Is this BMW billet oil filler cap a full replacement or a cover?

The MMX BMW billet oil filler cap is a complete OE replacement CNC-milled from a single block of 6061 aerospace aluminum — not a cover that clips over the factory plastic cap. It arrives pre-assembled with an OE-specification internal valve, spring, Viton O-ring, and locking mechanism, so there are no components to transfer from the factory cap. Remove the old cap, fit the MMX unit, done.

What is the difference between S58 and B48E compatibility?

The S58 is the 3.0L I6 twin-turbo engine in the G8x M2, M3, M4, X3 M, and X4 M. The B48E is the higher-output variant of the B48 2.0L I4 turbo found in the F40 M135i, M235i, 128ti, X2 M35i, and MINI JCW models. This BMW billet oil filler cap is compatible with both engine families. Standard B48-powered models (without the E suffix) use a different cap fitment and are not compatible.

What does the internally sprung locking mechanism do?

The internally sprung locking clip ensures the BMW billet oil filler cap seats securely and delivers a positive click-fit confirmation on every installation. This eliminates the risk of under-tightening — a common cause of oil seepage on aging OEM plastic caps where the original spring and clip have degraded — and confirms correct fitment without requiring over-tightening.

Will the anodized finish hold up in the engine bay?

Yes. The gloss black anodizing is applied directly to the aluminum surface, not painted on, giving it resistance to heat, oil, and the cleaning products typically used in engine bay detailing. It will not peel, flake, or fade under normal engine bay conditions.

Does this fit xDrive models?

Yes. The MMX BMW billet oil filler cap fits all xDrive variants of compatible S58 and B48E models, including the M3 Competition xDrive, M4 Competition xDrive, X3 M, and X4 M.

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BP PRICING DIFFERENCE

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Description

MMX Billet Oil Filler Cap for BMW and MINI with S58 and B48E Engines

BMW billet oil filler cap from MMX Performance is a complete OE replacement for the factory plastic oil filler cap on S58-powered M2, M3, M4, X3 M, and X4 M models and B48E-powered BMW 128ti, M135i, M235i, X2 M35i, and MINI JCW variants CNC 5-axis milled in the UK from a single block of 6061 aerospace-grade aluminum, hand-polished, and finished in MMX gloss black anodizing. Unlike cosmetic stick-on covers, this is a full OE replacement pre-assembled with an OE-specification internal valve, spring, and Viton O-ring true plug-and-play with no components to transfer from the factory cap. An internally sprung locking mechanism delivers a secure, precise click-fit on every installation, eliminating the under-tightening and oil seepage risk associated with aging OEM caps, while a generous grip area makes removal and refitting clean and effortless during oil changes. Part of the MMX engine bay billet cap lineup; integrates directly with other MMX cap upgrades for a coordinated engine bay finish.

Features

Full OE replacement CNC 5-axis milled from a single block of 6061 aerospace-grade aluminum
Gloss black anodized finish for long-term corrosion resistance
Pre-installed OE-specification internal valve and spring no component transfer from factory cap
Pre-installed factory-spec Viton O-ring for a precise, leak-free seal
Internally sprung locking mechanism for a secure click-fit on every installation
Generous grip area for easy removal and refitting during oil changes
Part of MMX’s engine bay billet cap lineup
Designed and engineered in the UK

Applications

BMW:

BMW 128ti: F40 | 2020-2024
BMW M135i: F40 | 2020-2024
BMW M2: G87 | 2023-present
BMW M235i: F44 | 2020-2024
BMW M3: G80 | 2021-present
BMW M3 Competition: G80 | 2021-present
BMW M3 CS: G80 | 2023
BMW M4: G82, G83 | 2021-present
BMW M4 Competition: G82, G83 | 2021-present
BMW M4 CS: G82 | 2025
BMW M4 CSL: G82 | 2023
BMW X2 M35i: F39 | 2019-2023
BMW X3 M: F97 | 2019-2024
BMW X4 M: F98 | 2019-present
MINI Clubman JCW: F54 | 2019-2024
MINI Cooper JCW: F60 | 2015-2024
MINI Cooper JCW GP: F56 | 2020
MINI Countryman JCW: F60 | 2019-2023

Notes

Compatible with S58 and B48E engines only. B48E is the higher-output variant of the B48; standard B48 models are not compatible.
Also fits xDrive variants of compatible models
Sold as a single cap

Frequently Asked Questions

Is this BMW billet oil filler cap a full replacement or a cover? The MMX BMW billet oil filler cap is a complete OE replacement CNC-milled from a single block of 6061 aerospace aluminum — not a cover that clips over the factory plastic cap. It arrives pre-assembled with an OE-specification internal valve, spring, Viton O-ring, and locking mechanism, so there are no components to transfer from the factory cap. Remove the old cap, fit the MMX unit, done.
What is the difference between S58 and B48E compatibility? The S58 is the 3.0L I6 twin-turbo engine in the G8x M2, M3, M4, X3 M, and X4 M. The B48E is the higher-output variant of the B48 2.0L I4 turbo found in the F40 M135i, M235i, 128ti, X2 M35i, and MINI JCW models. This BMW billet oil filler cap is compatible with both engine families. Standard B48-powered models (without the “E” suffix) use a different cap fitment and are not compatible.
What does the internally sprung locking mechanism do? The internally sprung locking clip ensures the BMW billet oil filler cap seats securely and delivers a positive click-fit confirmation on every installation. This eliminates the risk of under-tightening a common cause of oil seepage on aging OEM plastic caps where the original spring and clip have degraded and confirms correct fitment without requiring over-tightening.
Will the anodized finish hold up in the engine bay? Yes. The gloss black anodizing is applied directly to the aluminum surface, not painted on, giving it resistance to heat, oil, and the cleaning products typically used in engine bay detailing. It will not peel, flake, or fade under normal engine bay conditions.
Does this fit xDrive models? Yes. The MMX BMW billet oil filler cap fits all xDrive variants of compatible S58 and B48E models, including the M3 Competition xDrive, M4 Competition xDrive, X3 M, and X4 M.

About MMX Performance

MMX Performance is a UK-based specialist in performance parts for BMW and MINI vehicles, crafting high-quality upgrades that blend precision engineering, rigorous testing, and motorsport heritage. Driven by enthusiast culture, MMX designs its products in the UK and puts them through track validation to ensure durability, fitment accuracy, and on-road performance. Their catalog spans drivetrain components, spacers, hardware, and chassis enhancements, all tailored to elevate both the driving experience and visual appeal of BMW and MINI models.

Additional Information

The Bulletproof Automotive website contains many thousands of products purchased in multiple different currencies. All of the prices are entered manually and accurately at the time of entry. Due to the consistently fluctuating international exchange rates, at times prices may not be able to be honored at their original intended rate. We apologize for any inconvenience this may cause, unfortunately our website is unable to compensate dynamically for what can at times be volatile changes in the cost of items due to currency values fluctuating, changes in prices from suppliers, changes in shipping and import duties, and other factors. Rest assured that any order you place on line will be at zero risk to you in this area. If in the event your order cannot be fulfilled at the original intended website price we will offer you a 100% refund, no questions asked. We will continue to do our best to maintain updated prices and we will always continue to offer our price match guarantees as well to ensure our prices are always the best for you. In short, prices may change without notice. It is always advised to give us a call prior to placing your order online to confirm availability and to confirm current pricing.

Shipping Policy

Items that are in stock in the US, either at Bulletproof’s warehouse or at a supplier’s warehouse, are generally delivered within 7-10 days. Special order items from overseas take considerably longer. As a courtesy Bulletproof offers delivery estimates to our customers which take into consideration manufacturer availability and shipping schedule. These estimates represent our best guess based on previous orders from the manufacturer and do not in any way imply a guaranteed delivery window. Many manufacturers work in a “just in time” inventory system and often take 2-20+ weeks to produce an item once an order is submitted. All deliverable items are then sent to our Japanese warehouse. Bulletproof ships a minimum of one full ocean freight container every month from Japan, oftentimes more than one a month. Ocean freight takes an average of 4 weeks. Typically it breaks down to one week in Japan for paperwork and customs, two weeks by boat and one week in US customs/clearance. Due to the wide number of variables between manufacturer and shipping schedules, delivery estimates are simply just that – estimates. We attempt to estimate conservatively and we usually deliver faster than our estimates suggest. It is not Bulletproof’s policy to guarantee delivery time of any special order item, this is impossible for us to do. By ordering you acknowledge that there is no required delivery ETA and an order may not be canceled or altered due to manufacturing or shipping delays, all ETA’s are provided as a best guess only. Please review the full Terms & Conditions here.

BP Pricing Difference

We do pricing a little differently on our JDM brands and we believe in making things simple and clear. No hidden fees or surcharges. Every price you see includes the shipping cost to our office in Los Angeles, California and all the associated taxes/duties/fees for bringing the products into the US. The only shipping you ever pay is from our facility in the US to your location. Be wary of resellers that don’t include the cost of international shipping in their pricing on JDM parts. While we believe we’ll always have the lowest all-in price on JDM products, we offer a price match guarantee for all authentic parts purchased from authorized dealers as well. For many international customers, it’s much more affordable to ship from the USA than from Japan directly, as the air freight and ocean freight costs are typically much less. However, for customers looking to ship directly from Japan outside of North America, or domestically in Japan, we can provide pricing specifically for that scenario. Please do not hesitate to contact us with any pricing questions or concerns. Please email us at sales@bulletproofautomotive.com with any inquiries.

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MMX Billet Oil Filler Cap for BMW and MINI Vehicles (with B48E / S58 engines) [MMR03-1601]

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MMX Billet Oil Filler Cap for BMW and MINI with S58 and B48E Engines

Features

Applications

Notes

Frequently Asked Questions

About MMX Performance

Reviews