Mixed engine oil Q

[SurboNight]

Hi,I have an extra engine oil left for about half a litre,and the next service got half a little more.My question is if I mixed up my leftover engine oil into one container (eg:synthetic+mineral based oil summore different brands) and then used it for the next service when the container is full can give harm to my engine?Thanks.

 

[g88]

http://www.carbibles.com/engineoil_bible.html

 

[SurboNight]

Mixing Mineral and Synthetic oils - the new hotness

That's the thing with progress - stuff becomes out-of-date. Fortunately for you, dear reader, the web is a great place to keep things up-to-date, so here's the current thinking on the subject of mixing mineral and synthetic oils. This information is based on the answer to a technical question posed on the Shell Oil website.
There is no scientific data to support the idea that mixing mineral and synthetic oils will damage your engine. When switching from a mineral oil to a synthetic, or vice versa, you will potentially leave a small amount of residual oil in the engine. That's perfectly okay because synthetic oil and mineral-based motor oil are, for the most part, compatible with each other. (The exception is pure synetics. Polyglycols don't mix with normal mineral oils.)
There is also no problem with switching back and forth between synthetic and mineral based oils. In fact, people who are "in the know" and who operate engines in areas where temperature fluctuations can be especially extreme, switch from mineral oil to synthetic oil for the colder months. They then switch back to mineral oil during the warmer months.
There was a time, years ago, when switching between synthetic oils and mineral oils was not recommended if you had used one product or the other for a long period of time. People experienced problems with seals leaking and high oil consumption but changes in additive chemistry and seal material have taken care of those issues. And that's an important caveat. New seal technology is great, but if you're still driving around in a car from the 80's with its original seals, then this argument becomes a bit of a moot point - your seals are still going to be subject to the old leakage problems no matter what newfangled additives the oil companies are putting in their products.

So,in other words,I still can mixed up my unused syn+mineral oil in one container laa.Thanks bro for the info:regular_smile: