oil gets less slippery with use?

[oilyriser]

I've noticed this a few times now. The last three times, after about 4500 miles, I started to feel more engine vibration. After 7500 miles it was quite strong. Fresh oil made it run smooth again. After 7500 miles, the oil had thinned to 9.2 cSt, and after 5600, to 9.5. My last oil was 5w20, which starts at around 8.5 cSt, so I figured the engine vibration would be really bad, yet the engine ran as smooth as with fresh 5w30. But again, after 4800 miles I was starting to feel a bit more engine vibration, and putting in a fresh batch of 5w30 cured it. I even kept the old filter, so this was only from the new oil.

The reason I changed it so soon this time was because the timing belt tensioner failed to pump up quiclky, a few days ago, and I heard the loud sound of the belt slapping against the plastic cover, so I figured the oil was not keeping things clean enough at that point. But maybe it was the loss of slipperiness.

Does anyone else notice increased engine vibration after 5000 miles or so?

 

[Clyde65]

I attribute your engine vibration to the oil shearing down after 3000 miles. After 7500 miles, sure hope you're running synthetic. Dinos start shearing out of grade after 3000 miles. By 4000 miles, they can be one full grade below. The main thing you got to watch out for is the TBN. 3.5 is considered good with 1.0 being shot. So if you want to keep the vibration away, run your oil to 3000 miles and change it out. What I do, is start out with a 10W-40, and even up to 4000 miles, the engine is still smooth.

 

[dave1251]

Clyde65 I am not even going to start. oilyriser what is your car and how many miles do you have on it?

 

[Prelude]

It's not really an oil problem but it is oil related. Check/replace the spark plugs, check the compression, do an UOA. A bit surprised that a bitogger would go that far being aware of a problem. I had a similar trouble a number of years back when they used MMT as an octane buster. I also tried different oils and I found that Esso Ultra (it is sold only at Esso outlets) worked the best even in a troublesome engine. Needless to say that the problem was gone after the spark plugs were replaced.

 

[oilyriser]

This is an 01 Subaru 2.5L, normal aspirated, with about 70,000 miles. I suspect the friction modifiers don't last all that long.

UOA to come, some time later this week.

 

[friendly_jacek]

quote:

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Originally posted by oilyriser:
This is an 01 Subaru 2.5L, normal aspirated, with about 70,000 miles. I suspect the friction modifiers don't last all that long.

UOA to come, some time later this week.

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You might be on something, check the threads on ZDDP depletion.

However, I had 00 subaru and didn't notice any difference with my 5-6000 changes. Once I did even before and after oil change noise comparison as I was going from 5W30 to 5W40 (no difference).

I would not use 5W20 in subaru unless you do short trips only.

 

[mechtech]

My old 320i would start using oil at 2,000 miles, and didn't feel the same, either.
Shearing is the most probable cause for your car, with particulate matter contributing.

 

[Clyde65]

quote:

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Originally posted by dave1251:
Clyde65 I am not even going to start.

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Oh oh ...