I've been running valvoline max life products for years now. They used to make a conventional oil but have now gone to synthetic blend and full synthetic. I still run the synthetic blend. But was wondering about the old rule of never switching types of oils (conventional to synthetic.) Is this still a rule or has it been proven a myth. The reason I ask is that I've heard awesome things about Amsoil. I checked their site and it seems they're strictly full synthetic. If its a myth would it hurt any of my vehicles due to high miles to switch. My 96 Buick has 188k and my 00 f150 has 155k. I'm going to continue running valvoline in my 90 f150 for now.

 

Switching to synthetic doesn't hurt anything and I've never heard an allegation that it does. What can happen though is this: synthetics lubricate better and they flush sludge better. If you have any incipient leaks that are being prevented by crud, the synthetics can remove that crud and will begin to leak. They do not cause the problem (worn or defective seal/gasket) they merely reveal it.

 

If they aren't currently burning or leaking oil and are not sludged up, it should be safe to switch.

 

it'll be alwright i use mobile 1 in my car

 

It may be a myth, I can't say. And it may have been true on the older engines and with the older oils, but my dad was a mechanic and he taught me to never switch. I have never done so, and have never had an engine burn oil. There have been quite a few, too. On my truck, I have 116,000 miles, running the Motorcraft 5-20 blend and it drops about 1/16 of an inch on the stick, between changes. I change it at 4000 to 4500.

 

I have gone back and forth between a syn blend and full syn on my DD ever since I bought it. I switched to full syn at ~83,000 miles and have gone back to syn blend about 6,000 miles ago once the full syn went back up a bit in price (though, I was running an 8,000-9,000 mile OCI). There's no harm; just full syn can clean better and can "reveal" a leak that was plugged up with crud that non-syn couldn't remove.

 

Its a myth. I switched to full synthetic from royal purple at about 40,000 miles and my edge showed a 16 degree drop in ECTs. Went from 206 to 190! Never had any problems and I will continue to buy synthetic till the day i die. Now I cant prove this next statement but I heard it was bad to switch from SYNTHETIC TO CONVENTIONAL because the synthetic tries to remove (clean) the conventional oil but when most of your oil is conventional it will just gum up. Probably would have to add some sort of stabilizer. but like i said this is also a myth. Can anyone prove or disprove this?

 

you can go from conventional to syn blend or syn blend to synthetic or synthetic to blend or syn blend to conventional, but i have always herd that you SHOULD NOT go from syn to conventional.

 

Never heard fact that says you can't go from syn to conventional. Heck, syn blends are a low % of actual synthetic. They are mostly conventional oil.

 

With today's oil technology, there really isn't much difference between any dino, semi, or full syn oil.

 

A) Synthetic oil can reveal leaks, so watch the oil level carefully after the change, and for the next few changes.

B) You're already running synthetic, so you shouldn't have any problems, but check the level anyway.

C) 100% full-synthetic and synthetic blends contain 0% synthesized oil. All are merely highly-refined natural (dino) oil that behaves exactly like early synthetic oil did. Do some Googling about when Mobil1 sued Castrol.

http://www.bobistheoilguy.com/

 

This is about GrpIII oils, yes? GrpIV and V, AFAIK, aren't refined (hydrocracked) syn-oils?

 

You can switch anytime and back and forth all you want today. That was not true exactly back in the 90's. Most synthetics were of the Gp IV variety which means they were a PAO basestock. PAOs had more solvency than the dino base oils of the day. You could easily have a marginal seal that didn't leak from varnish from the dino oil that a PAO may cleanout causing a leak. There was also the viscosity. While you may know oil as a 5w-30, that's the SAE rating. The industry goes by a much finer scale. Synthetics were often formulated to be just inside the thin end of the viscosity range. The "thinner" oil made for leaky seals. PAOs also do absolutely nothing for seals. The materials used for seals requires the oil to provide a "seal swelling agent" which dino oil provide naturally. So as much as some of you love yer synthetics, they are not a cure all and come with a host of issues.
Todays synthetic oils are mostly a Gp III base, even those that have been for many years a PAO base oil. There are very few left that are a PAO only base. Some of the mentioned oils are a Gp III with a splash of PAO. Doesn't make them a bad oil nor does it mean you are getting less than what you previously bought. It means that the ethylene gas used to make PAOs has become hard to find and expensive. The formulators have now made the base oils and add packs to equal the old base oils and in most cases, the product is better.

The blends are usually a mix of Gp I and Gp III base oils. Depending on the brand determines how much of what is in the bottle. Motorcraft, the last I had on them, was right at 60% Gp III which is a lot for a blend. The GpI oils are solvent refined. The Gp III oils are generally a severely hydrocracked oil which means they are a gas to liquid AND liquid technology. The Gp IVs are generally known as the PAOs. They are a gas to liquid technology and made in a refinery. Most of these types of base oils come from the south around the Mississippi River area over to Houston. The Gp V oils are everything else but is mostly thought of as the esters. Esters are a reaction of a fatty acid and an alcohol. Esters are the only base oils that brings a hair more lubricity to your engine. But it's so small you and your engine will never know it. With todays oil technologys, there is no reason to use any of the synthetics unless extended oil changes are ideal to keep the unit on the road. There is NO more lubricity in any synthetic oil that is usable in your engine. Any formulation of the add packs in a synthetic that brings an advantage can also be used in a dino based oil with equal results. Yer truck, yer money, and you are the one making the payments. But when was the last time you saw an oil related failure? It doesn't happen often and there are a lot of engines on the road today with several hundred thousand miles on the clock using Walmart oil. Chose wisely, grasshopper.

 

And with that I think ill just stick with Valvoline. Thanks guys for the replies and special thanks to labnerd, cause now I'm going to see if I can research everything he said so that I can better understand it. I haven't seen so many acronyms since I was in the Marines. LOL

 

Check out the BITOG link I posted - it has more info than you ever wanted to know about oil.