Mixing engine oils? - Mobil 1 and Castrol Syntec

[Moose201]

I'll be performing my first oil change and plan to use Mobil 1 0w40. I also have two or three quarts of Castrol Syntec 5w40 leftover from my last car. Don't want to see it go to waste but not really sure if it's wise to mix it in with the Mobil 1. What say you?

[audi49]

I say OK.

[shadycrew31]

You can mix other grades but not other oil brands/blends. At least thats what Mobil 1 says, a crate engine costs $16,xxx+ there's no point is risking it for $15 worth of oil.

[Trev996TT]

I've mixed oil before without issue, but not on this car. What I would do is stick with one brand for the oil change and use your leftover Castrol for top ups between oil changes.

[Skywagon]

FWIW, I've done it, no problems.

[saxon]

Oil is oil is not like it will mix and turn into water

You're fine

[Tifosi]

Its okay to mix different brand or weight oil, there is little chance of the additives reacting against each other. However, why not just save the Castrol oil for topping off in between the oil changes instead of as part of the routine oil change ?

[infinkc]

Its okay to mix different brand or weight oil, there is little chance of the additives reacting against each other. However, why not just save the Castrol oil for topping off in between the oil changes instead of as part of the routine oil change ?

I was just going to say the same thing.

[S4 00 2.7]

I've mixed oil before without issue, but not on this car. What I would do is stick with one brand for the oil change and use your leftover Castrol for top ups between oil changes.

+1 what I do as well

[mattchat]

According to engine oil regulations they are manufactured so they meet a certain criteria so that you can mix brands (even synthetic with regular oil). I prefer to use the same...cause I don't like mixing drinks, but it is perfectly safe.

[StL_Stranger]

Guys im a little late to this, but i need some advice.
I changed my oil and used full sythentic and it leaked on me at the o rings so i fixed the issue and i needed to add 1 bottle to tap it off. Well i accidently added half of bottle of sythentic BLEND until i realised i got the wrong bottle in hand. Will this cause me any issues ? Or shoulf i be ok ? Or should i change oil all over again ?

[B8A42010]

You can mix other grades but not other oil brands/blends. At least thats what Mobil 1 says, a crate engine costs $16,xxx+ there's no point is risking it for $15 worth of oil.

Your right, i paid 17300 for a brand new crate motor through audi.

[Dr GP]

Guys im a little late to this, but i need some advice.
I changed my oil and used full sythentic and it leaked on me at the o rings so i fixed the issue and i needed to add 1 bottle to tap it off. Well i accidently added half of bottle of sythentic BLEND until i realised i got the wrong bottle in hand. Will this cause me any issues ? Or shoulf i be ok ? Or should i change oil all over again ?

You are fine. Guys that have done oil analsis on their cars have shown that High quality full syntheic oil is still protecting at 7500 miles. If you put in some synthetic blend , you might want to do your next oil change at 5k. Many do it at 5k with full synthetic, but thats their choice.

[amz]

Why not put them up on Kijiji or something, sell them at 60% price and do a complete oil change with a single brand?