Synthetic oil to standard switch.

[Scott Macinnis]

I went to one of those quick lube places last August for an oil change and you young guy working there put synthetic in my 2005 Toyota Tundra. I had never used it before. He assured me that it would be fine, but might just burn a bit for the first 5000K Well it burns more that a bit. About a litter per week. It’s pretty embarrassing because when I have been driving if and shut it off for a few minutes, when I makes a huge plume of blue smoke. So needless to say, I’m frustrated. The Truck only has about 140K on it. How can I fix this? If I switch back will I it do damage? I didn’t burn a drop of oil before this.
Please help!!

Topic

[Bill]

I don’t know that the synthetic oil caused your problem but when I bought my van I used synthetic in it and it used a lot of oil. 20000Km later it slowly stopped burning oil. I still use synthetic.

Switching back to regular oil should cause no damage to the engine.

[Scott Macinnis]

I’ll switch back and see what happens.It just burns so quick I’m worried I may run out one day.
You must have burned a lot of oil over 20000km

Thanks

[Lorrin Barth]

I know there is much discussion about oil on every car forum. It is endless. I started exploring the use of synthetic oil back when Mobil first introduced their synthetic product. Right away I learned that synthetic oil was not the same when I saw my oil pressure approaching zero.

Here is my advice:

Engines that call for synthetic oil are designed for synthetic oil and engines that call for conventional oil are designed for conventional oil. Can you use synthetic oil in an engine designed for conventional oil? Yes, you can but you need to be willing to play car engineer. You may need a different viscosity than what the owner’s manual calls for if using synthetic oil. So, you should only try this in a vehicle with an oil pressure gauge.

Other than that, switching back and forth between synthetic and conventional oil is no big deal. I have done it many times.

[cptbarkey]

sounds like the blue smoke means other things and is unrelated to your choice of oil.

http://answers.yahoo.com/question/index?qid=20100422094353AAR3qoW

[george gonzalez]

Blue smoke on startup is very often, like almost always, caused by valve stem seals that are not sealing so good anymore.

You see there are these little rubbery or neoperny sals that slip over the valve stems and are supposed to tightly hold onto the stem and keep oil form running down the stem into the cylinder.

These often either get rock-hard and don’t seal so well, or they go limp and don’t seal so well.

So when you shut off the engine the oil drains down between the seal and valve stem and drips into the combustion chamber, and makes a big cloud of blue smoke on startup.

It doesn’t happen so much while the engine is running, because the intake valves run pretty cool and those seals tend to last longer, and the exhaust seals can go bad, but there’s always positive pressure pushing up almost all the time the engine is running, so the oil doesn’t get a chance to drain down the exhaust valve stem while the engine is running.

Now synthetic oil may be a bit runnier, the jury is out on this, and it might just drain down a bit more. Or others will say that the synthetic oil will (maybe) remove old sludge and varnish that was helping seal the valve stems and other seals.

In any case, there may be a bit of truth behind the story that synthetic oil “makes” your engine leak. The truth may be a bit more nuanced, if it’s the synthetic oil cleaning off old sludge and just revealing old leaks.

In any case, changing the valve seals is not a huge deal on many cars, you bring the piston all the way up, slide aside the cam follower, push a bit on the spring, remove a c clip, pull off the old seal, then reverse the procedure with the new seal. You can do two seals a minute. Another minute to set the valve clearance. Depending on the car, you may have to buy or rent a special spring compressor tool if the springs are way down in the head.

[Chris]

[quote=”grg8888″ post=81839]Blue smoke on startup is very often, like almost always, caused by valve stem seals that are not sealing so good anymore.

You see there are these little rubbery or neoperny sals that slip over the valve stems and are supposed to tightly hold onto the stem and keep oil form running down the stem into the cylinder.

These often either get rock-hard and don’t seal so well, or they go limp and don’t seal so well.

So when you shut off the engine the oil drains down between the seal and valve stem and drips into the combustion chamber, and makes a big cloud of blue smoke on startup.

It doesn’t happen so much while the engine is running, because the intake valves run pretty cool and those seals tend to last longer, and the exhaust seals can go bad, but there’s always positive pressure pushing up almost all the time the engine is running, so the oil doesn’t get a chance to drain down the exhaust valve stem while the engine is running.

Now synthetic oil may be a bit runnier, the jury is out on this, and it might just drain down a bit more. Or others will say that the synthetic oil will (maybe) remove old sludge and varnish that was helping seal the valve stems and other seals.

In any case, there may be a bit of truth behind the story that synthetic oil “makes” your engine leak. The truth may be a bit more nuanced, if it’s the synthetic oil cleaning off old sludge and just revealing old leaks.

In any case, changing the valve seals is not a huge deal on many cars, you bring the piston all the way up, slide aside the cam follower, push a bit on the spring, remove a c clip, pull off the old seal, then reverse the procedure with the new seal. You can do two seals a minute. Another minute to set the valve clearance. Depending on the car, you may have to buy or rent a special spring compressor tool if the springs are way down in the head.[/quote]

Yes well said, on an older vehicle, switching to synthetic (which has various of detergents that conventional may not) may clean out old gunk that was helping seal your valve stems among other things…
The switch to synthetic is likely what caused the blue smoke and the oil burn but not necessarily because the synthetic damaged parts, but rather, because it exposed a preexisting issue.

as far as the latter part of the question, switching back will NOT damage anything. Synthetic and conventional do not have any problems when mixed or combined, although… and this is a big although… I wouldn’t expect to see any major improvements… the synthetic likely cleaned or at least dislodged any old goo that was sealing your worn seals and they will likely still leak after the switch back to conventional.

AS far as the statement that synthetic is more runny… this is by definition FALSE. The oil is designed to meet certain viscosity requirements, this viscosity rating defines the fluids ability to deform under shear stress: the more viscous, the less it deforms. these viscosity ratings for example “5w-40, 10W-30… etc” define the fluid’s ability to deform continuously due to shear stress. More so… these ratings were and are created independently of the fluid they are describing… conventional or synthetic. The misunderstanding that conventional is less runny than synthetic originates from the fact that synthetic oil reaches its rated viscosity level faster. IE
When you turn on your engine, the oil is cooler than operating temp. and therefore more viscous. conventional oil takes longer to warm up and reach the rated viscosity than synthetic oil. But that being said at normal operating temp both synthetic and conventional oils of the same viscosity rating will have the same viscosity.

Hope this helps
Chris
sources: experimentation and incompressible fluid analysis and various online sources…

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