P551000 Fuel/Water Separator

Donaldson fuel/water separator on Cummins lanes

Fleets standardized on Donaldson filtration often look for a fuel/water separator that tracks with Cummins ISX and X15 PM without rewriting shop habits. Donaldson supplies this spin-on fuel/water separator as an alternative in the same Cascadia, 579, and T680 conversations where Fleetguard FS1000-family numbers appear. Service targets diesel fuel and free water in the separator bowl—not crankcase oil.

Unit price is $38.50 USD before tax. Published weight is 3.0 lb. Use both when comparing against Fleetguard-branded fuel/water separator listings on the same engine family.

Follow Cummins fuel-filter guidance and your fuel-quality program for interval timing. This page adds no invented mileage targets.

Alternative does not mean optional quality checks

Technicians still verify stamp, gasket, and thread against the removed unit. Alternative catalog lines reduce brand arguments at the parts counter, not responsibility on the pad during install.

Lubricate the gasket with approved diesel-contact sealant only when the module chart calls for it, hand-start threads, and finish using the OEM tightening guidance for the mount on that VIN. Inspect for weep at idle before return to service.

ISX and X15 in three major OTR brands

Fitment summary covers Freightliner Cascadia, Peterbilt 389, and Kenworth T680 tractors with Cummins ISX or X15 engines—common owner-operator and fleet combinations. Table rows above refine years; they are not a fit contract.

Verify using filter stamp, engine serial, and VIN build data. Mid-year changes happen. We describe compatibility language only; technician confirmation on the truck is required.

Send unclear stamp photos to support@aonetruckauto.com. Walk multiple options in the fitment guide when buyers debate Donaldson versus other fuel/water separators for the same lane.

When shops choose Donaldson on Cummins power

Some terminals negotiate one filter vendor for fuel while keeping oil-filter assemblies separate. Others mix Donaldson fuel/water separators with OEM oil hardware—both patterns work when stamps match and restriction gauges support the interval.

Drain free water into a clear container during scheduled inspections. Water volume and sediment clues point to tank housekeeping or upstream contamination—not to a brand preference alone.

• Store fuel/water separator cartons away from oil-filter cartons to prevent grab errors.
• Prime the supply side after a change when the engine bulletin requires it.
• Document Donaldson install on the work order even when alternates exist in stock.

Shelf mapping for this separator

Purchase paperwork naming this Donaldson separator should be checked against the can removed from the pad. E-commerce cart and PayPal lines use the listing SKU at $38.50 each. Common crosses include FS1000 and BF1259—confirm gasket and drain layout before you treat a cross as identical.

Fuel-service habits on separator day

This spin-on sees diesel fuel and free water only. Drain water at the separator bowl per the module design. Do not treat this canister as a crankcase oil filter, and do not apply oil-filter fill habits to a fuel circuit.

Receiving and fleet returns

At 3.0 lb per unit, small PM shipments stay in parcel class for many destinations. Compare labels on delivery; dented threads warrant photos before install.

Review returns and refunds and shipping policy before bulk stocking. Opened fuel-component product may be restricted once diesel wets the media.

Payment versus mechanical sign-off

PayPal totals reflect quantity times card price with capture on success. A paid order still needs correct stamp verification before the truck leaves the bay.

Dual-vendor stock rooms

Some fleets keep Donaldson fuel/water separators on one shelf and another brand on oil-filter assemblies. Color tags and stamp logs prevent a night-shift grab error when both cartons look similar in dim light.

Contamination paperwork

When injectors or transfer pumps complain after wet fuel, fix the tank and supplier source before debating filter brand. Donaldson separators still load faster if free water and rust keep arriving from the saddle tanks.

Owner-operator buying pattern

Single-truck buyers often order one fuel/water separator with other PM parts. Confirm the stamp against the last change sticker inside the hood before checkout—Cascadia repowers are common in the used market.

PayPal line clarity

Checkout totals multiply $38.50 by quantity for this Donaldson fuel/water separator listing. Capture success confirms payment; stamp verification still happens in the bay before dispatch.

Oil-filter PM on the same ticket

If the truck also needs crankcase oil filters, complete oil service separately from this fuel separator change. Mixed tickets cause mixed procedures when shifts hand off mid-job.

Cross-dock receiving

Donaldson cartons sometimes arrive in mixed pallets from regional hubs. Scan the label against the pick line before you stage PM totes for weekend lane departures and note any crush damage on the threads.

Donaldson shelf tags in mixed brands

When Donaldson fuel/water separators share a wall with Fleetguard oil cans, use shelf tags that spell fuel versus oil. Grab errors at 2 a.m. are how dry-start high-pressure pumps happen.

Drain photos during analysis month belong in the fuel file with the Donaldson stamp visible so warranty conversations have evidence.

Before you pay, skim the shipping policy and returns and refunds. Parts questions go to support@aonetruckauto.com.

Operator: HEAVY TRUCK PARTS, INC. We are not affiliated with the truck or filter brands named on this page.