Question: is castrol gtx ultraclean semi synthetic?
Answer: No Oil Keeps Engines Cleaner Castrol® GTX® 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 and helps prevent new sludge formation thanks to its synthetic technology.