Were they at least brewed from the same genus of dinosaur? Thats the go/no-go line
question about mixing engine lubes
- Thread starter TBoss1
- Start date
That's my 
favourite brew, for my Subaru; grades too!
favourite brew, for my Subaru; grades too!
Last edited:
CleanSump
Site Donor 2026
I'm afraid you may have mixed North Sea oil with Pennsylvania Crude and a huge rift is now opening in the Atlantic seabed.
4wd
$50 site donor 2026
Have never had any of my franken brews curdle.
No
CleanSump
Site Donor 2026
The majors (including Castrol and Quaker State) all state mixing OTS brand oils of the same ratings/approvals is ok. Check the VOAs and you'll find the same ingredients to vary degrees. A little difference in PPM of moly or magnesium won't make them incompatible.
You can almost argue that “mixing engine lube” happens every time you change the oil if not the same oil as previous OCI. There’s too many variables that leave significant residue in the nooks and crannies and pan which just mixes with the new stuff going in. Did I change it hot or cold? Was vehicle on ramps? Was it an older Honda model that recommended oil filter replacement every other change. Do you have a summer grade vs. winter grade? Did I let it drain for hours or 5 minutes? So for discussions sake, there could be 1/2qt + still in there. Even my Toyota emphasizes using the proper grade and if any alternative listed is ok but recommends going back to what’s called for so I don’t think Toyota can lock you in brand or mixing grades. Would I purposely mix something like 50/50? Probably not but don’t think an engine would adversely be effected short term and many have done so too.
I love me a good Frankenbrew.... Back in the day when money was scarce, at least we knew, "Any oil is better than no oil."
“What oil you runnin’?”
“Oh, a mix of this and that, it’s wet and slippery.”
If it works, it works!
You didn't do it right unless you put in a little Marvel mystery oil 
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