Viscosity?

 

Like 5W-30 changing to 5W-20?

 

By factors, I meant all the chemicals added into the synthetic to give it a certain viscosity. The film/viscosity of an oil that leaves a lubricating "shield" between metal parts will begin to thin so it could break down in oil weight. i.e. 5w/30 to 0w/20 and so on. But that wouldn't be that huge of a deal. I run 0W/30 now. It's the chemcials that either burn away, react with O2 and turn into acid or sludge..........that's what will begin to break the lubricity of the oil.

 

The first question was, in the non-running engine, how long does the oil stay good, and you answered it was 3 months.
The next question was, after 3 months sitting in the non-running engine, what makes fresh clean oil lose its "lubricity"?

 

^ its not moving so its settling in a metal container. Something not moving will break down. Thats why oil comes in a plastic container that is sealed.

 

Also, the fact that oxygen is continually around the engine inside and out, it's constantly reacting with the oil whether sitting still or while the engine is on. That's what keeps it constantly breaking down and what will make it lose it's lubricity. If you could vacuum seal your motor, then yes, your engine oil would basically "never" break down. But, since there's always O2 in the air around the oil, it will break down no matter what.

 

Some of those plastic oil containers are leaking oil in the store. I always ask for double bagging on those, but never realized that oil was losing lubricity on the shelf. In the old days oil came sealed in foil-lined cardboard cans with flat metal ends you had to open with a churchkey can opener. Maybe that was to keep the oxygen out.

 

Yeah, most likely. Just like K&W Motorflush; it comes in what looks like a coffee can and air tight. I think that is why they store it like that.

 

is lubricity even a word?

 

yup.

http://www.google.com/search?hl=en&q...e%3A+lubricity

 

Sorry all, i just read the thread entirely. Imo, what is most important is that 5w30 is 5w30 whether or not it's conventional or synthetic oil. However, synthetic oil should lenghten the "main seal" life. I could be wrong.

 

^ im wondering really if 5w30 is what should be used w/ the s/c because the last few days have been cold and I was getting this gear sound for the first ten min that my car was running. After the oil warmed up (i guess thats the reason) the noise went away. It was warmer today ....no noise... go figure.

 

I ran my 80 Rabbit on Castrol 20w50 for 6-8k per oil change drove it 163k miles and it didn't smoke even without a cat on it - it rusted away before the engine failed from lube failure. Typically I would change the oil twice a year and the filter once a year. On my xB I broke it in with the factory oil and changed to Synlube 5w50 and I should be changing the oil again in about 150,000 miles or 15 years with only a filter change at 36,000 and 75,000 miles.

 

^ cant wait to hear people w/ this one.

 

I spit up my beer.

 

hahaha, whatever works for him. I, personally, would NEVER do that to my car.

EVERYTHING BREAKS DOWN..............mechanical and chemical.

 

i'm almost at 30,000 miles....is it bad if i change to synthetic now?? or should i just keep using what the dealers been giving me...???

 

Yeah well if you guys knew that your cars COME with really good synthetic oil . . . then you wouldn't be asking about changing it or throwing away perfectally good oil too soon just to put more synthetic in it again.
Check out the www.synlube.com site about how and why oil breaks down . . . it will change your ideas about oil.

 

It's too much of a standard for me and any car I work on. 3000 conventional and at most 6000 synthetic are my intervals. I choose to keep constant intervals to make sure the oil stays "new."

Changing to synthetic after 30K shouldn't hurt or do anything to your car. It's on higher mileage motors that are used to having conventional oil and then the change would cause leaks. Oil seals and gaskets swell to certain points with different oil compounds. If your conventional oil has something that the new synthetic doesn't, then the seals and gaskets may shrink and b/c synthetic oil is normally thinner than conventional oil anyways, it will leak out slowly. This is coming from personal experience with 3 vehicles of my own, 2 changing to synthetic and then back after it leaked.

 

So I'm okay since I changed to synthetic when the tC was as low as 5k?