I have a quick oil question. Is it ok to mix 3 Quarts of Castrol 5w20 conventional with 1 Quart of Mobil 1 5w30? I figure since the Mobil 1 is synthetic it will almost match the viscocity of the 5w20 conventional.
MIxing 5w20 with 5w30
- Thread starter 90Notch
- Start date
- Status
Why Nawt?
I have a bunch of High Mileage Pennzoil 10W30 and 10W40 SL I'm going to mix with 5W20 SM yellow-bottle Pennzoil. Should put me right on spec, and give me the SL goodies the car was specc'd for in 2005.
I have a bunch of High Mileage Pennzoil 10W30 and 10W40 SL I'm going to mix with 5W20 SM yellow-bottle Pennzoil. Should put me right on spec, and give me the SL goodies the car was specc'd for in 2005.
That isn't a valid assumption. An oil's viscosity isn't determined by whether its base stock is conventional or synthetic.
I know all oils are supposed to be at least nominally compatible, but why do you want to mix these 2 in particular? If it's because you have them lying around and want to use them up, then as the others have said it shouldn't hurt anything, but be aware of the possibility of "additive clash"...in other words, the additive packs in the two oils may not be totally compatible and you may end up with an oil that doesn't perform as well as either the Castrol or the Mobil 1 would separately. It's a far better bet to mix 2 oils of the same brand and type; for instance Mobil 1 5W-20 and 5w30 are much more likely to be compatible, as would the two Pennzoil products mentioned by toocrazy2yoo above.
BTW, Castrol GTX has a viscosity of 9.1 cSt (@100°C) and Mobil 1 is rated at 11.3 cSt. Mixing them 75/25 will result in a new viscosity of 9.6. If this is what you're after, then rock on...
badnews, I'm not a tribologist, so I can't explain chemically how additive clash works, but basically it means that certain additives in oil "A" may not be fully compatible with the additives in oil "B", resulting in mixed oil "C" which may not perform as well as either "A" or "B" would alone.
I did a search on this board for "additive clash" and got 19 results...I didn't read every one, but maybe one of them can explain it better.
I did a search on this board for "additive clash" and got 19 results...I didn't read every one, but maybe one of them can explain it better.
Let's say addititve "clash" can be better expressed by saying additive "balance", whereas they need to be in proper proportions to compliment and not interfere with one another. I'm not exactly The Professor, but just repeating what reliable members have explained. I'll take the responsability for assuming what consitutes a "reliable" Member.
To further induce general panic, let's not forget that some additives work in different ways or simply work "best" with certian basestocks. I would not expect something like PP/Hi-Miles/Semi/Mobil 1 to be ideal mixed. So, where is the clash? I dunno, but is it reasonable to assume, even just common-sense assume, that umm, less-is more? That is, where do you draw the line? Two oils mixed, three? I'll mix for final visc, within the same brand, but that's about it. Same basestock is a plus, that's something I like about Havoline/Chevron products, you sorta know the base is the same, ditto with Mobil 1.
[ July 31, 2006, 05:45 PM: Message edited by: Auto-Union ]
To further induce general panic, let's not forget that some additives work in different ways or simply work "best" with certian basestocks. I would not expect something like PP/Hi-Miles/Semi/Mobil 1 to be ideal mixed. So, where is the clash? I dunno, but is it reasonable to assume, even just common-sense assume, that umm, less-is more? That is, where do you draw the line? Two oils mixed, three? I'll mix for final visc, within the same brand, but that's about it. Same basestock is a plus, that's something I like about Havoline/Chevron products, you sorta know the base is the same, ditto with Mobil 1.
[ July 31, 2006, 05:45 PM: Message edited by: Auto-Union ]
If there are 3 medicines to treat a condition, best take 1 of the 3, not a 1/3 of each.
- Status