Almost every fuel filter query we get for a Next Gen GC excavator is really a question about a pair. The machine carries a separator element and a secondary element, they look similar on a bench, both catalogue pages list the same machines, and only one of them fits each housing. Everything below is taken from Cat's own parts pages for the two numbers, and where Cat prints two different figures for the same dimension, we say so instead of picking one.
1. Two Elements, Two Numbers, Two Jobs
Cat files the two positions in different branches of the catalogue, which is the cleanest way to see that they are not alternatives to each other:
| 523-4987 | 509-5694 | |
|---|---|---|
| Cat's part name | Element-Separator | Secondary Fuel Filter Element |
| Catalogue branch | Engine Filters > Fuel Water Separators | Engine Filters > Fuel Filters |
| Diameter (Cat) | 4.043 in — 102.7 mm | 3.484 in — 88.5 mm |
| Length (Cat) | 10.169 in — 258.3 mm (description line: 250.3 mm) | 6.654 in — 169 mm |
| Efficiency category | Ultra High Efficiency | Not stated on Cat's sheet |
| Flow direction | Out-to-In | Out-to-In |
| Filter type / material | Cartridge, polyamide plastic, Meltblown media | Cartridge, polyamide plastic, Meltblown media |
| Position in the line | Upstream, inside the water separator housing | Downstream, the fine element |
The functions are not interchangeable and neither is the hardware. The separator element is the one that has a housing with a drain; it is where water is meant to stop. The secondary element is the precision stage behind it. Cat states the relationship in its own product copy for the separator line — fuel water separators are built to extend the life of the secondary filter and precision fuel system components — and Cat's fuel water separator literature puts the separator's job in numbers: removal of more than 98% of debris 10 microns and larger, and virtual elimination of free water. Water in diesel is not a filter problem you can postpone: it breaks the film strength that keeps injector plungers from scuffing their barrels, and injectors cost many times what the element does.
2. Why the Two Numbers Get Confused
Three reasons, all visible on parts.cat.com. First, both pages sit under Engine Filters, so a search for "320 GC fuel filter" returns both numbers. Second, both pages carry the same C4.4 compatible-model list, so a buyer checking fitment sees the model he owns on both pages and stops reading. Third, the description block on the 509-5694 page uses the fuel water separator wording, while the part title on the same page says Secondary Fuel Filter Element and the specification sheet says cartridge, out-to-in, 88.5 mm × 169 mm. When Cat's copy and Cat's spec sheet disagree, the spec sheet and the dimensions are what you order against.
The bench test takes ten seconds: measure the diameter. An 88.5 mm element will not seal in a housing machined for a 102.7 mm element, and 169 mm against 258.3 mm is visible against a tape measure without opening a catalogue.
3. The Machine Lists Are a C4.4 List — and They Are Not Identical
Both elements are listed across the same engine platform, not against a single model, which is good news for a fleet running mixed sizes:
| Machine family | Models (Cat's compatible-model lists) |
|---|---|
| Excavators | 320, 320 GC, 320 GX, 323, 323 GC, 323 GX, 325, 326, 326 GC, 330, 330 GC, 333, 333 GC, 335, 336, 336 GC — the separator list adds 316 GC, 340, 345, 345 GC and 350 |
| Forestry excavators | FM538, FM548, FM558 — the separator list adds FM568 |
| Wheeled excavators | M314, M315, M315 GC, M316, M317, M318, M320, M320 GC, M322, MH3026, MH3040 |
| Wheel loaders | 926, 930, 938, 950, 962 |
| Motor graders | 120 GC, 140, 140 GC |
| Material handlers | MH3022, MH3024, MH3032, MH3040 — the separator list adds MH3050 and MH3250 |
| Mobile hydraulic power units | 330 MHPU — the separator list adds 336MHPU and 340MHPU |
| Forestry | 538, 548, 558, FM528, FM528 LL — the separator list adds 568 |
| Industrial engine | C4.4 |
So for a 320 GC, 323 GC or 326 GC on the standard C4.4 build, the answer is simply: both numbers. The place that trips people is a fleet that also runs a 350 or a 316 GC — those machines appear on the separator list, so "order the fuel filter pair for every Cat we own" produces an element that has no matching second position. Read the parts book per machine, or send us the model and we will read it for you.
4. What Else Sits on the Same Service
Cat's own "frequently bought together" block on both pages is a fair description of a full service on these machines, and it is a useful checklist when you are consolidating a shipment: the fuel pair (523-4987 with 509-5694), the engine oil filter element 322-3155, the engine air pair 479-8989 primary with 479-8991 secondary, and a cabin air filter — Cat lists 500-0957 and 580-5439 against these machines, so check which one your cab takes before ordering. Cat also sells these as maintenance kits grouped at 250, 500 and 1,000-hour intervals by equipment type, which is the right place to take the interval number from rather than from a website.
5. The Figure Cat Prints Two Ways
Before you order the separator element, look at the length. Cat's specification sheet for 523-4987 gives Length 10.169 in, which is 258.3 mm. The attribute line in the description block on the same page gives 250.3 mm (9.85 in). Both are live on parts.cat.com today, and 8 mm on a cartridge that has to seat and seal is not a rounding detail. We quote both figures and ask for the measurement of the element coming out. If two suppliers are offering you a 250 mm element and a 258 mm element at different prices, they are not necessarily both wrong — measure yours and the argument is over.
6. What We Do Not Publish
No price: quantity, lane, and whether you take the pair or the whole service set decide it. No hour interval: Cat publishes interval-based maintenance kits per equipment type, and we will not convert that into a number for a machine we have not seen or a fuel quality we cannot check. No cross-reference for the separator element: for 509-5694 we could verify two catalogue numbers from independent sources (HIFI SN40859, SF-FILTER SK48942), but for 523-4987 every listing we found was a supplier code rather than a catalogue cross, so we publish none and verify the element against its dimensions instead. And no claim that a catalogue cross number is a fitment guarantee — cross lists are leads; the diameter and length are the evidence. Send the model with serial prefix, the numbers stamped on the old elements and their measurements, and we confirm both positions, quote the pair with seals, and ship in 3–7 days FOB Shanghai or CIF to your port.
FAQ
Q: What is the fuel filter part number for a Cat 320 GC?
A: A 320 GC takes two fuel elements, not one. The separator element is 523-4987 (Element-Separator, Ultra High Efficiency, 4.043 in / 102.7 mm diameter, 10.169 in / 258.3 mm length) and the secondary fuel filter element is 509-5694 (3.484 in / 88.5 mm diameter, 6.654 in / 169 mm length). Both are cartridges with out-to-in flow. The same pair is listed for the 323 GC, 326 GC, 330 GC and the rest of the C4.4 Next Gen family.
Q: Do the 320 GC, 323 GC and 326 GC use the same fuel filters?
A: Yes — they appear on the same Cat compatible-model lists for both 523-4987 and 509-5694. Those lists are built on the C4.4 platform rather than on one machine, and they also cover the 320, 320 GX, 323, 323 GX, 325, 326, 330, 333, 335 and 336 GC, the M314 to M322 wheeled excavators, the 926 to 962 wheel loaders and the 120 GC / 140 motor graders. The lists for the two numbers are not identical, though: 523-4987 also covers the 316 GC and the 340, 345, 345 GC and 350 excavators.
Q: Can I fit the separator element 523-4987 in place of 509-5694?
A: No. They are different sizes in different positions. Cat publishes 523-4987 at 4.043 in (102.7 mm) diameter and 10.169 in (258.3 mm) length, and 509-5694 at 3.484 in (88.5 mm) diameter and 6.654 in (169 mm) length. The separator sits upstream in the water separator housing and the secondary element sits downstream, which is the order Cat describes when it says fuel water separators are built to extend the life of the secondary filter.
Q: Why does Cat print two different lengths for 523-4987?
A: Because the same page carries both. The specification sheet on parts.cat.com gives Length 10.169 in, which is 258.3 mm; the attribute line in the description block gives 250.3 mm (9.85 in). We publish both rather than choose, and ask for the measurement of the element being replaced. The diameter is not in dispute at 4.043 in (102.7 mm).
Need the Fuel Pair for a 320 GC, 323 GC or 326 GC?
Send the machine model and serial, and the numbers or measurements from the old elements. We confirm the separator 523-4987 with the secondary element 509-5694, add the oil and air elements for the full service set, and ship on one order.
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