I ran synthetis in an old engine (88chevy silverado excablongbed) and messed up the engine a little. This is the order that it happened in if i remember crrectly. 1. the engine was running from poor circulation i think because of the synth oil. 2. Then a hole in the radiator hose, which was second mistake because when water was put in to make it through the rest of the day the head gasgets burned and now its got anti freeze in the oil . 3. No commpression so replaced oil pump and then realised what probbably happened(burned top end from the snyth oil and then water instead of coolant) I am new to big equipment and am learning the hard way. I will never use synthetic oil in a big truck with an old engine and always will fill the radiator while the car is on and the fluid circulating and will never use water instead of collant.