Rapeseed is a
heavily bred plant (both conventional and GMO). In fact, its oil has been regarded inedible for centuries due to the presence of
erucic acid. Not until the last decades, new breeds (“canola”) have been developed, with erucic acid levels low enough for human consumption.
Manipulation of the fatty acid profile will in general alter its saponification value (that's the whole point why to use
soap calculators). This is the case for blending oils, as well as breeding of rapeseed/canola too.
With kitchen-class retail RBD canola oil, I personally have had decent success with the SAP value tabulated as “canola oil” – though I'm pretty sure that it is not the original “canola®”, but another cultivar with obviously similar fatty acid profile (Europeans' resistance against GMO profiteering has paid off). That said, canola is a somewhat troublesome ingredient due to its DOS tendency, and I'd use it sparingly for soap anyway, and then minor SAP imprecisions don't matter too much.
YMMV if you have access to raw/inedible, cosmetic-grade, industrial (biodiesel etc.) or imported rapeseed oil. If your supplier provides SAP values (you might just ask!), it's the best source. Otherwise you are left with the options of guessing SAP, measuring it (titration), or replacing canola with an oil of more consistent properties, like HO sunflower/safflower (or, if you want to up PUFAs, a blend with HL sunflower/safflower, RBO or cottonseed oil).
According to the
Soapee database,
“Rapeseed oil, unrefined canola” is at NaSAP
0.125, and
“Canola oil” (both regular and high-oleic) are at NaSAP
0.133. There you have your numbers!
Also compare the numbers of mustard oil, abyssinia oil, camelina oil, broccoli seed oil, and all the other brassicaceae, which are botanically very closely related to canola – just to get a rough idea how much fatty acid profiles can vary within that tribe of plants.