Switched to Synthetic, want to switch back...

[Panzer82]

A 280SL owner and SL Market Letter subscriber called me today asking about oil for his 280SL...

An oil change or two ago (he changes just once a year due to low usage, like most Pagoda SL owners I would guess) the shop he takes his car to recommended that he switch over to synthetic oil, so he did.

He's done more research and has learned that there is really no benefit to synthtic oil for his purposes, in his car... and that, in fact, good old fashioned dino oil is generally thought to be a better choice.

I don't want to get into a 'what kind of oil do you use?' thread here, I've read some of those and everyone seems to have their own opinions.

My question, essentially his question, is "What is this business I've heard about 'once you go synthtic, you must stick with synthetic'"?

Is it detrimental or would it be the end of the world if, at the next oil change he went to Rotella T and stuck with that, a heavy weight, high Zinc oil?

What's the issue with going back to dino oil?

[Jonny B]

Here is one reference - http://www.pennzoil.com/learn-about-motor-oil/synthetic-oil/

I did check a couple of other links, and the comment was the same, no problem with switching. The one caveat was to not mix synthetic and regular. Wait until the next oil change and then put in the regular oil.

[Panzer82]

Thanks Johnny B, your link cleared things up pretty quickly.

I think a lot of people overthink some of these things... not saying I don't want the right oil in my car... but there is lot of good marketing out that that make people think they need something they may not.

[Benz Dr.]

I've been running synthetic since 1982 which is likely far longer than most people I know. At that time, it was considered snake oil and now every oil company has some sort of blend or another. There's no question that it works but just like regular oil, some brands are much better than others.

Longer drain intervals are a reality with synthetic providing you have a good filtration system. In most cases, the oil filter supplied with your car will be OK but even oil filters vary greatly in quality. You can use synthetic in a 113 engine; I do it all the time. You can also use regular oil. Don't use synthetic during breaking in your engine or you won't get any break in at all; it reduces friction that much.

 One of the main differences I've noticed is that regular oil doesn't respond to long drain intervals very well and it will, at some point, drop its detergent package with a load of dirt all over inside your engine. Regular oil will also flash off the lighter fractions which is where all of that black or brown varnish comes from. Synthetic on the other hand, will hold on to its detergent package far longer because it is naturally more stable and requires fewer additives to keep it that way. Because it's man made they engineer the oil so that it's stable and not prone to viscosity break down. And, you can mix it with any oil you like.

I also use a lot of regular oil. I'm a big believer of having oil in your engine, preferably to the full mark.    

[stickandrudderman]

Apart from being a waste of money after running an engine on mineral oil for any length of time the detergents in synthetic oils can cause a real problem when switching from mineral because they liberate all of the black deposits from inside your engine which at best block the oil filter and at worst clog the oil pump.
I use synthetic in engines I've rebuilt AFTER THE FIRST OIL CHANGE.

[perry113]

I use oil that has ZDDP additives. This is the stuff the old engines need. I also agree that there is no harm in switching back from synthetic to conventional.

This is my hit list.

http://www.valvoline.com/our-products/motor-oil/vr1-racing-oil

http://www.penngrade1.com/products/High-Performance/SAE-20W50.aspx

http://www.cen-pe-co.com/Product%20Data/Super%20Racing%20Oil.pdf

[Benz Dr.]

Apart from being a waste of money after running an engine on mineral oil for any length of time the detergents in synthetic oils can cause a real problem when switching from mineral because they liberate all of the black deposits from inside your engine which at best block the oil filter and at worst clog the oil pump.
I use synthetic in engines I've rebuilt AFTER THE FIRST OIL CHANGE.

Not sure if I agree completely. It's not like a bar of soap where it cleans everything in sight. Detergents keep dirt in solution but don't always remove old crap from inside an engine. If it's really dirty and the stuff is loose, then it will remove what is loose but not much more. Ordinary engine oil will do pretty much the same if it's high detergent such as diesel oil. In which case, why put good oil in a POS? I've seen some very worn out 113 engines but it's very rare that I find one covered in black sludge.
 
Slightly off topic:
I've been running a 15W40 para synthetic in my 1982 combine since new. It has a Perkins non turbo diesel with about 4,000 hours on it. I change oil every 1,000 hours and the oil filter every 200 hours. The engine has never had a wrench on it, it's been over heated a hundred times, ( common thing for combines ) and it's sparkling clean inside. It has a few minor leaks that are really only places where oil gaskets seep out a bit.
  Since it uses about 1 liter of oil every 5 - 10 hours I'm always introducing fresh oil to the system. Oil samples indicate I can continue running from my last full oil change but I will be doing a full 23 liter change next summer before I start wheat. If it can do all of this for me at extended change cycles, under some very harsh running conditions, I'm pretty sure it would work well in one of our cars. 

[hauser]

Metric recommends using Castrol GTX 10W40.