"Partial" oil change.

Joined
Feb 25, 2009
Messages
199
Location
TX
I have about 2 qt of Super-Tech Dino oil that I'm not inclined to waste. My car calls for 4.3 qt each oil change. Would it be safe to drain out 2 qt of old oil, then replace with new and extended the complete drain and fill interval another ~1,000 miles? I'm just extrapolating logic from a transmission drain and fill, where half the old fluid still remains in the torque converter. I think the oil filter can make it until the complete drain.

Thanks.
 

4WD

$50 site donor 2023
Joined
Sep 21, 2010
Messages
20,092
Location
Texas
I have about 2 qt of Super-Tech Dino oil that I'm not inclined to waste. My car calls for 4.3 qt each oil change. Would it be safe to drain out 2 qt of old oil, then replace with new and extended the complete drain and fill interval another ~1,000 miles? I'm just extrapolating logic from a transmission drain and fill, where half the old fluid still remains in the torque converter. I think the oil filter can make it until the complete drain.

Thanks.
Would you use those 2 quarts on the next change … ? If not - they might extend your current oil by 2k ?
What‘s miles on current oil filter ?
 
Joined
Jul 9, 2008
Messages
3,461
Location
British Columbia, Canada
I have about 2 qt of Super-Tech Dino oil that I'm not inclined to waste. My car calls for 4.3 qt each oil change. Would it be safe to drain out 2 qt of old oil, then replace with new and extended the complete drain and fill interval another ~1,000 miles?
This is not such a great idea. You're doing the same amount of work (or even more work depending on how you plan to drain only 2 quarts) and then using up 2 quarts of perfectly good oil for little benefit.

It would be better to get 2 more quarts of the same oil and just change it.

Or use these 2 "extra" quarts for top ups, or changing the oil in the mower, or something like that.
 

Jarpin

Thread starter
Joined
Feb 25, 2009
Messages
199
Location
TX
Thanks guys, the thing is... it's dino and the car currently has dino old oil in it, which isn't available anymore from WM. I just thought if I'm doing a complete change, then I'd be better to use either 100% dino, or 100% Syn blend.
 
Joined
Jul 9, 2008
Messages
3,461
Location
British Columbia, Canada
Thanks guys, the thing is... it's dino and the car currently has dino old oil in it, which isn't available anymore from WM. I just thought if I'm doing a complete change, then I'd be better to use either 100% dino, or 100% Syn blend.
A mix of synthetic and dino would be just fine. I'd use all the same brand though.

Or you could use the dino oil for a top up after a 100% synthetic oil change (which will only be 80 or 90% synthetic oil after the first change anyway).
 

Jarpin

Thread starter
Joined
Feb 25, 2009
Messages
199
Location
TX
A mix of synthetic and dino would be just fine. I'd use all the same brand though.

Or you could use the dino oil for a top up after a 100% synthetic oil change (which will only be 80 or 90% synthetic oil after the first change anyway).
I'm not going to use 100% synthetic yet on this car, because it's 20+ years old, and I don't want the advanced detergents in the synthetic to scoop up dirt in the sealing surfaces/gaskets that could be preventing leaks, thus creating new leaks. I'll transition to synthetic blend only for now.
 
Joined
Jul 9, 2008
Messages
3,461
Location
British Columbia, Canada
I'm not going to use 100% synthetic yet on this car, because it's 20+ years old, and I don't want the advanced detergents in the synthetic to scoop up dirt in the sealing surfaces/gaskets that could be preventing leaks, thus creating new leaks. I'll transition to synthetic blend only for now.
A synthetic blend is synthetic plus dino. Which is what you'd get if you mixed your dino oil with synthetic oil.

And a modern dino oil (ie API SN) is probably the equivalent of a mix of synthetic and dino anyway. Theory is it's likely not possible to meet modern requirements for a SN oil without some "synthetic" component.

So you could use your 2 quarts of dino with 2 quarts of semi-synthetic and you'll be right where you want to be.
 
Joined
Apr 4, 2012
Messages
15,914
Location
Kendall, FL
Thanks guys, the thing is... it's dino and the car currently has dino old oil in it, which isn't available anymore from WM. I just thought if I'm doing a complete change, then I'd be better to use either 100% dino, or 100% Syn blend.
Buy online.
 
Joined
May 24, 2009
Messages
1,042
Location
So Cal
In reality you never drain out all the oil on an oil change, no matter how long you let it drip. My Miata takes 4.5 quarts but has a capacity of 5.3 quarts when engine is dry of oil. Sounds like you have a easy way to remove 2 quarts or you would not attempt it. I would say a month before your scheduled OCI do the 2 quart change and run it. That would help clean out all the older oil in the regular OCI. Just another view…
 
Joined
Oct 27, 2018
Messages
661
Location
MD
I'm personally not sure what are you trying to achieve here in your suggested senario. If time is an issue you can take a walk a little bit
 
Joined
Dec 28, 2011
Messages
4,299
I have about 2 qt of Super-Tech Dino oil that I'm not inclined to waste. My car calls for 4.3 qt each oil change. Would it be safe to drain out 2 qt of old oil, then replace with new and extended the complete drain and fill interval another ~1,000 miles? I'm just extrapolating logic from a transmission drain and fill, where half the old fluid still remains in the torque converter. I think the oil filter can make it until the complete drain.

Thanks.

That logic is flawed when it comes to engine oil change. At least that is my opinion. As others have said, but a few more quarts for a full oil change or use it to top off. Heck, even buying a few quarts of even cheaper oil in your grade and spec for a full change is better than a 2 quart drain/fill.
 

Jarpin

Thread starter
Joined
Feb 25, 2009
Messages
199
Location
TX
A synthetic blend is synthetic plus dino. Which is what you'd get if you mixed your dino oil with synthetic oil.

And a modern dino oil (ie API SN) is probably the equivalent of a mix of synthetic and dino anyway. Theory is it's likely not possible to meet modern requirements for a SN oil without some "synthetic" component.

So you could use your 2 quarts of dino with 2 quarts of semi-synthetic and you'll be right where you want to be.
Ok...how about mixing the Dino with 100% FULL synthetic to achieve a "blend" composition? Is that safe to do?
 
Top