Viton APA is an abbreviation for "Advanced Polymer Architecture" based on dramatically improving processing characteristics, including flow and cure without detriment to end use performance.

Trends in automotive powertrain applications are pushing elastomeric sealing materials to their limit, longer life expectations, longer warranties, hotter engines, more aggressive lubricants and fuels and so APA grades with peroxide curing systems are used in order to make them suitable for many of the applications.

In addition to all the grades having outstanding thermal properties :

GBL-S grades provide very good compression set resistance with improved resistance in a range of media such as aromatic hydrocarbons,alcohols,water steam and acids.

GBLT-S grades give additional resistance at lower temperatures

GF-S grades combine very good chemical resistance and compression set and a very low permeation rate.

GFLT-S grades give additional resistance at lower temperatures

GLT grades offer the lowest temperature resistance in the Viton range with a tested TR-10 retraction of -30 deg C.

ETP-S grades. There is a separate index for this particular grade. See FAQ section-Viton Extreme

All APA grades offer some steam resistance with minimal swell but GF-S grade performs very well upto 150 deg C . However resistance drops markedly at temperatures  over 150 deg C

Viton GLT offers the lowest temperature resistance within the Viton range with temperatures (subject to application) as low as -40 deg C