Full Synthetic Oil Question

[Black on Black]

I have heard that if you have given your car regular oil for its lifespan, you should not switch to full synthetic as old oil buildup will start to come loose and mess with your engine. Would it be wise not to make the switch now?

[Toysrme]

Yes, that's a load of crap leftover from the 70's.

Like... Drilling holes in brake rotors because "brake pads give gas when you heat them".

[monarch]

Try searching all the forums using "synthetic leaks" as your search words to read about the owners who succumbed to peer and advertizing pressure and switched to synthetic and then wished they hadn't because now they have oil leaks that would cost $1,000+ to fix.

[Ross W.]

Try searching all the forums using "synthetic leaks" as your search words to read about the owners who succumbed to peer and advertizing pressure and switched to synthetic and then wished they hadn't because now they have oil leaks that would cost $1,000+ to fix.

The reason synthetic oil leaks more on higher mileage engines is because A the oil molecules are consistently one size and B the seal tension is not set up for synthetic oil. Conventional oil's molecules are a great jumble of sizes; 20w50, just to pick a grade, is a mean average of molecule sizes to meet the API specification, for a conventional oil, while for a synthetic, it meets spec with a very consistent molecule size. A conventional oil will tend to have the largest molecules clump next to the seals, blocking the smaller ones. That won't happen with a synthetic of the same viscosity. Thus a synthetic loves to wick past the seals. New manufacturers that specify synthetic oil have to have seals that are twice the clamping tension/force to minimize leakage. The drag from tighter seals is offset by synthetic oil's much higher lubricity. For an engine with higher miles, its safe to run a higher viscosity synthetic. I'm currently running conventional oil in my Lexus, but I am going to switch to synthetic. My last car I ran Mobil 1. But I had to go up two viscosity grades to stop seal creep. Doing that on a higher mileage engine won't be a problem, but on a new engine or a low mileage one DON'T DO THAT! Best to stay with the same grade oil or go up one grade, but it's best to err on the side of caution in that case. All in all, my last car was noticeably smoother and got better mileage with synthetic oil. I expect the same when I switch my Lexus over.

There! I feel better now!

[cardona6569]

Synthetic tends to leak more, but is has to do a lot with, how good your seals were from the begining. The Lexus LS tend to leak from the valve covers; before going into Sync, check the condition of those gaskets, if they are leaking adjust the torque, or retorque and add a No-Leak oil sealing product and you should be ok. If you want to up the ante, replace the valve cover gaskets, then start using the new oil. If you use a 50w instead of the 30W you are sacrificing fuel economy. Second, the Japanese engines tend to have smaller lubrication ports, thus your engine may not lubricate as it should so it is in the best interest to keep using the recommended grade oil. I have switched to Mobil 15,000 and is working fine, no leaks or problems.

C. PR

Try searching all the forums using "synthetic leaks" as your search words to read about the owners who succumbed to peer and advertizing pressure and switched to synthetic and then wished they hadn't because now they have oil leaks that would cost $1,000+ to fix.

The reason synthetic oil leaks more on higher mileage engines is because A the oil molecules are consistently one size and B the seal tension is not set up for synthetic oil. Conventional oil's molecules are a great jumble of sizes; 20w50, just to pick a grade, is a mean average of molecule sizes to meet the API specification, for a conventional oil, while for a synthetic, it meets spec with a very consistent molecule size. A conventional oil will tend to have the largest molecules clump next to the seals, blocking the smaller ones. That won't happen with a synthetic of the same viscosity. Thus a synthetic loves to wick past the seals. New manufacturers that specify synthetic oil have to have seals that are twice the clamping tension/force to minimize leakage. The drag from tighter seals is offset by synthetic oil's much higher lubricity. For an engine with higher miles, its safe to run a higher viscosity synthetic. I'm currently running conventional oil in my Lexus, but I am going to switch to synthetic. My last car I ran Mobil 1. But I had to go up two viscosity grades to stop seal creep. Doing that on a higher mileage engine won't be a problem, but on a new engine or a low mileage one DON'T DO THAT! Best to stay with the same grade oil or go up one grade, but it's best to err on the side of caution in that case. All in all, my last car was noticeably smoother and got better mileage with synthetic oil. I expect the same when I switch my Lexus over.

There! I feel better now!

[steviej]

Try searching all the forums using "synthetic leaks" as your search words to read about the owners who succumbed to peer and advertizing pressure and switched to synthetic and then wished they hadn't because now they have oil leaks that would cost $1,000+ to fix.

After you try monarch's search, then do a search on "synthetic" and read all the endless posts of people that switched with high mileage and nothing happened. If an engine had regular oil changes throughout its lifespan then chances are it was/is well maintained, the internals are clean with very little build up.

Now, as always, here is the warning. If this becomes a rehash of the age old "oil debate" that we all hate to spend time reading but love to post in, it will be shut down. There are currently too many oil debates and threads throughout our database, so please, if you want to ask "which is better, dino or synthetic?", then search for it. We will not maintain oil debate threads unless someone has posted totally new information.

I understand some of you are new, but this discussion opens many heated posts and creates tension between members. Until new information arises, this oil debate horse is beaten and dead.

steviej

LOC Management.