Set the testing schedule from the generator manufacturer requirements, fuel storage conditions, operating needs and site maintenance plan. The supplied kit documents do not establish a universal annual interval or mandatory test panel for every Gulf installation.

Use W-5 for a compatible-fuel water check, FCT-100 for diesel/heating-oil clarity and water, and DS-1 for diesel bacteria and mold. Use appropriate laboratory analysis when precise measurements or formal fuel acceptance are required.

Water in stored diesel is an important part of a contamination investigation. A water or clarity check helps identify what needs attention, while DS-1 checks for bacterial and mold growth. Investigate the source of water and the storage conditions rather than assuming every Gulf tank has the same contamination rate.

A positive DS-1 result is a reason to investigate water first. Dieselcraft advises finding and removing water, then assessing fuel polishing before deciding on treatment. Do not treat a positive slide as an automatic instruction to add biocide; follow the product instructions and the applicable site procedures.

DS-1 uses a two-sided slide to screen a diesel sample for bacterial and mold growth. Read bacterial growth at 24–36 hours and mold at 36–48 hours using the supplied instructions. Each kit supplies one single-use slide for one sample; do not reuse it. A negative reading means no growth was detected under the test conditions, not complete fuel certification.

Start with the visual clarity stage. If visible free water is present, the sample has failed: stop and skip Test 2. Otherwise follow the manufacturer clarity instructions: a clear view of marks #1 and #2 indicates PASS; haze obscuring #3, #4 or #5 indicates FAIL.

For the water stage, use the supplied capsule and the FCT-100 instructions. Let the powder settle before interpreting its colour. This is a general field indicator, not a precise laboratory water measurement or a universal fuel-acceptance limit.

W-5 checks for detectable free and suspended water in compatible fuels through a qualitative colour reaction. Follow the W-5 instructions for the selected container and fuel type; pink indicates a water-related failure under the test conditions. Do not interpret it as an exact ppm reading, dissolved-water measurement, or proof of zero water when white. Fuel-blend sensitivity varies. The kit supplies five capsules for up to five single-use water checks.

Choose W-5 for a rapid water check in gasoline, diesel or biodiesel blends; FCT-100 for clarity and water on a diesel or heating-oil sample; and DS-1 for bacteria and mold in diesel. Count sample locations and retests separately. See the selection section above and the Technical Hub guide for sampling and result interpretation.

The supplied FCT-100 instructions specify diesel fuel and heating oil. W-5 includes gasoline, diesel and biodiesel blends; DS-1 is for diesel only. Do not transfer fuel compatibility from one model to another.

Follow the sampling instructions for the selected kit. DS-1 and FCT-100 recommend bottom-of-tank sampling when possible; W-5 allows checks at multiple locations. Label each sample with its source, date and purpose. A result represents the sample tested, so separate locations and later retests need their own sampling and reagent allocation.

No. The supplied test-kit documents do not establish a universal acceptance limit for every engine or installation. Use the applicable equipment requirements and an appropriate analytical method for precise water concentration, particle size or formal fuel acceptance. A field PASS answers the selected check, not every aspect of fuel quality.

Do not reuse a DS-1 slide. Follow the disposal guidance in the official DS-1 PDF and the applicable site waste-handling procedures. Do not use a generic household disposal method in place of those instructions.