Environmental factors such as poor fuel quality, hot weather and stop-start driving conditions can lead to sludge, varnish and carbon build-up in your engine: three factors that reduce engine life, power and fuel economy. Castrol Ultraclean is a synthetic blend engine oil available in 0W-20, 5W-20 and 5W-30 grades. Its double-action formula has been proven to clean away the sludge that can block engine oilways (when tested in engines with a high level of sludge) and helps prevent new sludge formation thanks to its synthetic technology. In fact, it provides up to 1.4X better sludge protection than is demanded by the latest industry standard. If keeping your engine clean is important to you, it's good to know that no other oil keeps engines cleaner.