Why use a 30W synthetic?

[GlennT]

I've discovered that Amsoil seems to be the only company that sells a straight 30W synthetic oil. Why? Under what conditions would you use a straight 30W synthetic? Wouldn't the additives that produce a multigrade oil be kind of a bonus? I've followed the oil discussions on this forum for years and don't ever remember any mention of this.

 

[littlediesel]

Very thought provoking!!

I have thought about this subject for some time now regarding the use of the AMSOIL 30W synthetic oil. In conclusion, I have just switched to it. My reasons were as follows:

Many old time mechanics will always advocate for a 30W oil. They claim that a 30W oil is better than any multigrade oil. These multigrade oils were only developed for the convenience of temperature ranges that most vehicles will experience across their respective demographics. It would not be practical to change oil to a different weight as the temperatures change. Therefore we had the invention of the multigrade oil.

If synthetics are more stable to temperture, then would this serve as the same effect as a mutigrade oil? This is what I have experienced. I live in the cold northeast and my engines start very good in the cold weather with AMSOIL 30W.

I was never a strong advocate of multigrade oils. For years I used conventional 30W in my vehicles for the 3 seasons and used 20W in the winter time. Until recently, I switched to AMSOIL 30W synthetic year round.

Also, why does a small air cooled engine last much longer using a 30W oil than a multigrade oil? To me, this says alot about multigrade oils that they break down very easily and don't provide adequate protection. I believe this analogy also applies to large gasoline or diesel engines.

Any thoughts?

Jon

 

[art]

For me I like a straight weight in farm tractors that see constant load and full throttle. I have seen the multi weights break down in viscosity under non normal or full throttle auto use. I do vary a little for the winter as that is a time of only partial load use under normal conditions. I don't feel there is to much need to go to the synthetics as the average of 100 hours for an oil change or per season tells me the additional cost is not needed as any oil used will need to be changed before it is worn out unless higher hours of use are needed.

 

[geneP]

It was explained to me that multi weight oils use "polymers" to vary the viscosity acording to temperature. The polymers displace oil, so a smaller spread in the viscosity of multi grade oils is better, ie: 10w30 is preferred over 10w40 for lubricating qualities. Once an engine is up to temperature, a single weight oil (dino) will give better lubrication.

Newer auto engines are built to tight specifications, and specify lighter oils to get the oils to the engine parts faster on startup, reducing wear.

I'm no engineer of any kind, so take this as an opinion.

 

[pruntyc]

I worked for a man, that worked for the oil companys for years. And he said that when 30 weight got hot, it was thiner than 10 weight. But when 10-30 got hot, it stayed at the 10 weight. But gave the protection of 30 weight. So straight 30 weight would be like 5 or less weight oil hot. And that was why the mult-weight oils, not for weather changes.

 

[cpicton1]

Here is a link to a page that tries to explain how multi-weight oil works.
<A target="_blank" HREF=http://www.howstuffworks.com/question164.htm>http://www.howstuffworks.com/question164.htm</A>

 

[pruntyc]

That is basicly what I said, maybe he said it in more detail, but it comes out the same.

 

[RalphVa]

I was a chemical engineer and worked on processes that made lubricating oil base stocks for 31 years. A 10w30 oil has 10w characteristics (e.g. the viscosity range defining that weight) at low temperatures and 30w characteristics at high temperature.

I can't see why anyone would buy a single grade synthetic. It doesn't make sense. Synthetics were mainly attactive because you could get something like a 0w30 or 5w40 or 15w50 WITHOUT additives, or hardly any. Yes, it's the additives or combination of additives working with chemicals in the oil itself that either cause the oil to break down with time or to gel with time (can do either, depending on the oil, additive, etc.)

Synthetics are really great for air cooled engines, because they run hotter and will thus cause a conventional oil to degrade quicker.

They're also very good for engines with overhead valve systems, to get the oil flowing to that valve system as quickly as possible, particularly under fast idle/startup conditions.

My company did some research on engines starting at -40. The overhead valve system on those engines would start smoking from lack of lubrication if the oil in the engine was not a 0wxxx. About the only oil at that time availble in 0wxxx was a synthetic.

Most engine damage occurs at startup. It makes A LOT of sense to have an oil with low vis characteristics at the cold startup conditions but have a higher vis at higher temperatures. Doubt you need much higher than 30w at high temperature, but most diesels could probably benefit by having 40w at higher temperatures because they put more load on the bearings to "squish" the oil out.

Ralph

 

[BobCorazza]

Oil viscosity discussions always seem to get complicated /forums/images/graemlins/grin.gif
I looked at the 'how stuff works' link and noted a glaring error (at least from what I have read elswhere). The second number in a multi-viscosity oil is the oil's viscosity at 212 deg f. So 0w30, 5w30, ans 10w30 oils are all 30 weight oils. The first number (0w,5w,10w etc) is not a viscosity reference, but a relative number indicating how easily an engine will turn over in colder temperatures (the "w" is for winter). The 2 tests are entirely different. For petroleum based multi-viscosity oils, low "w" rating and high viscosity rating (ie:0w30) is achieved through additives. In the 0w30 example, pour point depressants are added to a 20 weight base oil to meet the "0w" cranking rating. Long chain polymers (viscosity index improvers) are added to 'unwind' as temperature increases to maintain a 30 weight viscosity. Oil additives break down, and that's where petroleum based multi-viscosity oils loose their lubricating quality. The wider the numbers (ie:0w40) the more stuff that has to be added. Anyway, synthetic based oils either do not need VI improvers and pour point depressants, or use significantly less for the wider spread multiviscosity oils. I personally would not use straight 30 petroleum or synthetic based oil in a winter application, because the first couple minutes of an engine running is when it is getting significant wear.

 

[KubotaBling]

what i said why have a 30w when u can use a 0w30 and works the same yet less wear at startup.. a 30w synthetic is a silly idea only amsoil would come up with.. cause there base oils will crumble and crud up cause they can't make a good 0w 5w 30 weight oil