Castrol / Mobil 1 blend?

Messages
17
Location
TX
I have 4 qts of Castrol GTX synthetic blend and 1 qt of Mobil 1 left over from previous oil changes. Both are 10W-30. Any problem mixing those together in an old Chevy 350 in which I've been running a variety of oils and weights from 5W-30 to 10W-40, both conventional and synthetic?
 
Messages
16,046
Location
Upper Midwest
Originally Posted by nomas
Some people here would die if they knew what I mixed over the years . No issues ever .
Of course not. As is always the case with this oft-repeated question, if the oils are API licensed then both must pass ASTM D6922 and will be miscible. The mixture will not cause immediate harm. But that isn't everything.
 
Messages
13,251
Location
1/2 hr N.E. of Detroit
Originally Posted by mbres2000
I have 4 qts of Castrol GTX synthetic blend and 1 qt of Mobil 1 left over from previous oil changes. Both are 10W-30. Any problem mixing those together in an old Chevy 350 in which I've been running a variety of oils and weights from 5W-30 to 10W-40, both conventional and synthetic?
You did good. This blend provides you with 20% less varnish accumulation, based on how GTX treated my engines during the late 80s thru mid 1990s..
 
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Messages
16,046
Location
Upper Midwest
Originally Posted by Triple_Se7en
You did good. This blend provides you with 20% less varnish accumulation, based on how GTX treated my engines during the late 80s thru mid 1990s..
What?
 
Messages
35
Location
Virginia
I used to have an old camry with over 240k miles on it. It would burn a quart of oil about every 500 miles or so like clockwork. Since it burned so much I would just buy the cheapest 10w30 I could find, it didn't matter what brand. I had another toyota that took 5w20 and required 4.5 quarts, so that leftover half a quart of 5w20 pennzoil platinum would go in the camry too. On top of that, I worked at a dealership detailing cars and would often find spare quarts of oil in the trunks of trade ins, those would go in the camry no matter what brand or weight of oil they were. If I was at a friend or family member's house and saw a dusty old quart of oil from the 80's in their garage I would ask them if I could have it and it would go in the camry no matter what it was. I was so broke I would even put in various oil additives I found in trade ins at the dealer (like restore or marvel mystery oil). Nothing ever changed how it ran, or how much oil it burned. I'm not saying it's ideal or it didn't hurt anything, but I did this for a couple years and it didn't seem to effect anything at all as far as I could tell. I certainly wouldn't advise putting the wrong weight of oil in a car, but I'm just telling you what my experience was.
 
Messages
4,559
Location
Decatur AL USA
Originally Posted by nomas
Some people here would die if they knew what I mixed over the years . No issues ever .
50/50 Mix of Motor Oil SA (No Brand Markings) & Store Brand HDEO for the win! What can I say? A 300,000 mi Slant 6 that leaks a quart every 600 mi could care less.
 
Messages
9,010
Location
Virginia
Originally Posted by kschachn
There are likely hundreds of threads on mixing oils here on Bitog. Perhaps read some of those?
Have you run out of your attitude improvement medication ??? LOL Certain topics have been introduced here a whole, whole, whole bunch of times on here.... From this place's very inception. This is just part of the dance so to speak.
 
Messages
9,010
Location
Virginia
Originally Posted by kschachn
Originally Posted by nomas
Some people here would die if they knew what I mixed over the years . No issues ever .
Of course not. As is always the case with this oft-repeated question, if the oils are API licensed then both must pass ASTM D6922 and will be miscible. The mixture will not cause immediate harm. But that isn't everything.
Very, very good point ^^^^^^ No guarantee of rated performance... Potentially cold performance could really be not the best either. Though in a majorly high percentage of times this has not been a issue for lots and lots of everyday people in their experiences.
 
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