This is a discussion we have had with Mike for a while now. > > I don't use synthetic, #1 because it costs a ton and > #2 because I don't think the benefits for my 67 > iMperial are that much more than using a good > conventional oil. Synthetic oils leak more, so unless > you have a newly redone engine with nice, tight seals, > you will find more leakage. This may not be a major > concern- heck, you may even appreciate the perpetual > front chassis lube. But, your oil consumption will Both my 440s have Mobil 1 15w50 (I live in the warm south) and my "new" 67 volvo also got the same treatment. I have to agree with Mike that it appears the leaks go up with synthetics. Also, there is no doubt that the wear goes down as well. This pays off more if you drive your car hard, which both Mike and I do. Mike raises the legitimate question: As the 440s have relatively low specific power (by modern standards) and since they are very durable engines anyway, will the higher cost of the oil pay back? I cannot answer with confidence on this, as it requires many statistical studying and testing etc. However, part of the deal is emotional. When I open all the 4 barrels on the open road (or 4 air doors as some have joked) on my 440s, I like to know that the engine has the best possible protection. Also, if something nusty happens, like a serious overheating (as it has happened before) the Mobil 1 will give your engine the best protection. You add the better flowing abilities of the Mobil 1, and extended drain, and its not a bad deal. In fact, as my 440's lose oil at the rate of a quart per 1000 miles (mosty leaks, but one of them has bad valve guide seals), I very rarely change the oil (but change the filter every 3-4K), but in the same tme, I almost never do any short trips with them (that's what the volvo is for, and the little 4 warms up very quickly). Now, if you are the type of person that hates a dirty engine, sythetics may not be for you. > increase as a result. I have also HEARD (and take > this with a grain of salt) that synthetic oils do not > cling to metal parts as well as conventional oils, so > cold starts can be more damaging, esp with engines > with large clearances. The newer synthetics may not > have this problem. Sorry Mike, as discussed before, this does not hold any water. If the clearances are larger, use havier oil. The oil pressure at a hot idle indicates if the oil is too thin. In fact, the same proterty that makes synthetic leak, also help them flow better under low temps, so the cold start/dry start wear should go down. Having said all that, we have to emphasize all modern motor oils pass certain requirements, and as a result they were ALL better than what you could find back when our cars were new. Some distinguished members in the list use single weight oils. Even though all these oils are well engineered, there is no reason to not follow progress, and progress (since the early 60's) were multi weights. So, unless you live in a place like Hawai (like our distinguished member lives), it makes no sense to use single weight oil. D^2