Generac — Testing DEF
Maintenance · DEF system
From a Generac owner's manual covering: MDG150, MDG175, MDG250. Check it applies to your exact model before use.
Applies to: Generac MDG150, Generac MDG175, Generac MDG250
Before you start
- Do not create DEF by mixing agricultural grade urea with water.
Procedure
- Draw a DEF sample into a clear container; DEF must be crystal clear.
- If cloudy or tinted, drain tank, flush with distilled water, fill with new DEF.
- If it passes visual and smell tests, check concentration with a refractometer.
- Correct concentration is 31.8–33.2% urea.
- If out of specification, drain, flush with distilled water, and fill with new or good DEF.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 31.8–33.2% urea
- ISO 22241-1
Full service-parts list: Generac MDG150 →, Generac MDG175 →, Generac MDG250 →
Source: Generac owner's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.