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B-maniac
11-24-2006 06:13:53
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Brief history; Guy with 8N posts "will it hurt if I use synthetic oil in it"? Dr.sportster says,in his air-cooled bike it runs way too hot on oil temp guage. Everyone wonders what the oil would have to do with that? I jumped in too,and told dr.sportster he must have other bike problems for that to happen. I want to opologize to dr.sportster, right here,for after giving it a lot more thought,I believe I have the answer to the dilema.See if it makes sense to you guys. It does to me...Oil has a couple other functions besides lubrication. Cleaning and cooling. The oil's cooling job is a whole lot different in an air cooled engine than it is in a liquid cooled engine. In a liquid cooled engine the coolant circulates in the head taking away the majority of the heat,leaving the oil very little cooling to do,plus the cooling system will regulate the temp anyway...On an air cooled engine (assuming ohv or ohc with oil pressure up in head) the oil is the first thing to contact the hot head surface on it's way back to the crankcase. It absorbs heat even BEFORE it can get to the cooling fins to be cooled by the air passing over them. Because of this , an air cooled engine SHOULD have an external oil cooler if it didn't from the factory. There IS nothing else to cool that oil, which is acting as a coolant! Now,back to why synthetic runs hotter than reg oil in this situation? We are right back to the fact that it is superior oil in ALL it's duties. Including COOLING. It penetrates , sheets , wets the metal better and, in my opinion, then absorbs heat better , which puts more cylinder head heat into the oil , BEFORE it can get to the fins. Take into account , too , when the bike is sitting still , there is virtually NO cooling going on with the fins. Bottom line is this. Dr.sportster is probably right when he says that synthetics may not be the right thing to use in an air cooled V-twin bike. I will have to add this , to that. Synthetic oil , in this case , is it's own worst enemy. It does it's job (cooling) too well, and therefore in this application , becomes too hot. My solution would be use an external cooler so that you could still take advantage of the superiority of synthetic oil. I reallize this may not be an option in many cases , for originallity and/or logistical constraints. Very few bikes ever see the severe use that an everyday driven car sees, and as such will probably never know what oil is in it's crankcase. Some people just want the best , whether it be in their car/bike or even old tractor (hense all the tractor posts on the use of synthetic oils). This one "disadvantage" if we may call it that , with using it in air cooled engines is something I never would have thought of had it not been for dr.sportster's post. Again , I appologize to the dr. , as I do believe he had a very valid point, and anyone with air-cooled bikes without oil coolers , or without sufficient coolers , should probably re-think the use of synthetic oils, if for no other reason than it cools the head better and quicker than the air does. In a liquid cooled engine , though , I would use it , and do. I have read all the independent oil tests and mileage analyses on these oils , and my eyes , and even the test staff's eyes were opened to the real world advantages of synthetics. I'm not going to get into diesels , as they have different requirements. They are a dirty engine (relatively) and at the oil change intervals required by factories , may not be economically feasable to use these oils. Have a great day , all , and dr.sportster,sorry.
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