Graphite vs. MLS: What's the Difference in Gasket Materials?CUMMINS CYLINDER HEAD GASKET | Highway and Heavy Parts

When it comes to gaskets, the material can make all the difference. Most current gaskets are made of a combination of metal and a composite material like graphite or asbestos, although asbestos has been losing popularity due to safety concerns (HHP only sells asbestos-free gaskets!). In recent years, though, a newer type of gasket has been developed to meet the increased demands modern engines place on them. These multi-layer steel (MLS) gaskets, while not standard on all engine models yet, have been growing in popularity, due in part to their better handling of increased temperatures. But they come with their own set of issues that aren't shared by graphite gaskets.


So What's the Material Difference?

Graphite Gaskets

As we mentioned, graphite gaskets and other composite type gaskets consist of a metal core with each side covered with the composite material. Some newer gaskets have multiple layers of metal and include a rubber-like substance, but that depends on the manufacturer. The graphite seals well on even an uneven surface and more readily allows for movement between components due to its softer nature.

MLS Gaskets

These gaskets, as the name implies, are made up of layers of embossed steel with a thin outer coating to help with sealing. While they can tolerate higher operating temperature much more efficiently, they aren't nearly as forgiving as the more compressible graphite material, so the mounting surface must be as smooth as possible to prevent leaks.

Either way, there may be times you need to replace your head gasket. If you're looking for a replacement but aren't sure where to start, take a look at our previous blog, Selecting Head Gasket Sets, for more information.


So Why Choose?

There are definite perks to each type of gasket material. Graphite, for example, is often less expensive than an MLS gasket, and due to their newness and unforgiving nature, it could be difficult to retrofit an engine to accommodate an MLS gasket. Similarly, graphite is much more forgiving, and can seal on a rougher surface due to the ease with which they can be compressed. They also don't generally require any additional sealants. (In fact, applying sealants can create more problems for you). Because of its more slippery nature, graphite works well between components of different materials (an iron block and aluminum head, for example), allowing for a sliding motion to occur during operation, as well as better adjusting to the different rates at which the metals expand.

Rising out of the demand for engines to perform under higher and higher pressure, MLS gaskets are better with withstanding heat than a more traditional gasket. MLS gaskets are much less likely to blow, due to an increased tolerance for cylinder pressure, keeping them operational past when a graphite gasket might fail. An MLS gasket requires as close to absolute smoothness as possible, as it will not compress down in the same way a composite gasket might to fill small areas of roughness. These areas could then lead to potential leaks and further engine trouble.

MLS gaskets are newer, and therefore not available on all engine models. According to some, if your engine comes with an MLS gasket, it should be replaced with an MLS, to avoid issues.


If you're looking for new gaskets, you're engine make can be a huge factor into what kind you end up getting. As always, we recommend shopping with your engine serial number handy to help you find the perfect fit for your engine.

We carry a large selection of gaskets and gasket sets to help you with your next diesel engine job.

Or, if you're not sure what you need, let us help! Request a quote online or call one of our certified techs at 844-304-7688 for more information.