So your saying that Mercedes is wrong for setting the service interval so high. If they ran conventional oil in it, it would have gunked up past the point of being operation after the 3rd oil change.

Changing synthetic oil at 6000 to 7000 miles is too wasteful.

What benefits are there to synthetics if you are changing that often. I thought longer service life and higher boiling point. Changing at 6000 is like changing dino oil at 2000 miles. Sounds like money wasted.


And Somebody explain to me what flash point is because it really has nothing to do with the performance of oil. I could be wrong but I'd like to know.

Yep they are.
Manufacturers always use mobil 1 because it is available world wide and get it anywhere but it is not the best Synthetic, RedLine and Amsoil are considerably better oils but you can not get either one at Wallyworld or one some street corner in Belize.

Flash point is the temperature at which an oil gives off vapors that can be ignited with a flame held over the oil. The lower the flash point the greater tendancy for the oil to suffer vaporization loss at high temperatures and to burn off on hot cylinder walls and pistons. The flash point can be an indicator of the quality of the base stock used. The higher the flash point the better.

Flash point on 5W30 Amsoil is 478 degrees, ALL synthetics are above 410 I am pretty sure.
Most conventional oils are between 350-380 I think.

What breaks down motor oil is HEAT, the better oil can handle heat the longer it last and better it protects.
Petroleum oil is comprised of various sized molecules, some tiny some large, the tiny molecules are what burn off first, that leaves a high ash content in the oil which is what creates sludge.
In petroleum based oil this happens almost immediately, they start breaking down very quickly.
Synthetic oil does a much better job of cooling the engine, components within the engine usually run 15-30 degrees cooler than with petroleum.
Synthetic oil molecules are basically created all the same size so what little does burn off what is left is still the same characteristics it does not degrade nearly as fast as petroleum.

That fact is why I was sold on synthetic oil to begin with back in 1977 with my old Baja Bug, engine ran much cooler.

I usually change my Amsoil once a year which is usually around 8000ish miles for me but I wouldn't have a problem taking the Amsoil out to 10,000 or so especially if a few 1000 were highway miles, same with Redline which is another excellent oil.
Mobil 1 not so much, 7000 and its time to go, 13,000 on Mobil is quite a bit past where it should be.
If you want to take a synthetic to 13,000 or more then use Amsoil or Redline and a bypass filter because much past 8000-10,000 miles and you have to worry about the filter as much as the oil, even if your oil is still decent the filter probably wont be.
The Amsoil filters are quite good, so are the K&N oil filters but even though they are supposed to go up to 15,000 miles (Amsoil filter) I don't trust it past 10K.

Because my Diesel truck used so much oil was 9 Qts I think I had to use a bypass filter in it so i could take the oil to at least 8000 miles so I could warrant using the higher cost synthetic, because diesel dirties up oil rather quickly so need a really good filter to keep it clean. If not best to just use the Rotella and change it every 3000.

So your saying that anybody using conventional oil will have a ticking time bomb with potential explosive vapors.

Highly unlikely.

Yes - regular oil has a flash point of 392 and synthetics are higher at 450 but that has got nothing to do with the internal combustion engine. Oil temperatures seldom get higher then 240 degrees Fahrenheit. Even at the piston walls. I have torn down, many engines and i have never seen burnt oil on the cylinder walls. I have seen carboned up rings but that is a byproduct of combustion. If the Temp hit 392 degrees, catastrophic failure will occur.

They only area where a motor might see those temps are the turbos in blown motors. And only then, when the motor has just been turned off and the oil that is sitting in the turbo housing is absorbing all the residual heat from being run extremely hard. (Thus turbo timers)

So there again, flash point has nothing to do with the usefulness of oil in our engines.

Mind you, I use Synthetics where they are needed (Audi Bi-turbo) but for the 4runner. I plan on keeping it for a long time and I plan on changing the oil every 3k miles.




One other point. You said that synthetics stick to metal parts better. Haven't you been to the parts store and seen the LUCAS stack 3 gear demo box. It had a little crank handle on it. you turn the bottom gear and the top gear got a nice coat of oil on it. Vs the other synthetic oil, which you spin the bottom gear as hard as you can and the top gear doesn't get nearly the same amount of oil. Just an observation I had.

Don't think you are quite understanding the concept of what flash point means, doesn't mean its going to blow up.
Only about 10% if the gas burned gets used to move the car forward the other 90% gets turned into HEAT.
Gets pretty hot in any kind of engine not just a turbo. Hell even the damn water inside the engine is 200 freaking degrees. But I digress.

But in general a higher flash point means the oil is more stable across all temperature ranges thus does not degrade as quickly. Whether it gets over 350 degree is moot. Look at it this way, if you have a rope with a breaking strength of 480lbs Vs a rope with a breaking strength of 350lbs and you use that rope every day pulling 350lbs up & down for hours a day, what rope do you think is going to last longer? The one that is right at it breaking strength or the one that has another 130 lbs left in reserve?

Lucas is just thick, doesn't particularly adhere to metal better especially at high temps. I could put molasses in that same dohicky and I am sure it would climb right to the top like the Lucas does but i am not going to run it in my engine.

I can see you are pretty set in your opinion and so am I so probably not much point in continuing this.
I would suggest that you run your conventional oil and change it at 3K and I am sure everything will be fine.
I will run my synthetic to 8K and also everything will be fine.

Funny thing is it appears as though you accept that synthetic is is indeed better oil but basically that your 4runner doesn't really deserve it.

Whereas I believe even my pressure washers Briggs & Stratton deserves it.

synthetic is great but it is over kill in our 4runners, unless you are changing your oil every 10k.

The new Toyota Camary now requires Synthetic (0w-20w) and toyota's recommended service interval is 10,000 miles.

I'm pretty much with you up to here. But unfiltered seasonal homeowner-type single-cylinder engines need frequent changes much more than they need higher performing oil. I have an ancient fleet of B&S and Honda single cyls going up to 50 years old on B&S and twenty-five on Honda and I have never lost a 4-stroke engine with dino oil. I had one 1938 Homelite 2-stroke generator die (no oil to change--obviously). Change it every season and those motors really don't care. Now you're using 10-ton wire cable to lift a shoe box.

If I were a contractor with constant use, I'd go to syn, though.

No such thing as overkill with lubrication, it is the lifes blood of your engine.

About time Toyota started wising up, I guess a few billion dollars lost from the sludge problems woke them up. Although I think the 10,000 mile interval is a bit of a stretch though especially since 8 outa 10 owners will use Mobil 1.

I save money using synthetic changing it at 8k.
I wouldn't trust petroleum oil of any kind past 3K at the most.
In order to come close to the same protection I get with synthetic changed around 8K (1 Year) I would have to change my petroleum oil 3 times in that same year so I would spend MORE using petroleum and not get the benefits of using synthetic.

I do both since I only use it very infrequently once or twice a year at the most and it only takes such a small amount of oil it basically gets brand new synthetic (Mobil 1) probably every 5 hours of run time. The cost is nominal.

Aside from all the really long posts here, I usually use synthetic (I don't think I have switch the 4runner over yet, but probably will) just because the change interval is longer. I have a long commute, and put miles on pretty quickly, so I hit 3k miles pretty quick.

Here's another question about conventional vs syn oils. Is there really any problem with switching back from synthetic to conventional? I have always heard that there is.

Because that rope will only last a month or two instead of a year.

OK, Lucas is thick.
However if I wanted something really thick in my Diff I would use the 75W110 Amsoil but not sure what this has to do with anything.
I use the 75W90 Severe Gear Amsoil, works great.



Well I do get Nitrogen in my tires but its free at Costco.
The gains of using synthetic oil far outweigh the cost, in fact it is cheaper.

Nope there isn't any problem switching back & forth but I doubt that you will.
Especially if you put lots of miles on your 4runner quickly

Bottom line on this conversation between Nunyabiz and Singtoe:

Nunyabiz feels that his 4Runner deserves full synthetic. Singtoe feels his 4Runner works just fine with conventional. BOTH are correct...the problem is that everyone is trying to justify their feelings on this debate with numbers and fact and proof of this that or the other....when it's really all moot when each oil is used correctly.

Conventional oil, when changed regularly can easily lubricate and protect an engine for the life of the engine....and NOT be the cause of failure when the engine eventually dies or needs rebuilt. Some of the highest mileage engines in the world used conventional oil their whole life.


I just tore down a 100k mile engine that had used Quaker state conventional it's whole life, changed regularly. The engine and head look immaculate.



Synthetic is better. Conventional is plenty good enough. Its like playing a 3 man scramble in golf: yourself, Phil Mickelson and Dustin Johnson. Yes, Phil is better than Dustin...but Dustin works just peachy....cause he's still quite a bit better than necessary for playing the local tournament with amatuer golfers.

I've been using Motomaster Formula1 synthetic in all my vehicles for years now. It's made by Shell (as per MSDS sheet), it meets or exceeds GM's Corvette standards, for which Mobil1 is the factory fill, it is a full synthetic unlike Mobil1, and it goes on sale for as low as $16.99/4.4L jug. At that price, you get the benefit of synthetic, with the price of a quality dino-oil, it's a no brainer. I'm sure you guys in the US have a comparable option if you look around.

Sadly, it's not designed for diesel use, so I've been using Shell Rotella non-syn in the Surf, and I'll be doing 7500km intervals. Seems to be working just fine so far. I did use synthetic lubes for the diffs and transfer case when I changed them, and non-syn for the tranny when I did a few drain/fills.

All totally true

Nice analogy. Now you're speaking my language...