Experimental results are presented for a compression ignition engine with one cylinder refrigerated by air, fueled with soy straight vegetable oil (SVO), filtered at 500 nm and blended with diesel at volume percentages of 10, 30, 50, 70 and 100%. Performance tests varying the injection angle and the fuel temperature were conducted. The results show an increase in torque and power compared to pure diesel, especially with the SVO50 and SVO70 mixtures. However, there was an increase in the specific consumption, although engine efficiency was only slightly lower due to the lower heating value of oil. The use of SVO as fuel is feasible, but durability tests must be performed, mainly to discover potential maintenance problems. (C) 2011 Elsevier Ltd. All rights reserved.