Hazmat, and hauling diesel fuel?

Any quantity of 119 gallons or more must be placarded. Diesel does not require one.
What Hazardous Materials require a Hazardous Materials Safety Permit?

 

Op is asking about needing the "Federal Hazardous Materials Safety Permit". Not whether he would need placards or whether diesel is considered hazmat. FMCSA regs:

What Hazardous Materials require a Hazardous Materials Safety Permit?

The following hazardous materials carried in these quantity amounts will require an HM Safety Permit:

• Radioactive Materials: A highway route-controlled quantity of Class 7 material, as defined in 173.403 of 49 CFR.
• Explosives: More than 25kg (55 pounds) of a Division 1.1, 1.2 or 1.3 material, or an amount of a Division 1.5 material requiring a placard under Part 172 Subpart F of 49 CFR.
• Toxic by Inhalation Materials:
  • Hazard Zone A: More that one liter (1.08 quarts) per package of a "material poisonous by inhalation," as defined in 171.8 of 49 CFR, that meets the criteria for "hazard zone A," as specified in 173.116(a) or 173.133(a) of 49 CFR
  • Hazard Zone B: A "material poisonous by inhalation," as defined in 171.8 of this title, that meets the criteria for "hazard zone B," as specified in 173.116(a) or 173.133(a) of 49 CFR in a bulk packaging (capacity greater than 450 L [119 gallons])
  • Hazard Zone C & D: A "material poisonous by inhalation," as defined in 171.8 of this title, that meets the criteria for "hazard zone C," or "hazard zone D," as specified in 173.116(a) of this title, in a packaging having a capacity equal to or greater than 13,248 L (3,500 gallons)
    • Due to Anhydrous Ammonia (ammonia, anhydrous) having both international and domestic entries in the Hazardous Materials Table (HMT)(See 49 CFR § 172.101), considerations must be made in order to determine the need for a Hazardous Materials Safety Permit (HMSP):
      • For Anhydrous Ammonia in “domestic transportation” (See 49 CFR § 171.8) and described as UN1005 ammonia, anhydrous 2.2 Inhalation Hazard, an HMSP is not required.
      • For Anhydrous Ammonia described as UN1005, ammonia, anhydrous 2.3 Poison Inhalation Hazard or Toxic Inhalation Hazard, Zone D, and when transported in a packaging having a capacity greater than 13,248 L (3,500 gallons), an HMSP is required. In these instances, Anhydrous Ammonia meets the definition of a Material that is Poison-By-Inhalation or Toxic-By-Inhalation as defined in 49 CFR § 171.8 and meets the criteria for a hazard zone D as specified in 49 CFR § 173.116(a).
• Methane: A shipment of compressed or refrigerated liquefied methane or liquefied natural gas or other liquefied gas with a methane content of at least 85% in a bulk packaging having a capacity equal to or greater than 13,248 L (3,500 gallons) for liquids or gases.

 

Volume trumps the weight with liquids, and 119 gallons or more in 1 container also requires a tank endorsement, IIRC.

 

1001 lbs is when a non-ID placard is required for a given class of table 2 you may have on board.