switching to synthetic

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mopar_1974

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hi, i saw a topic on oil for a new engine earlier today and it brought up something that i have been wondering for a long time. switching to synthetic. I have heard good things about synthetic oil but have heard bad things happen when switching. back in high school my shop teacher told me that the best bet is to stick with what you have. however, others say synthetic is the way to go. I remember a freind switched to synthetic in his 72 el camino and about 2 weeks later his engine blew..coincidence? possible. i've seen people switch to royal purple and get a small increase in hp. things must be running smoother there. i just want to know what you guys think.
 
I've been running Mobil 1 in my family vehicles since 1980 and do it for 2 reasons. The first is that Mobil 5W-30 has a pour point of minus 40 deg where as conventional at that temp. is "tar" at minus 40. So lets say it's minus 25 outside tonight and the wife forgets to plug in the block heater. I can start the car in the morning and I'll have oil pressure immediately whereas conventional you'll wait 5-10 seconds which means wear. The other reason is that since "true" synthetic oil has a stronger chemical bond between the carbon molecules the oil doesn't break down, due to heat and load, as fast as conventional oil. For this reason I change the oil every 6-8000 miles and if I go over no big deal.
You still need to change the oil regularly since it gets dirty and contaminated with water and other nasties. Forget about increases to milage and horsepower because the salesman can play fast and loose with those numbers and are pretty hard to prove unless you're running a high horse engine on a dyno.
I never run synthetic in my muscle cars for a couple of reasons but mainly because synthetics will find every place possible to leak out of and do.

Terry
 
demon seed, I agree with all points but the oil leak thing. Being synthetic oil molecules are larger than air molecules if a motor will leak when sythetic oil is put in, it means that air and dirt can get into the motor. This is not a very well gasketed/sealed motor and has/will have bigger problems than an oil leak. I run sythetic or synthetic blend in all of my vehicles including lawn mowers and farm equipment regardless of age and have no issues with leaking.

I would also add that the gaskets and seals that we put in our older cars are no different than the gaskets and seals in the newer cars.


Chuck
 
It is important to note distinctions between what are now categorized as "synthetic" lubricants:

http://www.chevron.com/products/prodserv/BaseOils/docs/ebot.pdf

I've found that the GpIII stuff made by Shell (Rotella T-Syn), is less prone to the seepage/leaking phenomenon often attributed to synthetics. As is detailed in the paper linked above, modern gpIII motor oils are now on a par with and in some areas even surpassing the performance characteristics of the original PAO-based synthetics.
 
The other reason I don't use synthetics in my muscle motors is all have had flat tappets. I've seen test reports that show that because of the more slippery nature of synthetics over conventionals the lifter does not always rotate in it's bore. This will cause a less than universal wear pattern on the face of lifter and cause wear to occur on the cam lobe.

Terry
 
Ace, that is an interesting paper. The only problem I see is if I'm at the parts store how will I know if the petro oil is made out of Group II or Group III base stock? I will look next time I am at the store and see if it says on the bottle.

Chuck
 
I'd have to do some label reading myself. One sure way to tell is the gpIII is almost always cheaper, at least the Rotella and Castrol stuff is. XOM has recently been moving some of their stuff to a gpIII base, but INCREASING the prices (Mobil1 EP, for example), so the lines are getting blurred.

As far as "slipperiness" goes, that's a new one on me. I know the lower levels of zinc-derived additives found in the latest EPA-mandated API standards classifications are an issue. But I can't understand how more slippery would translate to less movement in terms of an abnormal wear pattern. :dontknow:
 
Ace, I could see how if something is supposed to have a certain amount of friction to make it work correctly, not work correctly, because the friction is less than required or no longer there. One of the reasons roller cams need stiffer springs is so the friction of the roller against the lobe is greater than the friction of the bearings inside the roller so it "rolls" instead of sliding on the lobe.

I'm not going to discount that statement because there is a certain amount of logic in it.

Chuck
 
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