On the viscosity of Oils and Fats
Technical measures of rancidity of oil are the Free Fatty Acid and Peroxide levels; more graphic is The Fridge Test; assuming that the more viscous an oil, the less healthy, an oil, fat, or food containing same, chilled to 5 degrees C reveals itself.
a) Oily fish - particularly tuna, mackerel, salmon; the oil in the flesh remains liquid; contains Omega 3 oils. If the oils in their system were to become viscous at a polar sea temperature of 5 degrees C or less, they would be unable to swim!
b) Commercial refined vegetable oils (Sunflower, Soya, and Canola); remain liquid because they have been "winterised" .. that is, the oil has been chilled to a low temperature such that solid waxes precipitate out. Typically, FFA is <0.1% and peroxide <2.
c) Extra Virgin Olive Oil (always unwinterised), becomes cloudy.. illustrates absence of winterisation. Typically, FFA is about 0.7% and peroxide is 12. A virgin (ie first press) olive oil with an FFA of in excess of 0.8% may not be called, in terms of the International Olive Oil Council, "Extra" virgin. Other unrefined oils stocked by us which fall into this category are our cold pressed Sunflower, Avo, and Macadamia oils.
d) Palm Oil congeals. It is used by fast food chains exclusively for deep frying because it is cheaper, gives a better "mouth feel" when hot, and lasts longer without deterioration. Your chips taste terrible the morning after, because Palm Oil has a high saturated fat component (see below). Join the Slow Food Movement!
e) Cooked Red meat congeals - as it does in one's arteries.
f) Processed meat, ditto, but worse because of the trans fatty acids.
g) Cooked Lamb (congeals worst of all), The body temperature of a lamb is in excess of our temperature of 37.5 degrees. Our bodies are therefore unable to metabolise the fat.

Practical notes for deep fryers.
 

The life cycle of a batch of oil can be tracked chemically by determining the level of the Free Fatty Acids by titration, test strips, or by digital probe (we have researched these options - give us a call to discuss). A quick visual test appears below.A. Break-in. Clear appearance; little oil absorption into food, and minimal odour. Taste and texture not optimal. FFA <0.2%. B. Fresh. Browning and crisping at the edges of the food. Increased absorption by food materials. C Optimal. Golden brown, crisp, optimal absorption. FFA <0.6%. D. Degraded. Darker, edges too crisp, spots and hardening. Excessive absorption. Rancid aftertaste. FFA >0.6% E. Runaway. Hard fry surfaces, bad odour and maximum absorption. Uneven cooking. FFA <1.2%

Recommended Applications of our oils
We list below, in descending order of stability, our oils;
Grapeseed (refined); for high temperature longer duration cooking (if you can afford it!)
Peanut (refined); also stable, commonly used in stir fries/wok cooking, sometimes used for deep frying.
Sunflower and Canola (refined); the workhorses, general purpose oils.
Sunflower (Cold Pressed), Olive, Avocado, Macadamia, Pumpkin Seed; use cold on salads or directly on plate.

Click here for a link to a useful, technical article on edible oils in South Africa from the SA Journal of Clinical Nutrition
Summary
Health professionals recommend that max 30% of our total daily calories should come from fats, with a max saturated fat intake of no more than 10%, and a cholesterol intake of no more than 300 milligrams.
Canola has the best fat ratio: it is low in saturated fats (which increase LDL cholesterol levels), high in unsaturated fats (which lower LDL cholesterol levels) and, being a vegetable oil, is cholesterol-free.