Since we are on the topic of oil
 

Can someone answer this question? Is it true that once you switch to synthetic oil, its harmfull to go back to non synthetic? or is that a myth? I've heard that said so many times, but was never really sure of its validity??

AFAIK it's a myth

Jackd,

I agree with much of what you say as an engineer and mb driver.

Yes, absolutely ppl have had great life to the M103 engines, M117/119's etc... If the oil was changed regularly. How many more miles can I get to a M103 lower end when on dino oil it can see 500,000 miles????

On the other note- you are very incorrect on viscosity. ie 10W30. This is kinematic viscosity which has very little to due with how the cold pumping properties of an oil is- by definition it IS a dynamic fluid property. 90+% of wear occurs before the engine is up to temperature, and getting the oil there quicker should make some difference on startup.

Mobil 15W50 syn has similar thicksotropic properties as a conventional dino 5W30. So, I don't have to worry about seasons and oil changes as much. Ever start a car in -30c-40c??

I use to be a 3k oil changer... Now I do 5k with synthetic except for my TDI which goes 7-8 k. Which brings a point about oil.

You need to be using an oil which meets the manufacture requirements- so for Mercedes , regardless of year, it is Sheet 229.1 or 229.3 or 229.5 .

On the cleanliness note and long oil changes. in the early 90's I worked on many cars. I did valve jobs on several AMSOIL engines. They were not clean inside- I was not impressed, but realize that products have changed/improved.

Will synthetic oil and antifreeze still turn to jello??? I saw it in a Alfa which blew a headgasket and was driven very hot.

Michael

If not jello, mayonaise. Neither is exactly a lubricant! Synthetic will dissolve consideralby more water, but not THAT much!

Peter

I got to admit it was a severe case =0)

But you didn't spend the time with the steam cleaner trying to get the snoot out of the block.


Wasn't fun...

Was noticeably more thickened than any dino-headgasket case I've repaired. Still remember it today. But I have never heard many other ppl discuss this issue with synthetics.

Michael

You probably wouldn't have had to repair it if it was dino oil -- shredded bearings and wiped out cylinder walls.

I've seen what happens when someone fills the crankcase with undiluted antfreeze instead of oil (simple case of grabbing the wrong gallon container, I think -- probably being blind drunk too, I didn't ask!). Not much left.

I shudder to think of what sort of trouble that particular mix cause. Given the chemical nature of the synthetic base, it will disperse quite a bit of water and glycol. Don't know how much, and I certainly don't want to find out by leaking a bunch into the crankcase on any of MY vehicles, either!

Dino oil will simply separate when the detergent is overwhelmed, and circulate slugs of oil and coolant through the block. Not long -- the coolant will take care of the bearings pretty fast. Not exactly lubricant.

Peter

After reading all of the replies to this discussion I just might try Mobil1 to see for myself if there is a performance and, more importantly, gas mileage increase by using it. I have always, and will continue to, change my oil at the 5,000 mile mark. I remember when I was younger that most all car makers had a 3,000 - 7,000 mile window, depending on severity of service, ie stop and go city driving vs highway. Since I do some of both, but more highway miles, 5,000 is right down the middle and easy to track.

On a similar note, I've had folks tell me I was crazy to run premium gas, even on an old beater truck. All I know is that with premium I got better mileage, the various cars performed better, and I had a much longer interval between needing new spark plugs. One car, an '80 Chevette, bought with 32k on it, new plugs installed and the same plugs were in it when I sold it having 150k, and those plugs were not eroded down and were clean as a whistle.

Concerning some of the other comments I read, and don't get me wrong, I'm not meaning to start a war or anything, I'm not a rocket scientist by any means but I do remember reading an article in an automotive magazine a couple of years ago about Slick50 and other similar products. This article stated that teflon will bond to metal only after it reaches a temperature much higher than found in most engines. Simply put, it doesn't work because the engines don't get hot enough for the teflon to melt.

I have to agree with those who said that car makers, racers, etc will promote the product of the highest bidder. That is just reality there, we all have done that in one form or another, ie go to work for the company that offered the better pay and benefit package for the same job.

My .02 cents worth

samian4: re Viscosity: I was replying to this comment made earlier:
"I can let my 420sel sit for 3-4 hours and then check the oil. The oil will register lower and sometimes give you the impression you are low on oil. I can start the car up and drive it for about 30 minutes and come back in and check the oil. The level will be on the full mark."
It implied that synthetic oil was staying up in the engine instead of draining back down to the oil pan as any oil would do. My comment was a 10W30 is a 10W30 , synthetic or mineral. Flow is the same at equal normal engine temperature. I agree with your comment on cold pumping.
JackD

Switched both my diesels at over 100k to Mobil 1. They both leaked after a while. However within 5k miles of making the switch, the leaks went away.

Marshall Booth has run a test where he has determined that chain wear is almost eliminated with Mobil 1.

I believe that if you want to look for a quanatative visual quick gratafication when switching to Mobil 1, I would visually check the clarity of the Oil vs. using Dino. If you notice your Dino fill turning torward black at 4K vs. 7K. Then your Mobil 1 may have cost benifits. I own 4 engines and get different results. Why I don't know. EX: I have a riding tractor with a 1979 B&S 16 HP 4 stroke, I use it all year round for cutting grass & snow removal. I always used Dino 10W30 and would change to 5W 30 during the winter. I never considered putting expensive syn. in an old tractor. I decided to switch to Mobil 1 5W30 after one paticular cold winter to help with starting. This was recommended in the owners manual as an option. To my suprise the oil stayed clear for 2 years. I changed the oil because of age. The Dino dis-colored in 6 months. I have no explanation for this. Granted it's not an auto engine. Conversly my 2.0 Mitsubishi turbo charged engine oil gets ugly after 3k with syn or dino, I still use syn for other reasons. In my Mitsubishi 2.5 V6 I can get 6K vs. 4K on dino, so it's about a break even cost factor and I only have to change twice a year, so I go Syn. I had a used 88 Buick V6 that was a no brainer, strickly Dino oil. It rusted out at 115K, the engine ran great, I donated it to charity.

I have Dino in the newly aquired 91 300E but I will try Syn and see how long I can go before seeing a need to change the oil. I will then determine If using 0w40 Mobil 1 will make sense or not in a 13 year old car with a 125 k miles on it. If I go 7K between changes and only have to change 2x a year and get cold cranking power during sever winters it may be worth it.

I have yet to notice any significant gas milaege improvements.

The point is Todays Dino oil changed every 3K may be just fine for most applications, but in some cases there may be benifits with Mobil 1. Also, some people may just want the very best for their beloved cars and thats ok too.

Stubman: the color of an engine oil, after use, is not a quality criteria. I would be extremely uncomfortable seeing a quite clean 10,000mi old oil and much more comfortable seeing a dirty, almost black 5,000mi old engine oil.
Upon a lab. analysis, you would discover that the dirty oil contains a lot of contaminant, while the clean oil has very little contaminant in it. That would mean the clean oil does not have the same cleansing properties and/or the same property to keep the contaminant in suspension within the oil.
All lubricants contain detergents and dispersant additives, in various concentration. Less detergent and dispersant means that the contaminant remain in the engine, thus a cleaner oil.
I'd rather see my engine bath in a dirty black 5,000mi old oil than in a 10,000mi. old clean oil. It mean the oil is doing its job of cleaning the inside of the engine and keeping contaminant in suspension, instead of depositing those on engine parts.
JackD

I have changed the oil, Mobil 15w50 or 0w40, in my 300CE maybe 6 times at roughly 2500 mile intervals and each time it is dark and dirty. I just did my first oil change in a newly acquired 1990 LS400 after about 2500 miles and I was mildly shocked to see pretty clean oil. The previous change was done at the dealer and I don't believe that the oil was synthetic. It had a definite reddish color to it. I replaced it with Mobil 1 5w30. We'll see how it looks at the next change.

glenmore
1991 300CE
1990 LS400

A funny little sidenote to the current debate...

While surfing www.boatnerd.com today I spotted mention of one of the old Great Lakes vessels which had been down for repairs. During an engine inspection they found one of the wrist pin keepers broken and minimal damage to the cylinder. Their reasoning for the minimal damage...the swap to Mobil 1 sythetic.

Did you see that one Warren????

Mike:

As I said, Mobil 1 (and any other full synthetic polyol or polyether base oil) is a vastly superior lubricant by any lubricating quality measure, often by an order of magnitude. The most common measurements are squeeze-out (the pressure required to squish the oil out from between two steel plates), antifriction (friction reduction or slipperiness), galling resistance (the pressure that can be applied to a round "ball bearing" being slid without rotating across a standarized steel plate without marring the surface), and so forth.

I'm not surprised that Mobil 1 protected the cylinder wall against damage, the stuff is incredible. I use it at work to increase the life of some peristatic pumps we use -- very old design (1968 or so), and with the Mobil 1 the life of the pressure rails is months instead of weeks -- if I can get the techs to keep them lubed, they run for years instead of having to replace them every six months. Only change is Mobil 1 15W50 instead of the manufacturer's recommended oil and STP on the rolling surface. Great stuff.

Whether or not you come out cash ahead in normal operations is a different question, and I get kinda tired of the complaint that it's "not cost effective" and the implication that synthetics aren't better lubricants. They may not be cheaper to use, but they ARE better, in any application you wish to use them. You may not save any money short term, but you get much less wear.

Peter

i didn't even think to cite my avlubes.

piston engine aircraft lubricants...virtually all mineral oil basestocks.

i shall say it again, dino rules.