in size, which raises concerns about its flow capacity and the likelihood of meeting the same bypass conditions under performance driving.
By focusing on using a larger filter with an appropriately higher bypass setting, you can better support increased oil flow and filtration needs for high-performance applications.
Focus on Filter Size and Maintenance
Instead of getting overly concerned about the exact pressure relief rating of a filter, your attention is better spent on these factors:
- Use the Largest Filter Possible – A larger filter increases oil flow capability, allowing for better filtration without compromising flow. This is especially critical for performance engines or applications where the oil system is working harder. A larger filter also has more capacity to hold debris, reducing the chances of it clogging prematurely. For the GTR, we manufacture a CNC machined adapter plate that allows for much larger sized filters to be used on our built VR38 engines.
- Use a High Quality Filter – A high quality filter designed for motorsports usage is the best choice for high horsepower modified vehicles. Filter media, number of pleats, and overall materials and design play a huge part in filter efficacy. Believe it or not, WIX makes fantastic filters, and we utilize their Racing line of filters for many of our builds. Even NASCAR uses them!
- Change Your Filter Regularly – No matter how well-designed or large your filter is, it won’t last forever. Regular oil changes and filter replacements are the best way to keep your oil system clean and your engine functioning optimally. By changing your oil and filter more frequently, you’re effectively reducing the risk of clogging to the point where the pressure relief valve even becomes relevant.
The Takeaway
- Prioritize the largest filter that fits your application for increased filtration capacity and oil flow.
- Stick to an accelerated oil change maintenance schedule.
- If your filter clogs enough to trip the relief, it’s time to diagnose and fix the actual problem causing the excessive debris in your engine oil.
[editor note:] I’ve always answered the “which oil is best?” question very simply: CLEAN oil is best. If you’re adhering to 3-4k mile oil change intervals, the minor differences in oil base and additives becomes largely irrelevant. Of course, there are as many opinions as there are brands, and people will literally argue themselves silly over which brand is best – but again, frequent oil change intervals with the correct synthetic oil in the recommended viscosity makes the entire argument irrelevant… and all the brand loyalty in the world won’t matter. Just change your oil and use the right filter.
By focusing on these principles, you’ll ensure your engine stays healthy and reliable without sweating minor differences in filter specs. HUGE thanks to Ty from AMS for popping in and clarifying this issue. Share this article with your friends and happy Z motoring!