thats not what i have heard or seen,but all there own stevo.

 

That "don't use synthetic oil on an old dino-oil engine" scare tactic is a rumor that's been floating around for many years. It is based on OLD experiences during the early years of synthetic oils. One complaint was the synthetic oil "shrank" the oil seals creating a leak, or the synthetic oil "found" leaks that weren't there with dino oil. That is not the case with today's synthetic oil, it's a different animal. The simple fact is, synthetic oil is far superior to dino oil, no matter how new or old the engine.

 

synthetic oil will not shrink seals or gaskets or even force them to leak. what it does is exposes a faulty gasket that was already there. the gasket may have had a tiny open or broke spot that got filled with gunk which was keeping it from showing any signs of wear, all the synthetic oil is doing is cleaning all the gunk out of your motor including the insides of the gaskets which will expose a faulty gasket if it is there. when switching over to synthetic oil, the first 2 uses it is best to change it out between 1000 to 1500 miles because it is cleaning everything out of your motor. after the first 2 changes (and i say 2 as max, 1 is usually enough) you should be fine for a much gr8ter distance and much more protecting than that of regular oil. syn oil is NOT thinner than reg oil but is is slicker because it has a much higher film strength than reg oil and it keeps parts from creating more friction which in most cases will also lower your operating temps a bit too. those are the facts bout syn oil plain and simple it is 100% better, i use royal purple in mine and its the best stuff iv ever had although mobile 1 is good too, most synthetic oils will do but if you drive it really hard a lot i would recommend royal purple or red line my opinion on your tap sounds like to me it could be piston slap since it only does it when its cold and goes away when it warms up. i know piston slap is more common in the v8's mid 90's but it is a slight possibility. anyways didn't mean to write a book here oh and ps 5w-20 is a bit thin after 75k miles you may try 5w-30 or even 10w-30, its just a thought.

 

Most of what I've read is from the powerstroke magazine my dad used to subscribe to. They always ran tests on oil. In several of their articles, they said that you'd be better off buying walmart oil, and changing it often, rather than buying expensive synthetic and changing it less often. They also say that you should use the same type of oil for the life of the vehicle. Now granted powerstroke magazine is strickly about the ford powerstroke diesels. But to me, oil is oil. We used walmarts cheapest oil in Dad's old aerostar van all the time. If you know anything about those vans, you know they have terribly un-reliable engines in them. We ran it for 385,000+ miles, always using the same cheap oil. But we did change it every 3000 miles.

Sythetic is good stuff, I never said it was bad. I just am saying that it's best for the engine to use the same oil in it from beginning to end.

 

My car did that and it was the lifters... Best thing to hope is to put in Lucas Oil Stabilizer or switch to synthetic oil and hope it goes away.

 

The basis for that comment is old and outdated, and pertains to the OLD type of synthetic oil. That is no longer an issue with current synthetic oil.
Here's some good oil info to read, especially read the part titled "Mixing Mineral and Synthetic oils": The Engine Oil Bible
Here's another good source of oil info and testing. And if you're thinking about using an oil additive, click on the "What about Additives" tab: Bob Is The Oil Guy

 

Guess I'm a little outdated then. It was an article I read a few months ago, where they ran a lot of tests. Maybe there's something different when it comes to a diesel then. Then again, you're talking to the guy that grew up around family mechanics who are old school, and a lot of what I learned came from them. My grandpa still won't use multi-viscosity oil . That stuff was crap when it first came out. So I guess ignore what I said, and change your oil with expensive synthetic oil every 3000 miles, ain't my car anyways.

 

Why would you change a synthetic oil at 3k miles? One of the principles of a synthetic is a much longer life before it breaks down as compared to regular oils.
I don't know the recommended interval for Mobil1, but Amsoil recommends anywhere between 15k to 35k miles, severe to normal driving conditions respectively: Amsoil Drain Chart
I don't think I would stretch it quite so far myself. But you get the idea, that you can go one hell of a lot further than regular oil.

 

Or let me put it a simpler way, since you brought up the extra "expense" of synthetic oil. Let's say that synthetic is twice the price of conventional oil, which is pretty close to accurate.
Change the regular oil at 3k miles, or change the synthetic at 6k miles (which would not be out of line at all). So you broke even on the oil cost, but with the synthetic you had to deal with one less oil change and all the B.S. that goes with it.

 

I still wouldn't run it that far. I'd feel 10x's better about my engine changing the oil often using inexpensive oil. There's just no changing my mind about that. By changing my oil often, I can keep a very close eye on how it's doing. It's just a personal thing, I like to monitor every aspect of my car.