Mixing synthetic oil?

radman1 · Feb 8, 2009

I have Mobil 1 and Valvoline Premium Blue diesel synthetic oils. Bought the Valvoline when couldn't find Mobil 1. I have about 2 qts of Valvoline left over both are 5W-40 and same rating. Can I mix the two together to get rid of the Valvoline?

MikePA · Feb 8, 2009

Yes, you can mix them.

groundcover · Feb 8, 2009

I would get enough Mobil-1 to keep it all the same and use the other for your other small engines, from what I understand some of the additive packages are different and don't like to be mixed.If you don't have time to go shopping,you should be ok,the engine is like the brain,it just needs to be wet!

AKfish · Feb 8, 2009

If the Valvoline is a true synthetic; I would not see a significant problem. (But I'm not an oil "purist", either.)

IMO - the major difference between the 2 oils is likely the additive package; i.e. higher phosphorus, cadmium and other anti-wear components.

However, my Ford PS takes 15qts and the DuraMax, 10qts. So, 13% - 20% less additives (or more) than what is in the Mobil 1 would not be critical.

AKfish

nmu98 · Feb 8, 2009

I would say go for it like the rest of the guys stated. The only way I would not is if the ratings were not the same. IE Api ratings, or one was CH and other CI......

radman1 · Feb 8, 2009

groundcover said:
I would get enough Mobil-1 to keep it all the same and use the other for your other small engines, from what I understand some of the additive packages are different and don't like to be mixed.If you don't have time to go shopping,you should be ok,the engine is like the brain,it just needs to be wet!

Forgot to say in the original post, both are pure synthetics and for diesel motors. Don't have any small engine diesels that would only use 1-2 qts.

Gary Fowler · Feb 9, 2009

I always avoid mixing brands of oils, but I dont know of any studies that says that your engine will blow up if you mix Mobil with Shell or whatever. As long as they are the same API grade, they should be similar enough that they will mix and perform as required.
I just read a post yesterday where a member said that he gets rid of his spare oil by mixing it with his diesel. NOT used oil, new oil that you end up with a quart or half quart etc and nothing to do with it. The diesel engine will burn it easily with no harm done.

nmu98 · Feb 9, 2009

Gary Fowler said:
I always avoid mixing brands of oils, but I dont know of any studies that says that your engine will blow up if you mix Mobil with Shell or whatever. As long as they are the same API grade, they should be similar enough that they will mix and perform as required.
I just read a post yesterday where a member said that he gets rid of his spare oil by mixing it with his diesel. NOT used oil, new oil that you end up with a quart or half quart etc and nothing to do with it. The diesel engine will burn it easily with no harm done.

I don't think I would want engine oil with its additives going through my diesel. Maybe my 1970 or 80's diesel that does not run 30,000psi in the injectors.... But I would not even risk it in my tractor......

CurlyDave · Feb 9, 2009

NOT used oil, new oil that you end up with a quart or half quart etc and nothing to do with it.

That just never happens to me. Just keep it in the garage and when the oil level drops between changes, top it off.

AKfish · Feb 10, 2009

CurlyDave said:
NOT used oil, new oil that you end up with a quart or half quart etc and nothing to do with it.

That just never happens to me. Just keep it in the garage and when the oil level drops between changes, top it off.

Yep... works that way around here, too. And for some of the older, non-synthetic oils (new, not used) that I've got around - I blend it in my chain saw oil to thin it a bit for cold weather use.

AKfish