Hi,

Bottle density method.

Cheapest yet accurate are capillary type (Ubbelohde) viscometers. To work with it you only need a decent isothermal bath and a stopwatch.

Anusha, Tibor is right: Ubbelohde viscometer is accurate and cheap. Another option, maybe not so accurate, but very easy to use (since you have a good thermal control) are Flow cups: Ford, ISO, DIN, ASTM... A stopwatch is also necessary.

Another option to analyze the viscosity of your fluid could be the Falling ball method. Especially for low to medium viscous fluids it is accurate and potenially easier to clean as the Ubbelhode, because the glass of the Ubbelhode is quite thin and breaks easily. Even when Ubbelhode is the most accurate esp. for very low viscous fluids.