Can I substitute grapeseed oil for sunflower oil in the Andy's Fairfield Granola recipe without compromising the taste of the granola?
Andy's Fairfield Granola recipe (from Feast and on the Nigella website) uses sunflower oil but most neutrally flavoured vegetable oils can be used. Grapeseed oil is attributed with certain health benefits which may be the reson you prefer to use it, and it has a very mild flavour so should be fine to use in the granola without affecting the taste.
You could also use corn oil, canola oil/expeller pressed rapeseed oil or groundnut/peanut oil. However stronger flavoured oils such as olive oil, cold pressed rapeseed oil, other nut oils, pumpkin seed oil and toasted sesame oil should be avoided as their flavour could come through in the granola.