There are several threads in this forum on possible ways to make an engine warm-up faster, so this paper may be of interest (free download). It uses heat from the exhaust gas recirculation (EGR) line to heat the engine oil.
Burke, R., Brace, C., Cox, A., Lewis, A., Hawley, J. G., Pegg, I. and Stark, R. (2011). Systems approach to the improvement of engine warm-up behaviour. Proc. of Inst. Mech Engrs, Part D: Journal of Automobile Engineering, 225 (2). pp. 190-205. ISSN 0954-4070
http://core.ac.uk/download/pdf/2809022.pdf