Zurichgnome

Guys, I'm pulling my car out of storage this weekend and will do an oil change.

I have 5 quarts of Mobil 1 0W/40 and a few quarts of Mobil 1 10W/40 for my wife's car sitting in garage. Am I asking for trouble by mixing these?

No problem to buy a few more quarts of 0W/40, but just wondering if there is an issue with this -- if it's just that I net out at something like 3.5W/40, Not sweat.

Any chemistry issues here I am overlooking?

Thanks,

Quadcammer

meh, I might take a look at the chemical make ups on the mobil site to see if these two weights are comparable. If so, mix with reckless abandon

logray

It would work fine.

http://www.mobiloil.com/usa-english/...aqs.aspx#FAQs5

Can different synthetic motor oils be mixed together?
Mobil 1 is fully compatible with conventional motor oils, semi-synthetic motor oils and other synthetic motor oils, should it be necessary to mix them. However, it is important to note that the superior performance of Mobil 1 will be reduced by diluting it in any way.

nitrorocket

Nope, your figuring exactly right, mix away, wont hurt a thing...

KNS

Perfectly fine - although one should stick with the same brand, as you are doing.

Macster

If your wife's car is a Porsche Porsche doesn't recognize 10w-40 as suitable for use in your wife's car. No 10w-40 oil is on Porsche's approved oil list.

Porsche states that approved oils are miscible, that is when changing from one approved oil to another there's no reason to flush the oil, but when topping up that if possible the same oil be used.

It is up to you but my advise would be to just buy the necessary few quarts of the right oil.

You might be able to swap the unopened bottles of 10w-40 oil for the oil you should use.

Sincerely,

Macster.

logray

There is an indy Porsche shop owner who frequents renntech.org and others and is quite knowledgeable with the 986/7 and 996/997.

He swears by a certain 10w40 product, castrol I believe and uses it on a lot if not all his customers cars.

He says it holds up better under UOA than oils with a wider spread, due to less fillers perhaps.

IIRC a 10w40 oil was a recommended oil at some point (perhaps early on in the 996 life), in fact I think that's what my owners manual recommends. I wonder how many people would never look at what the latest recommended oils are but rather just go off of what their owners manual says. It's not like Porsche sends owners updates to the manual in the mail.

Kazual99

My manual has 10W40 as an option as well, along with others. Curios though is the exclusion of 0w40 as a option per my manual.

Pac996

Old days a law was made so that mixing oils wouldn't cause problems. For the different weights of oil blends I think you are just doing the same thing they do when making 10w50 or so. In other words enjoy the 5w40 if thats what the blend figures to be

nick49

On my previous 996 I made a blend using mainly 10W40 or 5W40 synthetic and throwing in quart of motorcycle 20W50 with a paraffin base. This gave a bit of ZDDP to the mix and also is friendly to the lifters and seals.

With today's oils you can mix any brand with any other brand and any weight.

Hurdigurdiman

Just buy yourself the correct amount needed to make your oil change for yours. Buy the other needed to make the oil change for your wifes car. Its not as though you wont be changing oil again. Nothing wasted that way.

DaveSpeed

It may be safe but I would not mix oils.