tomc9

Hi Guys,

recently got my oil changed with standard conventional oil. I have a quart of penzoil ultra platinum sae 10w-30 full synthetic oil lying around and checked my oil level earlier seeing that it could use a top off. My question is whether or not it's OK for me to top off the conventional 5w-30 oil with this other brand. I plan to switch to full synthetic for my next oil change, but need to top off before this 6 hour drive tomorrow. Any help is appreciated, thanks!

frankjnjr

FWIW: It's NEVER, a good idea to mix oil, of a different viscosity! I'm not sure, about mixing full synthetic, with Dino oil, but I wouldn't think, that is a good idea, either.

horseshoez

iTrader: (2)

There really is no technical reason why oil of different weights and/or base oil compositions cannot be mixed; lots of folks build their own multi-grade oils by doing just this (not that I am advocating this approach as I don't see the benefit). The only proviso I can think of is I have heard of some chemical incompatibilities between conventional Group II oil being mixed with Ester based Group V oils.

losiglow

iTrader: (1)

I know next to nothing on the subject. But it seems logical that mixing different oil brands and types may not be good practice. If I were a quart low out in the middle of nowhere I'd add any oil I had in the trunk. But otherwise, I'd top it off with the same type of oil.

I think the exception might be different viscosities. If you had the same brand and type of oil, but it was a different viscosity (e.g., Mobil 1 EP w/ 0w20 in the engine and adding some Mobil 1 EP 5w30), it should be ok. That's simply based on what I've read on bobistheoilguy. Essentially that would only change the overall viscosity of the oil to whatever ratio you had of each oil. I've become a believer over the last few months that you should use the viscosity of oil indicated by the manufacturer but if you needed to top off on a pinch I don't think there would be any harm in doing something like that. But what you're describing; mixing one brand of conventional oil with a different brand of synthetic probably isn't best practice.

If I had some extra oil laying around, I'd consider purchasing the number of quarts of that oil to bring it to a full 5qts for your next oil change, and then purchase a quart or two of what you have in there now to top it off.