Blended oil.. what percentage ?

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Oct 10, 2021
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I only use full synthetic mobil 1 in four diff weights for different vehicles and summer / winter use.. i find oil is cheap and engines are expensive. I do my own service as I dont want stripped drain plugs...
In the past many decades ago I bought conventional oil. And must have 20 to 40 quarts left.. i keep about 50 quarts or more of mobil 1 .
I have at times used 60 percent or 70 percent full synthetic and added dino oil for the rest.. that seems ok to use up the dino oil so its not wasted.
When you buy blended oil.. does anyone know what percentage is dino oil and what percentage starts as full synthetic??
I am curious even if I dont use it to know if its a good value ?
And would you be better off making your own mix??
I am sure on a commercial line its not two vats of oil with valves to adjust the proportions. I assume that additives are special to blended oils.
 
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Just a guess, but I'd probably do 50/50 or 75/25 conventional/synthetic to use up the free conventional, and run about 3k-5k or 6 month oil changes. Or just use up the conventional on short OCIs of 3K and then switch to blends or full synthetics since they are so cheap now.

There's an oil mix calculation website that gives you the weight of oil if you mix different weights but after fussing with it I found it's just simple math. A 50/50 mix of 20 and 30 weights gives you a heavy 20 or a light 30 weight, since there's not a "25" weight.

Oil should last for decades if stored correctly. But for really old oil, I would pour each bottle into a clear bottle to inspect for any separation, contamination, water or moisture, etc. and discard any that are bad.
 
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I have used up all of my conventional oils the same way you are doing by mixing it with the synthetic oils in my stash. Now, I just stay with synthetic oils. You can mix them in any % you want to, just to rid yourself of the old conventional.

Synthetic Blend Oils that are labeled as such, could be any % of synthetic but I am sure it's mostly conventional. My understanding is that...most advertised "synthetic blend" is somewhere ~ 15%-25% syn oil mixed in with the conv. But I don't think anyone really knows and the blenders and/or oil companies don't have to say.

Years ago, I just assumed that a blend was 50/50 but I learned here at BITOG that I was wrong. That's not to say that there aren't true 50/50 blends but who know which brands are that particular mix? ... I certainly don't know!

With todays conventional motor oils, most brands are of a synthetic blend oil (ANYWAY) even though they're not labeled as such. The oil company's website says so right in their PDS that these conventional oils are mixed with some syn oil. How much syn oil? Again, who knows? 5%-7%? Maybe 10%??? IDK!

IMO ,the specifically labeled "SYN BLEND" oils ARE NOT a good value as we just don't know what mix of each we're getting and probably not worth the extra cost. I'd prefer to mix my own in this case...if I were to have both conventional & synthetic oils lying around.

Also, todays specifically labeled "FULL SYNTHETIC" motor oils are mostly Group III(HydroProcessed or GTL-Gas to Liquid) motor oil, not a Group IV(PAO). Then of course, there is Group V(ESTER).
There is much to learn on these different groups of SYN oils. In a nutshell:

Group III - HydroProcessed/HyrodCracked Synthetic Oil: Is the pumped out of the ground crude oil that is processed to or at a point that alters the chain molecules to rival the scientifically designed motor oils such a Group IV(PAO). I can't really answer for the process of GTL Syn oil or ESTER without looking it up myself.

Just for myself/in my head, I call Group III synthetic oil- crude oil. But a really good crude oil. The best crude oil.
And I call a Group IV(PAO) synthetic oil- a laboratory created synthetic oil

^^^And IDK if I said any of that correctly so please forgive/correct me if needed. :)
 
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Quantico

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Thanks. I just did a change. But might start using up oil in the spring with short mikeage runs.
I appreciate your info a lot.. sounds like what I guessed...but have no hard data on...thanks
 

SR5

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When I spoke to Valvoline and Penrite over the phone a few years ago, they said their semi-synthetics were about 30% synthetic (Valvoline ) and over 20% synthetic (Penrite). This was back in the API SN days, not sure about modern SP oils. I'm also sure it is a Group II and Group III blend, as Penrite was clear on this when I asked them. No dodgy Group I and no fancy pants Group IV or Group V.

However in Europe I believe, unlike Australia or North America, they previously used Group I in their semi-synthetics which required a higher percentage of Group III to compensate.

I also recall a few threads about Pennzoil Gold semi-synthetic which was Dexos1-Gen2 rated, and it was 50% synthetic, clearly printed as such on the jug.
 
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I also would blend the conventional with synthetic at 50/50 to use it up. Living in WI, you might run more synthetic in winter to take advantage of the cold flow properties, and run more conventional in summer. Just a thought.
I just bought 2 jugs of Napa syn blend for my neighbor's van, it was on sale for the exact same price as their conventional product.
 
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Price is not always a good indication but based on retail pricing where blends are about 3/4 the price of a full synthetic by the same company, I would un-expertly suspect that the ratio must be somewhat close to that or around 50/50. Just another data point for consideration.
 

Quantico

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I also would blend the conventional with synthetic at 50/50 to use it up. Living in WI, you might run more synthetic in winter to take advantage of the cold flow properties, and run more conventional in summer. Just a thought.
I just bought 2 jugs of Napa syn blend for my neighbor's van, it was on sale for the exact same price as their conventional product.
Here in wis the super cold temps definately encourage the more synthetic the better.
I just prefer to get rid of my collection of conventional oil even if its slowly.
 
Joined
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Northern Wisconsin perhaps. Here in southeastern Wisconsin it rarely gets below -20F so any oil with a 5W winter rating is quite sufficient.

Base stocks don’t tell the story that the winter rating does. Synthetic oil results in the same relative winter rating that a conventional oil will. The testing is agnostic to the base stock composition.
 
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VA
I only use full synthetic mobil 1 in four diff weights for different vehicles and summer / winter use.. i find oil is cheap and engines are expensive. I do my own service as I dont want stripped drain plugs...
In the past many decades ago I bought conventional oil. And must have 20 to 40 quarts left.. i keep about 50 quarts or more of mobil 1 .
I have at times used 60 percent or 70 percent full synthetic and added dino oil for the rest.. that seems ok to use up the dino oil so its not wasted.
When you buy blended oil.. does anyone know what percentage is dino oil and what percentage starts as full synthetic??
I am curious even if I dont use it to know if its a good value ?
And would you be better off making your own mix??
I am sure on a commercial line its not two vats of oil with valves to adjust the proportions. I assume that additives are special to blended oils.
I don't think you will find any set value of the percentage of synthetic in the oil, I think technically per regulations it could theoretically have like 1% synthetic and they could still in fact call it a synthetic blend.

I too know about stripped drain plugs, my dad used to take his 2006 F150 w/ 4.6 to another dealer every so often for service but last time I changed the oil in it I had the replace the plug and I've never seen anything like it before and dad said it looked like they split the thread, it looked like there were 2 threads and with the new one it doesn't appear to be leaking so might've gotten lucky.

I need to change oil too myself, all of my vehicles haven't been changed in 2-3 yrs but I run full synthetics and now is a good time to do so before winter comes along.
 
Joined
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If memory serves, 10% synthetic added to conventional oil 'qualifies' as a blend.
Of course, the better brands go well above that. 40% IIRC.


My 2¢
 
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