Why does it matter?
There are many different styles, designs and colors of Mugen oil caps that are currently available for sale. Genuine Mugen oil caps are made with the best materials available and finished in color coatings that will not fade as quickly as fakes. Genuine Mugen oil caps also use a specifically-engineered, flat, grooved rubber seal for proper fit and oil containment designed for the heat generated by your motor.
How do I spot fakes?
1. Genuine Mugen oil caps will have a flat, ridged rubber seal around the threads. Fakes have a rounded seal that resemble a common o-ring. The picture below shows a genuine oil cap with the flat, grooved rubber seal.
2. New, genuine Mugen oil caps ship with the self-adhesive center Mugen badge held in place with a small piece of clear tape. Mugen ships this way so owners can control the rotation of the circular badge upon installation. Oil caps with the Mugen badge pre-installed will not have a properly rotated Mugen logo upon installation.
3. Price seems too low to be true, or ships from a locale or seller that is not known to carry genuine items.
4. Mugen part number is missing from the package. Fakes can include elaborately copied packages that include the clear folded box, printed cardboard and black display foam.
5. Seller has many oil caps for sale, but this is one of the only Mugen products they sell. Beware of sellers that only sell some combination of reservoir covers, pedals, oil caps, shift knobs and radiator caps -- the most commonly produced fakes.
How do I buy genuine?
Obviously we recommend that you to buy from King Motorsports, where you can rest assured that your Mugen products are genuine and made with the correct materials and quality control that Mugen intended. If you are buying an item second hard, follow the same caution you would with any other purchase. Ask to see photos of packaging, if they have it. Ask if they have an original invoice -- many private sellers of second-hand items within the USA often have boxes (applies to larger parts boxed up in cardboard with original Mugen stickers) and invoices that are printed with KING MOTORSPORTS on them.
http://www.kingmotorsports.com/advsearch.aspx?SearchTerm=mugen+oil+cap