"Think Twice About Switching to Synthetics"

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Aug 10, 2004
High in the Mountains of Central California
A very interesting article that came in today's "Lube-Tips" email newsletter...


Q & A: Think Twice About Synthetics

"I am considering replacing the mineral oil in my engine with a synthetic oil. The engine has 50,000 miles on it. I have heard that the mineral oil and synthetic oil are compatible. Is this true?"

Generally, the reference to synthetic oil for an engine, means a lubricant is formulated with a polyalphaolefin (PAO) base oil. PAO, which is often called synthesized hydrocarbon, is pure and is compatible with mineral base oils.

However, because the PAO base oil does not dissolve additives effectively, it is usually formulated with an ester co-base (usually di-ester and/or polyol ester). The additives are soluble with the ester and the ester is soluble with the PAO.

Likewise, the PAO tends to cause seal shrinkage and the ester causes seal swelling, so the effects are offset when both base oils are present. It is the ester that can cause problems when one changes from mineral to synthetic.

Ester base oil used alongside PAO base oil in lubricant formulation has excellent natural detergency. In other words, it will clean up varnish on component surfaces as a result of thermal and oxidative degradation of the lubricant. When one switches from a typical mineral-based engine oil to a typical synthetic-based oil, the varnish layer will be removed by the ester in the synthetic oil and become suspended.

This suspended material can rapidly clog filters and can block oil flow passageways and lead to component starvation. The same is true for gearboxes and other industrial machines.

So think twice about switching to synthetic oils in applications where the engine or other machine has been operating for some time with mineral oils. If you decide to make the switch, try to clean the system before making the change, then monitor it carefully once you start it up.

Drew Troyer, Noria Corporation

If the above is true, then when one switches to PAO/Ester synthetics (from mineral-based oil), it ought to be treated like an ARX treatment, with an initial short OCI and filter change.

What do you all think?
I think I'm still going to change my sisters oil and filter at 7500 miles. Although if that's true I should be worried because I never used ARX on her engine with 80K miles. But I thought synthetic oil gradually dissolved contaminates?
I think it's a bunch of goo-goo guy-pan.

I've heard crap like this for over 15 years. If you want to switch to synthetic, go ahead.

If you want to go past the manufacturer's reccomended drain interval, you need to do so with caution and used oil analysis and the testing laboratory's reccomendation.

I wouldn't just strike out from doing 3,000 mile OCI on dino and go to 10,000 mile OCI with synthetic. I'd go the reccomended length and then test it.
If you have a badly sludged engine, I can sort of see this guy's point.

But if you've got a badly sludged engine, just running it could break of some gunk and clog a filter/passage.
This exact thing happened to a friend of mine, and he ignored the oil light. The final oil change on that engine was an SM/CF rated synthetic, after years of mineral oils. This was a Toyota Sludge Monster, though.
I can appreciate Drew's words (and thanks Bill). My issue is the over emphasis on certain words, phrases and thoughts. A couple examples:

"Seal shrinkage" and "Seals swelling" always sounds so dramatic. When most well formulated oils won't turn Billy Barty into John Holmes, or visa versa....

"Synthetic cleaning" always sounds like the restroom at the annual Ex-Lax convention, completely blown out. When, IMHO, synthetic cleaning is quite gentle and natural.
Im about to switch over my fiance jetta either to syntec 0W30 or 5W40 since its got 65K with no oil leaks gental and natural cleaning sounds good to me.
Switched to M1 at 80k miles, no leaks, no burning. Of course I consider anything under 100k miles "low milage" so maybe thats why I didn't think twice.
I went to Synthetic at 118,000 miles, now with 171,000 miles on the clock, the engine is as clean as a whistle inside. It doesn't leak any oil, burn any oil, and runs better than new.
Went to synethetic at about 120k miles on my 87 Cutlass with small block V8, 3 years ago, even at that age and mileage the synthetic had no effect on it whatsover other than helping keep the thing running like new to over 200k miles with the hardcore use I gave it. :)

It is the ester that can cause problems when one changes from mineral to synthetic

If I understand right.. From what MolaKule has stated in the past. The additive package in most all current oils including dino oils is Ester based. So I do not understand this statement at all.
I did a lot of research concerning synthetics in college. Switching at 50,000 isn't totally advised, but can be done. Because of the viscosity, if theres a leak it'll leak twice as much. Same goes for use. If you drop a quart after say 3,000 miles you'll probably drop the quart faster. Best to do the switching relatively sooner in the engine's life.
And further, you don't have to worry about compatability. Synthetic's by far are better oils. Proven. The only problem is if you want to verify the switch because of $ really can't be done yet. You can extend the interval but I doubt if the warranty would hold up if there would ever be a problem. But the posts above are correct. Synthetic will preserve the life of the engine, no doubt.
Switched to Redline (ester synthetic) years ago, and sorry but I don't have any "synthetic horror stories" to tell! My engines last forever and a day!

I did also go through both a "Rotella" and "Mobil 1" phase back when, and was not particularly impressed by either.

I'll never run anything but Redline in my truck, and Maxima Extra (also ester synthetic) in my dirt bikes.

That's Billy Barty, on the left...

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