Volkswagen installed plastic sleeves over some of the fuel lines that run through the engine compartment, and there has always been some speculation as to why. Our analysis is that it is for abrasion protection ONLY. These sleeves were constructed of plastic, so heat clearly wasn't a design consideration.
Fuel line antiabrasion sleeve kit – GoWesty
Fuel Line Sleeve 3/8 compression style seal - 5 pack - BT-Power SK99038
Bus - GoWesty Innovations
PET High Anti-abrasion Sleeving
PET High Anti-abrasion Sleeving
Fuel Line Anti-Abrasion Sleeve Kit – GoWesty
Vanagon - GoWesty Innovations – Page 10
Gaine anti-abrasion en polyester tressé (2.1m) - AFS - Application Fast Set
Fire Sleeve made in Britain, Hydraulic Hose Abrasion Sleeve, Firejacket, Pyrosleeve, Protective Sleeving Manufacturer Online, uk
84 Vanagon BroadStreet Automotive Invoice, PDF, Suspension (Vehicle)
Fuel filler hose syncro – GoWesty
Heavy Duty T-Shirt - Long Sleeve Logo Red L
Shop StarTech.com 1.5m (4.9ft) Cable Management Sleeve - Spiral - 1 (25mm) Diameter - W/ Cable Loading Tool - Black (CMSCOILED) - cable sleeving kit