is it acceptable to mix 5 with 10 weight, or mix valvoline with mobil for example

 

Depends on what you call "acceptable".

I've been using synthetic and petroleum based oils for more than a decade now, and I've learned really more than I want to know, and I'll try to fill you in on the salient points.

But..I had the same question. I once submitted a USED mixture of 5W-30 synthetic Mobil-1 equal mixture with 10W-30 petroleum Valvoline. ALL parameters came into spec for the oil. The viscosity reported was 7.5W-29 (the slightly lower top number resulting from slight dilution over time due to crankcase blowby).

In reality - ALL weights and brands of motor oil are mixable. Now, they may not perform as well (or they might even perform better) as the manufacturer intended them to work mixed with EITHER another grade or brand of oil, but they still perform in a manner that will be almost an even mixture between the two oils. Consider, though, that if you ran low on oil and stopped at an Interstate stop in convenience store, and bought one quart of another manufacturer's oil and added it to the crankcase and 10 miles later blew the engine as a result of "incompatible" oil. Think that would blow over easy? Nope. Lawsuit. The oil manufacturers do seem to have some unwritten law that they won't add any component to the oils that will make them totally incompatible with another manufacturer.

On further, SOME people believe that a mixture of different manufacturer's oils may perform BETTER than a pure crankcase. For example, some manufacturers have more detergent component than others (Mobil-1, Amsoil), while others have more high pressure additives (Pennzoil). Engineers at each plant believe that the applications of their oil deserve more or less of different components, and perhaps the best compromise is an intermediate blend of those oils. Consider, if you will, the "synthetic blends" - they have clearly better qualities than that of petroleum based oils, but are not as expensive of the full synthetics. Now, the real argument here is do we really need these better lubricants, or are we paying too much for an added benefit we don't really use - I cannot settle that argument, and it goes on for YEARS in the "synthetic" vs. "dino oil" camps.

Anyway, in summary - no one RECOMMENDS mixtures of different weights or different manufacturers, but they never seem to be problematic for those who use them regularly, or are forced to use them as a victim of circumstance.

Shawn

 

shawnhayes=

 

Damn Shawnhayes really knows his oil.

 

How about mixing a dino oil with a synthetic one - of the same grade. I assume that is ok too? I had to top off since my dino oil change severeal times with synthetic bc I had nothing else.

sorry to bring this back from the dead, but there is good info here that I'm sure someone will find useful.

 

This brings up an interesting question. If mixing oils may indeed create an all around better oil, what is the happy medium? How would we find out the exact mix of additives and detergents that our particular car "likes"?