Ridge from syn oil?

[Volvohead]

Joe has it right. The heaviest wear is right under the ridge, typically only for the first inch of piston travel. That first inch is where the combustion pressures are greatest and the rings are blown against the cylinder wall the hardest.

The ridge is not new material. It is where there was no wear. The ring packs don't come up to the piston or the cylinder tops, so the wear starts where the ridge ends.

Because the rings never travel (and wipe) the full cylinder, sometimes (more commonly with carbs) you might find very some light carbon coating the ridge. It's typically fuel related. But that's about it.

I have never heard of synthetic oils causing excessive or unusual combustion chamber deposits any worse than a conventional would. It usually burns up just as well as the dino stuff does. NO oil can withstand combustion chamber temps. The oil film that a ring rides on near TDC is much thinner than a soap bubble - pretty darn close to boundary lubrication. The more common path for oil entry into the combustion chamber are the valve guides, not the cylinder walls.

It sure sounds like the mechanic/guy has overloaded on some hype and hasn't done much engine work.

 

[JetSnake]

quote:

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Originally posted by Volvohead:
Joe has it right. The heaviest wear is right under the ridge, typically only for the first inch of piston travel. That first inch is where the combustion pressures are greatest and the rings are blown against the cylinder wall the hardest.

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That sounds like something I said.

 

[TomJones76]

The only things the guy seems to be right on is that synthetic costs more than mineral-based and
"Most conventional motor oils have additives that include a synthetic component to improve thermal properties. They are cheaper than pure synth and provide adequate protection."

I'll semi-agree with him there, although on a cost-benefit basis, synthetic oils *CAN* be worth it in peculiar engines or extended drains.

 

[carock]

Gee, after my engine tear downs of customer engines running on synthetics, I see almost no ridge, and no carbon build up on the upper part of the cylinder wall. Go figure. Redline ester synthetic two stroke oil burns cleaner than the dino two storke oils, leaving fewer deposits. Go figure.People who claim that synthetic oils do not protect a car better than dino oils have not done real world engine inspections. I don't know about the cost/benefit arguments for synthetics, but if you are looking for decreased wear at any cost, use a good synthetic. If you own an expensive car, use a synthetic, it will save you $$$.

 

[Volvohead]

I'll have to tell all my buds with 250k+ mile slant sixes they had better nicacil their cylinders or else.

If this involves a two cycle engine, then he's talking about pecans in a conversation over oranges.

 

[JetSnake]

Nicacil plating an automotive cylinder would not be needed even though nicacil plating lasts much, much longer. The cylinder would fare outlast the vehicle. It sounds like you are trying to be difficult.

 

[Volvohead]

No. I just disagree with your assertion that cast iron is an inferior cylinder material, given its proven design success over many decades, in both diesel and gasoline engines.

I'd take a cast iron block or liner over Nikasil plated aluminum any day where durability was at issue. And I think quite a few BMW owners with would agree with me.

Seems you do too, given your last comment that it is not needed.

 

[Volvohead]

Oh, come on now carock. "Almost no ridge" means SOME ridge, and only a newbie or an idiot would force a piston past ANY ridge. They've all got a ridge past a certain mileage.

We weren't talking about its height or size, just its origin. I think all the older hands here agree that cylinder ridges are the result of wear, and not combustion byproducts.

Synthetics are superior at the operating extremes. But at moderate change intervals, a top conventional wears no worse than a synthetic in an average engine after break in. It can leave behind more deposits if maintenance gets sloppy. But don't confuse deposits with wear.

And why are you tearing down engines running on synthetics if they wear so well?

 

[JetSnake]

Well, he's talking about two stroke oil and if he is looking at the cylinder of a snowmobile which has a nicacil plated cylinder, then no, no wear will be found.

Nicacil plated cylinders are a lot more resistant to wear then inferior cast iron cylinder found in car engines.

 

[carock]

We have to tear down engines that wear well because the Europeans have been trying to save too much money on seal suppliers. Also, the more expensive the car, the more likely it is to overheat. I can't tell you how many cars we had that overheat in traffic.When will they ever learn...

 

[JetSnake]

I don't know what your deal is. Is it how I worded the statement I made about cast iron bore being inferior? If it makes you feel better, I have a cast bore in my S-10.

Nikasil can be applied to cast iron bores as well. Nikasil dissipates heat better and provides better lubrication then cast iron. When used with the right rings, it also provides a better seal with less blow-by. It is general less expensive to rebuild an engine with Nikasil plated cylinders. You just hit it lightly with a glaze buster and your good to put in the new pistons. Also, if you do have a catastrophic engine failure where damage extends past the Nikasil plating, you can have it repaired by welding the damaged area and replating the cylinder. It saves you a lot of money verses buying a new cylinder for a snowmobile. I've had it done my self and had no issues with it.

So you learned something new. It's not that big of a deal, absorb it and tell all your friends your new knowledge. Have a good day.