Mineral engine oil vs. sinthetic

[LM 25575]

Need to change oil in my '76 car. Engine had never been rebuilt (not lately at least). Someone told me would be better to put mineral oil in place of synthetic. Any opinion about? Thanks.

[Dave Shepherd]

Not knowing the engine's internal condition I would stick with mineral oil.

[TJ Hopland]

If you like / believe in synthetic use it.  If you believe synthetic is a superior lubricant then why would it not be a superior lubricant in an older engine?  The additive packages which include detergents tend to be the same between brands whether or not its synthetic or standard.   The blends are also pretty popular now if you are not 100% sold on synthetic or cant quite bring yourself to spend the extra money.  I have switched back and fourth between synthetic, blends, and regular oils over the years and have not seen any difference in leaks or consumption.  Leaky worn out engines still 'use' oil and the nice ones dont.         

If the engine is filthy inside any fresh oil is going to have similar detergents in it and will start cleaning stuff.  This is assuming you are not seeking out a non detergent oil which most commonly is only available in a SAE 30.  If the new oil gets dirty real fast I would change it again.  I have had cars that were so bad that I have changed the oil and filter 3 times over a 2 week span.  After that went to like 1000 miles and then finally to a normal 3000.  Oil now stays what I would consider normal for its age.     

[kgray39011]

If you are going to change to synthetic oil from mineral oil, you must be prepared to change the oil a couple of times quickly . As TJ Hopland mentioned it IS a superior oil , however it will clean EVERYTHING internally. You must watch your oil very close and be prepared to change the oil as it WILL desolve ALL the sludge and varnish off. It can and will clog your oil filter untill it is all cleaned up !!!! I did this with a ten year old car and had to change the oil before 500 miles and again at 1500 miles before it was cleaned enough to go 10,000 miles.

Mineral oils do break down much quicker. The synthetic oil has much more uniform molecules and a much higher heat rating. All turbo charged cars use only synthetic, as most newer performance cars.

[Dave Shepherd]

In other words if you have a sludged up engine Syn is really asking for trouble, no?

[The Tassie Devil(le)]

Yes.   Both Synthetic and Mineral Oils just don't mix.

I was always under the impression that if one is going to change to a Synthetic Oil from running Mineral Oil, one should strip the engine down, clean it all up and then reassemble and use the Synthetic from then on.

It is a bit like changing from Dot 3 Brake Fluid to Silicone Brake Fluid.   One has to completely remove all traces of the original, and even replace the flexible hoses and replace the cups and seals with Silicone-friendly parts.

Bruce.

[TJ Hopland]

Has anyone ever done any sort of test to see if the synthetics clean better?   I dont think I have ever noticed that claim in their advertising.  I have not seen anything that has made me think that the synthetics clean any more than regular.   I for sure would not add any sort of cleaner or engine flush to the oil if you have a very dirty engine, I would just let the detergents in the fresh oil do their thing and change it often.

I also dont understand what the issue is with mixing the oils?  If that was bad why do they sell blends?  Blends were even recommended by some manufactures. 

Another thought that may be adding confusion, I am assuming that mineral, organic, and regular are all the same thing.

[Mike Josephic CLC #3877]

In my opinion, switching to a synthetic in our "old cars" is just asking for trouble.

For a car driven infrequently and as many of ours are, just a few hundred miles per
year, there is no benefit.  It's a waste of money plus a synthetic put into a 50 year
old engine will loosen up much of accumulated crud that is in there.  Ant THAT is
something you don't need.

Stick with the oil the car was designed to use.

Mike

[The Tassie Devil(le)]

G'day TJ,

The thing about Synthetics in any engine that is currently using "normal" Oil, is that the Synthetic has the ability to dissolve the crud that gets built up in the nooks and crannies in a system.   When "lumps" dislodge, they can get distributed around the vital parts, especially Hydraulic Lifter internals, Bearing Shells, and depending on what is in the "lump", block, or damage parts.

Another thought that may be adding confusion, I am assuming that mineral, organic, and regular are all the same thing.

Yes, the same stuff.   Mineral is actually Organic, as it was organic, or animal, before the million year process of turning it into that black stuff that comes out of the ground.

Bruce.

[TJ Hopland]

Just curious what makes synthetics a better cleaner than regular oils?  I have never heard that before, I took a quick look at a few of the popular brands sites and their claims of their cleaning properties appear to be identical for their regular and synthetic products, they all even all now have a high miles or extended performance product that really has no specific information that I can find in how it differs from their standard product other than its 'specially formulated'.  Its possible I missed something but if they were better cleaners you would think they would hype it along with the other benefits they claim.   I get how the synthetic is more pure to start with and therefore less prone to breakdown not to mention not putting extra crap in your engine in the first place but dont see why it would tend to clean more than any other modern oil meeting the same minimum spec. 

[Mike Josephic CLC #3877]

TJ:

There are numerous references to this question on the net. Here's just one:

http://www.pennzoil.com/#/motor-oil/pennzoil-ultra

The producers DO tout the "superior cleaning ability" of synthetics.

Mike

[dadscad]

Here is the Amsoil "FAQ" response about installing synthetic oil.

Will synthetic motor oil clean the sludge from my engine and plug the oil filter and passageways?
Answer: Absolutely not. Switching from petroleum oil to AMSOIL in routinely maintained vehicles will not cause clogged oil filters or passageways, regardless of mileage. Sludge, which is caused by poor quality oil and neglected maintenance practices, would have to be present in significant amounts to plug oil filters and passageways. If this excessive amount of sludge is present in an engine, it is just a matter of time before oil filters and passageways clog, regardless of the installation of AMSOIL.

Amsoil synthetic oil is suitable for use in any engine that is in sound mechanical condition.  http://www.amsoil.com/frequent.aspx

FAQ response about mixing Amsoil synthetic and mineral oil.

Are AMSOIL synthetic motor oils and petroleum motor oils compatible?
AMSOIL synthetic motor oils are fully compatible with all petroleum motor oils, and there is no danger in mixing the two. Mixing AMSOIL and petroleum oil, however, is not recommended as a general practice. Performance and long drain intervals will be sacrificed and the oil should be promptly changed, at maximum, within the next 3,000 miles.

Synthetic oil flows quicker on cold start ups, getting to vital engine parts quicker than conventional oils. This fact alone makes it a better choice for infrequently driven cars. The engine that sits for weeks/months allows the lube oil to drain away which will create excessive wear on start up until the lube oil is circulated through out the engine. Synthetic lubes do circulate quicker, helping to prevent engine wear on start up. For years, I have used synthetic oil in my daily drivers and in my 63 CDV. Personally speaking, I think, synthetic lubricants are far superior to refined petroleum in every way.

[TJ Hopland]

Looks like all Pennzoils products clean better than others, at least according to them. 

The FAQ's of all the brands are almost identical.   

[LM 25575]

Can we really totally trust a producer's FAQ's? AMSOIL  says mineral can be blended with synthetic. But little after says that it is not raccomended as general practice....So, can be blended or not?  (Or maybe it is just my poor english which doesnt' make me understand correctly?)

[TJ Hopland]

They all say the same thing about blending.  They say there is no harm in it but they dont recommend it because by mixing their 'superior' oil with an 'inferior' one you loose some or all of the benefits of their superior oil leaving you with the qualities of the inferior one.   Assuming the inferior oil meets minimum standards you should at least be as well off as you were to start with but with at least a little of the good stuff in the mix you may be slightly ahead, assuming you believe in synthetics in the first place.

Go look at any of the sites, they all have a FAQ and Myth section and they are all almost identical.    

[Art Woody]

1 qt. inferior oil plus 4qts. superior oil equals 5 qts. inferior oil. I changed to syn. oil in my 12 yr. old motorcycle to reduce transmission whine at 55 mph. I got a quiet transmission, super smooth shifting immediately and picked up a solid 2 mpgs. I said 2 mpgs. on a 1530 cc engine. Art Woody

[John Tozer #7946]

So gents,

If you had stripped down and rebuilt a 346 flathead, would you run mineral or synthetic in it?

John Tozer
#7946

[kgray39011]

Synthetic oil is superior oil, period. The molecules are much more uniform in size, it can handle higher tempertures, flows better when cold, does not sludge up, stays cleaner....the question is are you willing to pay $7 vs $2 a quart and you are going to go 10,000 miles between oil changes, it makes sense for a daily driver, but for your classic that sees a couple thousand miles a year, would you go 5 years between oil changes?

[Dave Shepherd]

Using modern internal parts, yes.  After the requisite brake in period.  Isn't the op's issue here whether to use syn oil in engine with unkown internal condition.

[The Tassie Devil(le)]

So gents,     If you had stripped down and rebuilt a 346 flathead, would you run mineral or synthetic in it?   John Tozer  #7946

Yes, but what sort of "Pre-Lube" would one use to lube the Bearings, Lifters and Cam Lobes so that the Breaking-in of the Lobes wouldn't be compromised?   At the moment, I use a Pro-Mar product.

Bruce.