Achilles99
Enthusiast
I found 6 quarts of Amsoil 10w30 in my garage. Is it safe to mix it with 4 quarts of Mobil 1 0w30 (which I also have lying around)?
Is it safe to mix different brands of synthetic oil?
- Thread starter Achilles99
- Start date
I don't think it will hurt, but I wouldn't do it due to different detergents that may cancel one out from another.
GTSJERRY
Enthusiast
You shouldn't have a problem, i once spoke with a rep. with an oil company that told me the gov't standards and requirements make it hard for the oil comp. to determine with oils are theirs so they put a tracer dye in them to tell the difference.
AJT
Enthusiast
I have always "heard" not to mix different oils. Something about the way they are made & exact ingredients are not the same? I wouldn't do it.
my .02
Andy
my .02
Andy
99 R/T 10
Enthusiast
Where is Tom the "oil&Gas" guy? He'll know 
NDW
Enthusiast
A local AmsOil rep. has a garage at the track where he has a clientel of 20+ race cars he works on full time. He also used to work in a well known Viper tuners shop. I was out of Mobil1 at the track one day, and he said it was fine to mix the AmsOil with Mobil1. He gave me quite an education on synthetic oil that day, although I don't remember all of the specifics. I mixed one quart in with 9 of Mobil1 and suffered no ill effects.
Achilles99
Enthusiast
Where is Tom the "oil&Gas" guy? He'll know
I thought about that as soon as I made this post... here is Tom's response (note-my plan was to use 6 quarts of Amsoil, and then fill up the rest of the way with Mobil 1 0w30):
Normally I'd say adding a different quart (topping off) to an engine is far more preferably than not adding it, but in this example I would not recommend mixing.
1)You have a large percentage of the other oil.
2)Additives in the oil typically underperform until there is enough of the same additive.
3)You would have two sets of potentially underperforming systems.
4)More unlikely, but possible, is an antagonistic effect, although when I've seen it, it's mostly cosmetic (oil becomes hazy, but works fine.)
I'd worry most about #3. But since additives get used up, you're OK until one of those protection systems quit, so if you really want to use the oil because you have nothing else to do with it, shorten the drain interval to 60% of what you normally do (i.e. pretend you have 100% of the fluid but only 60% of the additive package.) And lastly, the viscosity will be a sort of mathematical average, so like a 6W-30 (if there was such a thing.)
GoldenVenom
Viper Owner
Simplest solution: buy 4 more quarts of Amsoil 10w30 and 6 more quarts of Mobil 10w30, then you will have enough for 2 complete oil change. I think it is ok to mix. I am not an oil expert but I do not want to take a chance. I would put in a quart of regular oil only if it is an emergency.
Achilles99
Enthusiast
I recently moved to NC, so I don't have my normal Amsoil dealer to rely on. Not so simple for me
Fast Freddy
Enthusiast
it is not good to mix oil of different weights as told to me by a petrol chemist from a major oil and gas manufacturer that i once had a sponsorship from. mixing oil of the same weights but from different manufacturers is the lesser of two evils.
Achilles99
Enthusiast
Here's another response from Tom... this time, I asked what the viscosity numbers meant. I think I'll just use 0w30 from now on
FROM TOM:
The "0W" part is measured at low temperatures, far below freezing, in fact at -35C for one test and -40C for another. However, in formulating race oils, it can also be looked at as how hard it is for the oil pump to force the fluid through the oil passages and into bearings. Think of sucking a straw stuck in a milkshake vs. milk. Then blow the fluid out the straw. Lot harder with milkshake than milk. Diesel engine oil pumps deliver 10's of gallons per minute and consume 15-20 hp, I think I remember, while gasoline engines are less. But saving 2 or 3 or 4 hp at no cost is always good.
The second number is when the oil is hot, but can loosely be related to how the oil behaves in the bearing. The spinning part, the crank journal or rod journal, is actually surfing over a film of oil and while the 60 psi may seem like what "supports" the moving part, it is not. It only determines whether the oil gets to it's destination or not. The pressure under the theoretical surfboard is 1000's of psi and the oil has to maintain it's film strength to prevent metal contact. So now it has to behave like a thick oil.
Ideally, the W number is as low as you can get it, while the second number is just big enough to keep all the metal parts separated. So 0W-30, 5W-40 are actually very good choices, but because they are made with synthetic base oils (because they can be, and can't so easily be made with mineral oils) they are not very common. Unfortunately, the unfamiliarity of the odd viscosity combination then becomes a barrier to market entry - as you are experiencing - even though it's a really good system.
FROM TOM:
The "0W" part is measured at low temperatures, far below freezing, in fact at -35C for one test and -40C for another. However, in formulating race oils, it can also be looked at as how hard it is for the oil pump to force the fluid through the oil passages and into bearings. Think of sucking a straw stuck in a milkshake vs. milk. Then blow the fluid out the straw. Lot harder with milkshake than milk. Diesel engine oil pumps deliver 10's of gallons per minute and consume 15-20 hp, I think I remember, while gasoline engines are less. But saving 2 or 3 or 4 hp at no cost is always good.
The second number is when the oil is hot, but can loosely be related to how the oil behaves in the bearing. The spinning part, the crank journal or rod journal, is actually surfing over a film of oil and while the 60 psi may seem like what "supports" the moving part, it is not. It only determines whether the oil gets to it's destination or not. The pressure under the theoretical surfboard is 1000's of psi and the oil has to maintain it's film strength to prevent metal contact. So now it has to behave like a thick oil.
Ideally, the W number is as low as you can get it, while the second number is just big enough to keep all the metal parts separated. So 0W-30, 5W-40 are actually very good choices, but because they are made with synthetic base oils (because they can be, and can't so easily be made with mineral oils) they are not very common. Unfortunately, the unfamiliarity of the odd viscosity combination then becomes a barrier to market entry - as you are experiencing - even though it's a really good system.
onerareviper
Enthusiast
Go to Walmart and spend $19.88 of a 5 quart jug + $4 1 quart (Mobile 1) for 'piece of mind'. For $25 bucks it's not worth worrying about... Then just use the Amsoil in your other car which probably has a smaller quart capacity.
GraphiteGTS
Enthusiast
How can it hurt? I'd say you could never tell the difference.
Once the dealer "accidently" mixed syn w/non-syn oil in a Vette and I could never tell the difference.
I believe that there are a lot of old wives tales when it comes to mixing oil.
Once the dealer "accidently" mixed syn w/non-syn oil in a Vette and I could never tell the difference.
I believe that there are a lot of old wives tales when it comes to mixing oil.
