Replacement parts supplied by the manufacturer are considered original equipment, or “OE,” while non-OE parts are manufactured by aftermarket companies. Before you say, “Of course this magazine is going to recommend Subaru OE parts,” take a look at the results of an evaluation recently completed by product-development engineers at Fuji Heavy Industries.

The engineers compared OE and non-OE fenders for the same Subaru Legacy. Tests compared key points concerning manufacturing and resistance to rust.

Before you say, “Of course this magazine is going to recommend Subaru original equipment parts,” take a look at the results ...

At first glance, the OE and non-OE front fenders seem identical. In fact, they are made of the same material and have the same strength.

However, the aftermarket supplier is not working with factory tooling. When photographed under identical conditions, close scrutiny reveals subtle differences in appearance between the two. The lines where the stamping machine shaped the fender are sharper on the OE part. They’re more clearly defined than on the non-OE fender. The OE replacement fender more closely matches the vehicle’s original one.

Another difference is in the precision with which the fenders are made, particularly the placement of the attachment holes. The OE fender’s holes allow it to fit perfectly. However, the non-OE fender’s holes are out of line, which leads to the possibility of bending the fender when attaching it to the vehicle’s body. The fender will not fit correctly.

It seems logical that fenders of similar material and thickness should have the same rust-prevention capabilities. But more is involved than the thickness of the steel. Cross-sections of the fenders show a significant difference between them on the steel’s surface.

The non-OE fender has a layer of electrolytic paint about 15 microns thick as protection. (By comparison, 25.4 microns equal one-thousandth of an inch, and one millimeter equals 39.37 microns.)

On the other hand, the Subaru OE fender is galvanized with zinc (a base layer of between six and seven microns) and then coated with electrolytic paint about 30 microns thick. The non-OE fender has no galvanization.

Both the zinc and the thicker layer of electrolytic paint better protect the fender from deterioration and rust.

In addition, the zinc helps to protect the OE fender from rust due to scratches and exposure to salt and high humidity. Comparison scratch tests that reproduced the effects of one year in a snowfall region showed the durability built into the OE fender, which demonstrated far less rust than the non-OE fender. Lack of zinc around the mounting holes and along the fender’s edges made it more prone to rust.

If your vehicle is damaged, carefully consider the advantages of Genuine Subaru Replacement Sheet Metal. It’s manufactured to tighter tolerances and coated with materials that stand up better to rust and corrosion. Genuine Subaru Replacement Parts are factory-tested for accurate stamping, proper fit, and superior rust protection. They look better and last longer, saving you money in the long run.