Mineral Oil to Synthetic Oil and Back

**airshaq20** · May 27th, 2005 11:33 PM

To make it simple and short...there are advatages when shifting from mineral to synthetic but there is a bad part too (although its short term) - oil loss. But i dont see why you should go with synthetic and back to mineral - you can't mix synthetic and mineral safely. When you change your oil, there's still oil left in your engine.

So, when you decide to go with synthetic, stick with it. If you think you wont be able to afford to be consistent with the type of oil, then, you might be better sticking with your present oil - but, change it regularly.

**GlennSter** · May 27th, 2005 11:33 PM

ah..there is a risk...but not as risky as from mineral to full synth.

got it.

thanks mehn

**airshaq20** · May 27th, 2005 11:42 PM

...

A couple of words of warning:

If you've been driving around with mineral oil in your engine for years, don't switch to synthetic oil without preparation. Synthetic oils have been known to dislodge the baked-on deposits from mineral oils and leave them floating around your engine - not good. I learned this lesson the hard way! It's wise to use a flushing oil first.
If you do decide to change, only go up the scale. If you've been running around on synthetic, don't change down to a mineral-based oil - your engine might not be able to cope with the degradation in lubrication. Consequently, if you've been using mineral oil, try a semi or a full synthetic oil. By degradation, I'm speaking of the wear tolerances that an engine develops based on the oil that it's using. Thicker mineral oils mean thicker layers of oil coating the moving parts (by microns though). Switching to a thinner synthetic oil can cause piston rings to leak and in some very rare cases, piston slap or crank vibration.
Gaskets and seals! With the makeup of synthetic oils being different from mineral oils, mineral-oil-soaked gaskets and seals have been known to leak when exposed to synthetic oils. Perhaps not that common an occurrence, but worth bearing in mind nevertheless.

**jackaroo** · May 29th, 2005 07:29 PM

airshaq20,
I'm no "expert" in oils but i do my reading and use lab results. Have you heard of used oil analysis? I have my oils analyzed for viscosity, TBN, wear metals etc. which gives an unbiased snapshot of what's happening in the engine.
You can choose a viscosity based on lab tests after you benchmark the OEM oil.
Why go back to mineral from synth oil? Well, my synth oil soot levels were high at 6k km intervals so it was better to change more often with mineral.
I've used Mobil 1, Delvac 1, Conoco synth and others- most subjected to an oil analysis.