Here is a letter from Fram trying to defend there use of cardboard end caps instead of metal. I have seen so many cut open at a friends machine shop with the cardboard ends blown off.
A Letter from Fram
Thank you for the e-mail regarding the construction and micron rating of Fram oil filters. We welcome the opportunity to be of service.
Fram filters meet the requirements of the original equipment filter designed for a specific engine. Our filter applications follow the recommendations of the vehicle manufacturer for form, fit, and function. Fram filters follow internally targeted design guidelines to meet the functional requirements of a given filter. Fram filters are tested against SAE standards to ensure uniform product quality and performance. Material construction will vary between filter manufacturers. We believe Fram filters have a proven record for providing reliability, superior quality, and engine protection over the service life of the filter.
A common misunderstanding among our customers concerns the end disks in the oil filter. These disks hold the glue which keeps the pleated media formed into a rigid circular tube. The glue-to-media interface is also one of the sealing surfaces keeping dirty and filtered oil from mixing. One common myth is that only metal end disks can adequately seal and have enough strength in the hot oil environment. For this reason, Fram filters are criticized for having cardboard end disks. The issue is, the material doing the sealing is the adhesive, regardless of the material of the end disk. What matters is the strength of the adhesive, its proper curing, the thoroughness with which it can be applied to the disk, and its adhesion to the disk. By using cardboard end disks, Fram filter engineers are able to specify adhesives with excellent strength and sealing properties, and strong adhesion to the disk (intuitively, it is easy to make a strong glue bond with cardboard). Moreover, just as paper media itself is able to withstand the hot oil environment, so too is the end disk designed of fibers engineered to be strong and inert in hot oil. The thickness and strength of the adhesive also stiffens the end disk considerably.
Fram engineers perform hot oil circulation tests on the filter element and also regularly cut open used filters to examine how well they have withstood the rigors of actual use on a vehicle. For over 38 years, Fram end disks have stood up to hot oil and their adhesives have sealed off the dirty oil.
Fram's latest entry in the automotive oil filter market is the X2 Extended Guard oil filter. The Fram X2 Extended Guard filter uses a filter media that includes a reinforced mesh screen for maximum pleat integrity, durability, and oil flow. The inclusion of the metal screen increased the glue tolerances or thickness required for proper adhesion to the end disk. The original X2 prototype development specified the cardboard end disk technology. However, the increased amount of adhesive required to join the cardboard end disk to the screened media resulted in prototypes that did not conform to design standards. We had no choice but to use a steel end disk with the X2 filter media to provide uniform Extended Guard oil filter construction.
Fram automotive oil filters, including the standard Extra Guard and premium X2 Extended Guard filters, have a micron rating of 10 micron.
If you require further assistance with Fram filter construction, please contact the Fram Engineering Department directly at 1-419-661-6700.
Thank you for your interest in Fram filters.
Cordially, Scott Jacobs, Catalog/Technical Service Representative