synthetic vs organic oil

[pablo_o2]

As our engines are inbetween 30 or 40 years old and therefor not exactly designed for the use of synthetic oil, can it harm the engine? Is it better to use the "older" organic 10W40 e.g. instead of the more agressive synthetic kind? I somewhere heard,once you switch to synthetic oil, it is not good to change to organic again. Is this correct?

[rwmastel]

Paul,

Hi.  The synthetic oil issue has been discussed several times and I believe most people agree that it's better to use synthetic.  If you want to read all the details and arguments for/against, then use the Search link in the top right corner and search for "synthetic" and see what you get.

[hands_aus]

quote:Originally posted by rwmastel

most people agree that it's better to use synthetic.  

really?

[jameshoward]

I thought most people felt that synthetic was OK if you'd recently rebuilt your engine, otherwise use mineral. I've read a lot on the site about this, and it seemed to me that there are concerns about the detergents in synthetics that could lead to leaks in older non-rebuilt engines. I think people also feel that given the lack of zinc in modern oils, oils now developed for diesel cars are recommended. I use such a mineral oil and the car seems happy enough. The other thing people seem to agree on is that you should change your oil often, and ensure you have the dreaded and often missing rubber washer that sits a-top the oil filter when you change it. (I didn't have it, but I do now thanks to the chaps here).

But as Rodd points out, there's a ton of info and more opinions that you can shake a stick out here on the site on this topic. Happy hunting!

JH

[mdsalemi]

Pablo,

Without rehashing a lot here (search for "synthetics" or for "Mobil 1" one big issue with "modern oils" is the lack of ZDDP, a valve lubricant.

Many manufacturers, in their product line, have formulations specifically for older engines with extra valve lubricants.  I covered this in a Mobil 1 Redux thread a few months ago.

[pablo_o2]

thank you all guys

[Paddy_Crow]

Synthetic oils are superior lubricants. They maintain a consistent viscosity over a wide temperature range and will withstand more heat without breaking down.

One issue with older elastomers used in gaskets and seals is that the degree of swell is different with synthetic oils, which can cause a leak.

Newer oils will also have reduced additives. The reasons for this have to do with emission compliance in newer engines. This is independent of them being synthetic or organic.

[bsimaz]

The previous comments are correct.   If you have a newly rebuilt engine then synthetic is OK.  If you have an older engine, stick the traditional oil.  The synthetic will 'clean' the inside of you engine very good and cause leaks to start (with other problems).  I tried this and that's what happend to me.  started getting leaks and one of my valve guides came lose.  Causing much embarisment with a cloud of smoke following you down the road.  Once I noticed things were going bad I swiched back to the traditional oil and the problems have stopped.  

To quote my father-in-law (43 years as service manager at a car dealer that sold and serviced mercedes) " Get that moose piss out of you car".

[Benz Dr.]

Synthetic caused your valve guide to come loose? That's good one......

[Paddy_Crow]

quote:Originally posted by Benz Dr.

Synthetic caused your valve guide to come loose? That's good one......

Stem seal maybe?