Cat 320D Air Filter: Standard or UHE? The Four Numbers Explained

Published: September 26, 2026By CN Machinery

Most air filter orders we correct on a 320D are not wrong because the buyer picked the wrong size. They are wrong because the buyer picked the wrong grade: an ultra high efficiency element was sold as a standard one, or the reverse, and nobody noticed until the invoice came back with a different number on it. That confusion is built into Cat's catalogue, because the same housing position carries two element numbers that are identical to the thousandth of an inch. Here is the whole family on one page, taken from Cat's own part pages for each number.

1. Two Air Cleaners, Four Primary Elements

The 20-tonne 320 family was built with two air cleaner groups — one with a dust ejector valve, one without — and the two groups take different element sizes. Each size is sold in a standard grade and a UHE grade:

Air cleaner group	Cat's published element size	Standard grade	UHE grade	Secondary element
Large cleaner (the no-dust-valve group on the 320B–320D builds)	281.6 mm diameter × 339.2 mm long (11.087 in × 13.354 in), round, primary	6I-2501	128-2686	6I-2502 150.9 × 316.0 mm
Small cleaner (the dust-valve group)	237.0 mm diameter × 330.2 mm long (9.331 in × 13.0 in), round, primary	131-8822	134-0685	131-8821

Every dimension in that table is Cat's own published specification, not a catalogue estimate: 6I-2501 and 128-2686 both appear on parts.cat.com at Overall Width and Height 11.087 in and Overall Depth 13.354 in, and 131-8822 and 134-0685 both appear at 9.331 in and 13.0 in. The grades are also Cat's own: 6I-2501 is listed in the standard efficiency range, while 128-2686 carries Media Type UHE and the attribute line "Primary ultra high efficiency air filter. Improved contamination control holds particulates during filter change."

If you are not sure which cleaner your machine has, our guide to dust valve and no-dust-valve air cleaners covers the check, and the elements themselves tell you the answer: a 281.6 mm element will not seat in a 237 mm housing.

2. What Cat Actually Claims for UHE

Ultra high efficiency is a media grade, not a housing change. Cat's own attributes for the UHE element are short and specific, and they are the manufacturer's claims rather than our test results — we quote them as such:

Cat's published attribute (UHE primary element)	Our note
"Lasts up to six times longer than standard filters"	Applies to the UHE grade. It is a claim about life in contaminated duty, not a guarantee for any particular site
"Extremely effective in fine dust and soot"	The duty that matters in crushing, quarry and demolition work — and the reason most 320D fleets in Africa and the Middle East ask about UHE at all
"Less restriction and higher air flow allows the engine to breathe better"	UHE media is not simply a denser paper element; Cat presents it as lower restriction at the same filtration duty
Description: filtration surface extends filter life "up to six times that of standard filters"	The same claim appears in Cat's product copy for the UHE element

Two things follow, and both are practical. First, UHE is worth discussing on machines that run in fine dust and soot, where the primary element is usually the part that sets the service interval. Second, it is not automatically the right answer: a UHE element costs more than the standard one, and a site that changes elements on a fixed calendar and never reaches the element's capacity is paying for life it does not use. We quote both grades and let the customer pick rather than pushing the dearer one.

3. Identical Sizes, Different Fitment Lists

This is where a wrong order becomes an argument with the dealer. Cat's compatible-model list for the standard number is not the list for the UHE number, even in the same envelope:

Number	What Cat's own list covers (visible entries)	Not on the list
6I-2501 281.6 mm, standard	320B, 320B N / L, 320C, 320D family, 320D2, 320D3, 322B, 322C, 323D family, 325B family, 966F / 966F II / 950B–950F II / 938F–938G loaders, D5N–D7R tractors, industrial engines 3116 / 3126 / 3304 / 3306 / 3406C / 3208 and gensets including G3306	—
128-2686 281.6 mm, UHE	320D, 320D L / LN / FM, 320D2, 320D2 L / FM, 320D3, 322B L / LN, 322C / 322C FM, 323D, 323D L / LN / S / SA, 323D2, 323D2 L, 323D3, 325B L / LN, loaders 950B / 950E / 950F II / 950G / 962G / 938G, D6G2 XL and LGP, IT38G / IT62G	320B and 320C
131-8822 237 mm, standard	320B, 320C, 320D, 320D2, 320D3, 320E, 320F L, M325B wheeled excavator, CP-533D / CP-563D and CS-531D–CS-683E compactors (aftermarket fitment lists)	—
134-0685 237 mm, UHE	320C / 320C L / 320C FM, 320D (L, LN, RR, LRR, FM, FM RR, GC), 320D2 (L, FM, GC), 320D3 and 320D3 GC, 320E (L, LN, LRR, RR), 320F L, 321C, 321D LCR, 322C / 322C FM, 323D–323F, plus the 323D LN and 323F mobile hydraulic power units	320B

So a 320B owner asking for "the UHE upgrade" is asking for a number his machine is not listed against, and a fleet running 320B, 320C and 320D machines together should keep the grades separated by machine rather than treat one number as the universal answer. Cat also presents these lists in pages, so what any single page shows is the visible subset; the parts book for the serial number is the only complete answer. Send us the serial and we read it rather than guess.

4. Why a Cross Number Cannot Tell You the Grade

The single most useful thing in this article. Aftermarket catalogues publish the same references against both grades in each envelope, because those references describe the physical envelope:

Envelope	Cross numbers published for both grades
281.6 × 339.2 mm (6I-2501 and 128-2686)	Donaldson P532501, Fleetguard AF25125M, Baldwin RS3504 — with the wider catalogue family running Carquest 88479, FIL HP2501, Fleetguard AF27916, Hastings AF2200, Hengst E591L, Luber-Finer LAF4501MXM, Mann C29840, Sakura A5549 / A5549M, Mecafilter FA3252, Tecfil ARS2501 and others
237.0 × 330.2 mm (131-8822 and 134-0685)	Donaldson P536457, Fleetguard AF25589, Baldwin RS3736 — with Carquest 88701, Hastings AF2290, HIFI-FILTER SA160106 and Luber-Finer LAF8145MXM on the same family lists

So when a supplier quotes "Donaldson P532501 equivalent" for a 320D, he has told you the size and nothing about the media. If your site depends on element life, order by Cat number and state the grade — 128-2686 or 134-0685 for UHE, 6I-2501 or 131-8822 for standard — and ask for the number to appear on the invoice and packing list. Cross numbers are a search lead, not a verification: match the seal diameter and the overall length against the element you removed before you buy a pallet of them.

5. The Five-Minute Check Before You Order

Pull the old primary element and measure three things: outside diameter, overall length, and the height of the seal lip. 281.6 mm against 237 mm is a difference you can see against a tape measure without any reference to a catalogue, and it tells you which air cleaner group you have — and therefore which pair of numbers applies. Photograph the element next to the tape and the number stamped on the end cap. That photograph is worth more than any cross reference when the machine has been through a rebuild, which is common on used 320-family machines that arrive with parts from two different build generations.

Then check the housing: the dust ejector valve on a dust-valve cleaner must be clear, because the ejector is what removes the bulk of the dirt before it reaches the element. A blocked ejector moves that load onto the primary and shortens its life no matter which grade you fitted. When you fit the new element, clean and inspect the seal face and confirm the latches close — a radial-seal element that does not seat lets dust straight into the intake duct and leaves no evidence on the element itself.

6. What We Do Not Publish

No price and no service interval. Both depend on facts we cannot see: the quantity, whether you take the primary alone or the primary with its secondary element, the shipping lane, and the dust load at your site. We also do not publish a filtration efficiency percentage for either grade — Cat does not state one on these part pages, and a number invented here would be worse than no number at all. What we do publish is checkable: the part numbers, the published dimensions, Cat's own grade wording, and the cross-reference families with the warning that they do not identify the grade. Send the machine model with serial prefix, the numbers off the old elements and their measurements, and we confirm both positions, quote standard and UHE side by side, and ship in 3–7 days FOB Shanghai or CIF to your port.

FAQ

Q: How many air filter numbers does a Cat 320D have?
A: Four primary element numbers, because the 320D was built with two different air cleaner groups and each group is sold in two efficiency grades. The 281.6 mm envelope takes 6I-2501 (standard) or 128-2686 (UHE); the 237 mm envelope takes 131-8822 (standard) or 134-0685 (UHE). Each group also has its own secondary element: 6I-2502 for the 281.6 mm cleaner and 131-8821 for the 237 mm cleaner. Measure the old element before ordering.

Q: Can I upgrade a 320D from the standard element to UHE?
A: The UHE element fits the same housing position and Cat publishes identical dimensions for the two grades in each envelope, so the physical fit is the same. What changes is the Cat number, the media grade and the price, and Cat's own compatible-model lists for the two numbers are not identical — 128-2686 does not list the 320B or 320C that appear on the 6I-2501 list, and 134-0685 does not list the 320B that appears on 131-8822 fitment lists. Send the machine model and serial and we will confirm the grade for your build against the parts book.

Q: Does a Donaldson or Fleetguard cross number tell me if the filter is standard or UHE?
A: No, and this is the most expensive misunderstanding in this family. Aftermarket catalogues publish the same references against both grades: Donaldson P532501, Fleetguard AF25125M and Baldwin RS3504 appear for 6I-2501 and 128-2686 alike, and Donaldson P536457, Fleetguard AF25589 and Baldwin RS3736 appear for both 131-8822 and 134-0685. A cross number identifies the envelope, not the media grade. If the grade matters, order by the Cat number.

Q: What does Cat claim for the ultra high efficiency element?
A: On its own part pages Cat states the attribute lines for the UHE element as "Lasts up to six times longer than standard filters", "Extremely effective in fine dust and soot" and "Less restriction and higher air flow allows the engine to breathe better", and describes the primary UHE element as improving contamination control by holding particulates during a filter change. Those are Cat's published claims for the grade; we quote them as the manufacturer's figures and do not present them as our own test results.