New member here.
I'm really surprised (been big time backyard mechanic for 40 years) and a bit confused reading the majority of posts stating folks changing synthetic fluids so frequently. I have always (since it became available) broken in my vehicles with standard lubes and change schedule, then switched to full synthetics but also switched my change-out schedule from every 3000 to every 10k unless a lot of heavy work, then every 7k.
Why do so many people change their synthetics (so much more expensive) at non-synthetic change intervals? I have a cousin who is a chemical engineer, actually works for an oil company, and he discussed this with me in great detail (much more than my brain could soak up) how vehicle fluids work, especially the synthetics, and he said that the latest synthetics over the last 10 yrs especially, do not break down like regular fluids, nor create and leave near the amount of carbon that they do, and this is why synthetics are so good except before a good break-in is performed. According to him, the newest (from natural gas) doesnt begin to break down or degrade until around 60k miles with normal driving conditions.
So I'm just curious as to why people would pay 4x the $$ to change fluids at the same, or slightly longer, mileage intervals. Maybe I can learn something new here.

 

Oh, and to add a bit.... I know that carbon is actually a good thing in an engine, as it actually does a good job of lubricating moving parts. So the real problem is that the carbon can start becoming a "sludge" that blocks up the filter, and smaller holes and tubes that circulate it. I still replace my oil filter with each change, although my cousin (and several friends of mine) swap out their filters every other change, one every third change. Their view is that filters do not clog that fast, especially for those that change fluids per schedule or sooner, and is just a waste of money. As I said, I replace mine every other change, and have had every vehicle I've owned (knock on wood) last at least 175k up to 220k and were still running strong with no problems (eating oil, etc.) before trading in or selling. And my '77 K10 was also done this way (Original owner kept and gave me EVERY receipt for every single thing he did) and is running strong with 650k on it. I'd think if my way of doing it was detrimental, I would not be getting such long life in my vehicles for so long.
But I am an info addict, always open to ideas, and cant learn enough, so all *respectful* disagreement and ideas always welcome.
Thanks folks, loving the site!

 

Many of us here like our trucks, so we (I) get paranoid when the oil gets dirty on the dip stick.
I don't use synthetic, but maybe after my engine breaks in.

After the engine is broken in, how long does it take for the synthetic to show dirty oil on the dip stick ?
I was under the impression oil became dirty from burning dirty fossil fuels.
That's where the carbon comes from ???

 

Firstly, I am an old "backyard" mechanic, which actually meant something until computers and such came into the picture, now it damn near takes a computer geek to figure much of it out. That said, yes, much of the carbon comes from the burning of carbon based fuels. But when traditional lubes begin to break down, they begin "burning" themselves, thus the burnt smell I was trained to check for when looking at a vehicle.
Since I started using synthetics, I noticed that the oil at even double the normal interval would remain a dark honey color and have yet (even with very dark synthetic) has never had that strong burned smell as non-synthetics. My 80yr old Mother who forgets easily anymore had me change her oil on my last visit, and had forgotten about changing and the sticker in the window indicated she had not had an oil change for 63k miles (2002 Honda Civic), and I was expecting black on the dipstick. I was very surprised that it was like a light molasses or very dark honey even at that interval. Mobil 1 was the oil.
But it really reinforced my belief that what I've been told is true, that full synthetics really do hold up for many many miles.
Just fyi, I replace my oil filter every other change. My "know it all" father in law told me that my new oil would turn black right away because I was using the old filter... Wrong.. LOL! I ran it for 2 days, then had him pull my dipstick. Maybe SLIGHTLY darker than fresh oil, but still golden colored.He lost the smug look pretty quickly and since switches his every other change. But he was still using standard oil, and his DID turn black in a couple days, thus he started using synthetics after that (Amsoil? which I know squat about) but said he now had clean oil even re-using the oil filter.
Hope that helps...

 

What about older engines from an era before synthetic wasn't even thought of, would they be suitable for synthetic oil ?

Lets say you took a Rolls Royce Silver Shadow from 1975 that required 20/50 (or so the owners manual says to use)
Or even an earlier RR with their F Head inline six, the factory also list 20/50 for that too _ quite thick.

In those day, tolerances and machining practices were not as tight, or so I've been told and there for a thicker oil was needed to take up larger spaces in the mains and rods.

We're still talking about 1 or 2 thou difference, or maybe less compared to a modern engine.

Why would Rolls Royce list 20/50 oil _ don't know what the new BMW engines list ???

I've never compared 20/50 full synthetic to conventional oil, but I've read that it's quite a bit thinner even though it's still rated at 20/50, why is that and would it be suitable for an older engine with original miles on it (not rebuilt to todays standards) ?

And for the record, even though I could probably keep the same filter in there, I would change it anyway, it's like 7 bucks....

Here's a theory about why synthetic oil stays cleaner longer.
The molecules of oil in synthetic are much smaller then standard oil, those molecules are also all the same size as apposed to regular oil which are all different sizes.

Carbon from burning fossil fuels enters the oil pan from blow-by in the combustion chamber upon compression and exhaust.
I say exhaust too, because even though the exhaust valve is open, some crank case blow-by still occurs, even on a tight engine.
With conventional oil, because the molecules of oil are all different sizes, there are larger spaces for the carbon to get by and enter the oil pan area, thus contaminating the oil with carbon.

With synthetic, because the molecules are all the same size (so I've read) the smaller molecules are allowed to be come more tightly packed and this helps to prevent carbon from entering the oil pan.
In other words, the larger particles of carbon (still talking about microscopic bits here) have a more difficult time getting past the smaller molecules of oil in the synthetic.


On the other hand synthetics break down at a much higher temperature, compared to standard oil. Standard oil brakes down at around 240F, quite far above the boiling point of water. (212 degrees F.)
So if standard oil is breaking down at 240 degrees, why would it turn to carbon if an engine is only running near the boiling point ?

If what you're saying is true about conventional motor oil breaking down is true, then the engine in my 51 Bentley should be a carboned up mess.
It's been at least 15 years since it had a total rebuild and there are no traces in the valve train of the familiar yellowish carbon build up from conventional motor oils _ no varnish at all _ the aluminum, brass and steel all look their natural colours.

However that engine has been looked after and has received regular oil changes, even though it gets driven hard it still remains internally clean.

So why does conventional motor oil appear to become dirty faster, I think it's because of my theory, not because it has a tendency to break down at a higher rate when compared to synthetics.

Or maybe a I'm wrong, even though the coolant in an engine may operate near the boiling point of water (or even above with a pressurized system), the oil is running much hotter at around 240 degrees.
Maybe that's why my Bentley is internally quite clean, it's red line is 4200 rpm, and it's cooling system is not pressurized. (its rad is huge)
The engine itself is just not working (or revving if you like) as much as a modern engine and that keeps the oil from breaking down.

 

@CJ60: I am new to the synthetic oil club. Have always used Pennzoil for my vehicles... until my last oil change. I went with a synthetic blend oil and a new Motorcraft filter purchased at Rural King. I will be watching it to see how it looks on the stick at 3K miles and make my determination based on what I see. I am "old school" and the 3000 mile oil change interval is buried pretty deep in my head! :)

BTW: the oil and filter cost me a whopping $11.98!

 

Synthetic oil is capable of going 10K+ without any issues. The filter is now the weak link in the system. The anti-drainback design is good at screening out abrasives, such as carbon, dust, and bits of metal but they do load up. I will not run a filter more than 5k miles. If you cut one open you can see how much grunge and crap it does filter out. It is also a good read for any metal that could cause failure.

 

@Tsquare: So basically, you are saying that if running synthetic oil 10K, you would change the filter at 5K and top off the oil? That makes sense I suppose. Just curious; what brand filter do you use? I normally use a Bosch filter, but I went Motorcraft this time. I feel confident the Motorcraft is plenty good since Ford designed it.

 

Synthetic is less about how clean the oil is. It breaks down slower and maintains its viscosity longer. You can't judge am oil by looking at the dipstick. If you tried that with a diesel you'd be changing the oil daily...

I change the oil in my ranger at 5k intervals. But I don't idle it very long and drive it almost exclusively on the freeway.

 

We talk about oil breaking down and losing its viscosity...
What happens to all the used oil at the recycling centre ?
I was told that it simply gets filtered, cleaned and re-used.

If that's the case, it doesn't actually break down, but simply gets dirty ???

 

MHoward, I am using Motorcraft - OEM works every time. The AC Delco is one of the best filters and usually does not cost that much more than Motorcraft. I just can't bring myself to put GM parts on a Ford...

 

Used motor oil goes through a refining process after it is filtered to get the metal and dirt out of it. It does break down but the refining process yields a lot more coke and solid by-products.

 

https://auto.howstuffworks.com/thermal-breakdown.htm

 

So it's not a question about how hot an engine gets, it's about how refined an oil is.
The more refined (distilled) the better it stands up to the given heat of an engine.

An engine can only get so hot before the fuel evaporates before it can be fired in the engine.
Plus, metals in the engine expand, gall and bind when an engine runs too hot, or when the driver insists upon getting home when all the coolant leaks out of the rad.

Engine damage will occur long before the break down of oils in an engine that runs to hot and over heats.

There must be a pretty fine line to all of this.
More then 90% of engine wear occurs on cold start up _ an engine that's fully warmed up wears the least amount.
There must be an optimal temperature where the oil lasts the longest and causes the least amount of wear to the engine.


EDIT:
Here we go, this makes sense.

http://www.hotrod.com/articles/engine-oil-temperature/

 

I may run synthetic in my truck, but up here in Canada, it would be quite expensive to run in my Bentley.
A 4 litre jug runs around 35 to 60 bucks, Royal Purple being the most expensive.
The Bentley takes around 15 litres of oil.

If what they say is true and it probably is, then I should save money, even using it in the Bentley.

 

Dyno oil will get dirtier in part due to it's own impurities, it's been mentioned already about how refined it is.

One thing i will say is that you cannot reliably judge oil suitability by looking at the dipstick anymore - if you're truly interested in extending the oil change interval, you need to be sure that not only your motor, but driving style/tendencies will suit it.

The only way to find this out is by UOA testing - used oil analysis.

I've used Blackstone Labs many times with good success, costs about $25 a pop, i do it on most of my engines a couple of times to make sure they're healthy, but won't typically do it again unless i think something is going wrong or has changed.

Kit's are free (got a handful in the garage) and i do recommend them if you care about longer life of your engine.

https://www.blackstone-labs.com/

 

So what are the results of your tests and what vehicles ?

Interesting...

EDIT:
It's like looking at a blood test...

https://www.blackstone-labs.com/gas-...e-report-1.php

 

Great post. Oil analysis is second nature in the diesel world.

If someone is really worried about oil temp install an oil cooler. On my diesel coolant and oil are never more than 6 degrees apart.

 

Synthetic oil is like lifetime coolant, great to use if you never gets leaks, then it gets expensive, lol.

Any older vehicles get more leaks and broken hoses and more Blow-by
So in my older cars/trucks I use regular oil, name brand but cheaper, and 2 year coolant

Synthetic is a good idea for most newer vehicles, and not that much more
Quart of Quaker State 5w30 is $4
Mobile 1 5w30 is $7.50 BUT, you can get 5 quart bottle for $23 on sale, so $4.60 a quart

I like Quaker State it has served me well over the last 40 years, so I can't argue about "better" brands, lol, well won't argue
I change this oil/filter every 5k not 3k

I have used Mobile One, almost since it came out, in engines that don't leak oil, and have no complaints
I do change the filter every 5k and add/top up with more synthetic, and I really don't change this oil for maybe 20-30k, just change the filter

My 1994 4.0l is close to 400k now living on Quaker State and 2 year anti-freeze


Oil is used to cool and lubricate, it has a high vapor point and almost nonexistent freezing point.
You could use water but it would turn to steam on hot bearings and would rust parts, lol.

 

Question for you oil gurus...What filters should we be running for synthetics? The typical Fram and even Motorcraft oil filters aren't designed for synthetics. The upper end Fram's say they'll work but what other filters should we be looking at?

I know my '08 Mustang (4.6 3v) as well as the '11 Ranger both recommend Motorcraft synthetic blend. So the Motorcraft filter should hold up to the blends but what about full synthetics?

 

Horses for courses....


*Generally* running fully synth in an older engine can cause issues*

*I mean it will burn more.


All engines, even of the same type, are different. My personal preference is Penzoil, bang-for-buck. I also like Castrol, but only run that in my bike.


For example, my 350z doesn't like synthetic oil, even though it's newer and had less than 100k miles, i ran Castrol Edge in it, but that burnt visibly from the exhaust sometimes when it was really hot.

5w30 - it's a definition of the oils viscosity in two different temperature tests - how "runny" when cold and how "runny" when "hot"
It needs to be noted that those ratings have brackets, my example here is that a 5w30 in Castrol Edge is one of the 'thinnest' oils in the 5w30 range.


Anyway, to sum up a point a few people made earlier, within the same rating of oil, there are different viscosities, there are also changes in the same rating between the 'types' of the same brand, for example, dino (conventional) oil, blend, or semi synth, and fully synth. The more uniform molecules in the oil as it goes from dino to synthetic can allow more 'seepage' past oil seals, rings etc.

As a result of the above, my 350 only likes Penzoil yellow bottle, or Catrol GTX (each brands conventional oil) And that's fine, it's used oil analysis comes back thumbs up from using it.

My Wife's TSX (year newer) likes Penzoil Platinum just fine, Platinum is Penzoils "synthetic" solution (don't ask or get started on the American lawsuit about what can be called synthetic) Penzoil Platinum Ultra is their top range synthetic, the only difference is more additives (cleaning/conditioners/etc)

Anyway, i have attached one of the my 350z UOA's, just as an example, honestly, one of the things they (Blackstone) can advise on is if the important parts of the oil are still in play (ie. can you run it for longer before changing) so things like it's cold/hot viscosities - are they still in spec, the additives - how many are left, how much metal is in the sample - is your engine grinding itself up?

 

Meh, it's BS, the short version is you just need a good filter.

I've always run Motorcrafts on my Fords, they're fine for that and very cheap.

Several years ago, Purolators were the "go-to" filters, but they redesigned them and the quality has gone down hill, not recommended anymore.

Many many years ago, Fram were a great filter, then they spent most of the 2000's being nasty crap you shouldn't touch with a barge pole, let alone your engine. In the last couple of years, they got sick of the bad rep they got, and redesigned it all, now, the best filter is the Fram Ultraguard, or the Toughguard (one level down) are classed as fine filters.

Bosch filters are fine, i believe the Royal Purple and K&N filters (oil) are also fine, but both unnecessarily expensive.

 

Good info, I'll keep that in mind.

I've used Purolator and Fram over the last 10 years but even with synthetic, I've always changed all my vehicles at around 5K miles. The Mustang gets an oil change a year, and that's only on 2,500 miles or less.

 

Yup, time is a factor (how long it sits there with the blowby chemicals) as it will slowly get more acidic over time.

The more a vehicle idles, or frequent start/stops (stop lights and signs etc) the harder it is on the oil, it's why American has 3000 miles as "normal" (it's actually the manufacturers 'severe conditions' spec (Vs 5000) of course there are many newer vehicles that have much longer manufacture based change specs but they're another story for us with Rangers and older vehicles.

Anyway, it's how varied all that can be that makes the UOA's very useful for working out when you really *need* to change oil, instead of a generic assumption change period.

You can see an example of this in the summary for my 350 i posted above - i get the same averages of vehicles with another 1000+ miles on the oil, meaning i can go further before changing.
You can signify what you're getting the UOA for when you submit it and they tailor the analysis response to that.

 

Wonder where the OP is ?
This thread is going to go like so many threads _ pages and pages of oil discussion...