Caterpillar 528-7222 Air Filter (320D2, 320E, D6K2)

Primary Means Outer — and the Safety Element Is a Second Part

528-7222 is the outer element: the pleated cylinder you lift out when the air cleaner lid comes off. Behind it sits the secondary element, often called the safety element, and it is a different part number with a different job. The primary does the filtering; the secondary is there to keep dust out of the engine during the moment the primary is out of the housing, and in case the primary ever splits. On a machine working in quarry or demolition dust that is not a theoretical risk.

That means the routine order is two elements, not one, and the second number is the one most buyers forget. Cat's own filters guidance is blunt about the handling: the secondary element should never be cleaned, and should be replaced every third primary element change or as required. Cleaning it — blowing it out with compressed air — pushes the retained dust through the media and is worse than leaving it alone. In WIX's catalogue the outer equivalent for 528-7222 is WA11720 and the paired inner is WA11721, so those are the two numbers to quote together if you buy on cross references.

The Housing Decides, Not the Badge

Two machines with 320 on the side panel can share almost nothing in the air cleaner. Cat's parts store lists 528-7222 for the 320D2, 320D2 GC, 320D2 L, 320E and 320F L, and lists the non-round primary element 479-8989 with the 479-8991 secondary for the later 320, 320 GC, 320 GX, 323 GC and 326 GC generation. Same model number on the decal, two different elements, no interchange. Confirm by the prefix or the element, never by the model name.

Cat's own documentation even splits the decision inside a single model. The D6N dozer parts reference guide marks 528-7222 as the primary element for the circular-shaped air cleaner housing and lists 539-6920 for the square-shaped housing. If your machine is a D6N or D6K2, the shape of the air cleaner body — not the year, not the hour meter — tells you which of the two you need. Send a photo of the housing and we will match it in a minute.

What We Do Not Publish

Three deliberate omissions. There is no single diameter presented as fact, because Cat's published field values and the independent catalogues that measure the element do not agree to the millimetre — so the range is here and the confirmation happens on your side with a tape measure or a photo. There is no operating-hour interval, because Cat sets air filter servicing per machine, serial range and duty cycle, and the dustier the site the shorter the honest answer. And there is no claim that this element fits "all 320s", because Cat's own data shows that it does not.

What we do instead is the cheap part: send the number stamped on the air cleaner group, or a photo of the old element next to a tape measure, and we confirm the primary and the secondary for your machine, quote both, and dispatch in 3–7 days — FOB Shanghai or CIF to your port.

FAQ

Q: What is Cat 528-7222 and which machines does it fit?
A: 528-7222 is a primary (outer) engine air filter element cross-referenced to Caterpillar OEM 528-7222. Cat's parts store lists it for the 320D2, 320D2 GC, 320D2 L, 320E, 320E L, 320E LN, 320E LRR, 320E RR, 320F L, 323D2, 323D2 L, 323E L, 323E LN, 323E SA, 323F, 323F L and 538 excavators, the MH3022, MH3024 and MH3026 material handlers, the 527 track skidder, the PL61 pipelayer, 953, 953K, 963 and 963K track loaders, D4, D5R2, D6K, D6K2, D6N dozers, and the 120 GC motor grader. It fits the circular-shaped air cleaner housing - machines with the square-shaped housing take a different primary number.

Q: Is 528-7222 the outer filter or the inner safety element?
A: It is the outer element, the one you lift out when the air cleaner is opened. The secondary or safety element that sits behind it carries its own part number and is a separate purchase. In WIX's catalogue the outer equivalent is WA11720 and the inner listed against it is WA11721, so those two numbers are quoted together. Cat's own filters guidance says the secondary element should never be cleaned and should be replaced every third primary element change or as required.

Q: What are the dimensions of Cat 528-7222?
A: Cat's parts store publishes 8.457 in (214.8 mm) across and 16.315 in (414.4 mm) overall depth, round, standard-efficiency media. Independent catalogues converge on about 211 to 215 mm outside diameter and 398 to 414 mm length, with inner diameter values between 117 and 137 mm depending on the source. WIX's equivalent WA11720 is published at 211.3 mm outside, 117.3 mm inside and 414 mm long. Where sources disagree we say so rather than publish one number as fact.

Q: Does 528-7222 fit every Cat 320?
A: No. Cat's own data shows why the badge is not enough. The 320D2, 320D2 GC, 320D2 L, 320E, 320F L and 323E machines are on the 528-7222 list, but the later 320, 320 GC, 320 GX, 323 GC and 326 GC generation uses the non-round primary element 479-8989 with 479-8991 as its secondary. Cat's D6N parts reference guide makes the same point inside one model: 528-7222 is listed for the circular-shaped air cleaner housing and 539-6920 for the square-shaped housing. Send the number off your air cleaner group or a photo of the old element and we confirm before dispatch.