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Mixing oil types

Mastiff

Mastiff

1/2 ton status
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This is actually not about my K5, but I think the people here may be less likely to get all uppity than the people on the Tacoma forum... I need to change the oil on my truck, and the recommendation is 0w-20. That always struck me as crazy since I live in Arizona... anyway, since my various cars take oddball amounts of oil and I need to top things off sometimes, I have ended up with a leftover 1.5qts of 5w-20 Mobil-1 and 2.5 qts of 5w-20 full synthetic Valvoline. I thought, "I'll go get some 0w-20, use the two leftovers and make up the difference with the 0w-20". The truck takes 5.5 qts or so at oil change.

But going online, articles and people seem to be super anal, like you can't mix weights or brands without destroying your engine, or doing some chemistry experiment in your engine with unknown results. I find this hard to believe. Is it really the case that if you are on a road trip and need to top off, that you are risking your engine if you can't find the same weight and brand/type as you originally used? Would the engineers at these companies not make their oils inert enough that they could operate in the real world where people are likely to mix?

I'm not poor or anything, but throwing away all my scraps of oil seems like a waste. I only need so much for chain lube and lawn equipment.
 
I’ve definitely mixed oils before. Never seen a difference before. People that argue oil are a unique breed of weird. The manufacturers have a broad range of weights depending on the environment the vehicle lives in.
 
Mixing brands is definitely not a problem. It does dilute the additive package of each one, IF the other doesn't have the same additive. Probably not much of a concern, IMO.

I stick with just two brands of oil, myself, and rarely ever mix them due to having plenty on the shelf.

I wouldn't be afraid to run the mixture of weights in AZ. But I don't know why the Toyota engine needs such a lightweight oil as well as others nowadays. I know that fuel economy is a factor, but I don't know why you couldn't mix 0 with 5 weight. Should just make it a 2.5 to 3 weight. :dunno:
 
Well I have mixed oil brands and weights.

As for the 5w20 verses 0w20 in a Toyota, personally I wouldn't do what you are proposing.
The cam timing mechanism needs that thin oil.
My wife's 2016 Scion TC specs 0w20. One summer oil change I did 5w20 and right away got check eng light and cam timing codes. Car was very low mileage at the time less than 20k.
Put 0w20 codes went away.
 
centexk5 said:
People that argue oil are a unique breed of weird.
Click to expand...
I resemble that, somewhat. :haha:

I don't argue about oil, but I have found proof of how different brands are better by watching oil temperatures, seeing the inside of an engine get cleaned up, oil consumption and oil sample results.
So I am biased, but I don't have time to argue about oil. :D
 
One theory is that manufacturers push the thin oil to scrape by the MPG requirements. They don't really care whether you make it to 200K+ or not.
 
Wes Harden said:
Well I have mixed oil brands and weights.

As for the 5w20 verses 0w20 in a Toyota, personally I wouldn't do what you are proposing.
The cam timing mechanism needs that thin oil.
My wife's 2016 Scion TC specs 0w20. One summer oil change I did 5w20 and right away got check eng light and cam timing codes. Car was very low mileage at the time less than 20k.
Put 0w20 codes went away.
Click to expand...
This is very interesting to me because my wife's van is throwing cam related codes and I had a theory that it could be related to me ignoring the thin oil recommendation. Now I have more hope that it could really be the case.
 
Wes Harden said:
Well I have mixed oil brands and weights.

As for the 5w20 verses 0w20 in a Toyota, personally I wouldn't do what you are proposing.
The cam timing mechanism needs that thin oil.
My wife's 2016 Scion TC specs 0w20. One summer oil change I did 5w20 and right away got check eng light and cam timing codes. Car was very low mileage at the time less than 20k.
Put 0w20 codes went away.
Click to expand...
That's great information!
Experience is very valuable. I've never tried that on one of these little engines.
 
Wes Harden said:
Well I have mixed oil brands and weights.

As for the 5w20 verses 0w20 in a Toyota, personally I wouldn't do what you are proposing.
The cam timing mechanism needs that thin oil.
My wife's 2016 Scion TC specs 0w20. One summer oil change I did 5w20 and right away got check eng light and cam timing codes. Car was very low mileage at the time less than 20k.
Put 0w20 codes went away.
Click to expand...
Agree. I tend to stay with the Manufacturers recommendation as a general rule. Mix in a pinch.
 
6872xtc said:
That's great information!
Experience is very valuable. I've never tried that on one of these little engines.
Click to expand...
While I most certainly agree with Wes and others about respecting the OEM’s viscosity ratings - one thing to consider is that ( for example the Yota 3.5 V6 2GR-FSK engine ) some of these motors are shared with other applications ( such as Lotus’ ) and carry a heavier weight rating since they are intended to be run all in balls out type of driving style.
In this case a 5W20 is called for on that same 2GR-FSK.
Since I live along the Gulf Coast where the asphalt damn near melts in the summer I use the 5W20 with no worries . Also, the 1FZ-FE 4.5 DOHC in my old FZJ-80 Land Cruiser called for 5W20 but the same motor in Australia applications called for 20W50.
I know of many others that have racked up 250,000+ on these 1GR & 2GR motors while running 5W20 and no ill side effects.
Now that I have said this if I lived in a cooler climate I would run the thinner oils with no worries as directed by the slide-ruler minded folks at Toyota.
Just something to think about…
 
Mastiff said:
One theory is that manufacturers push the thin oil to scrape by the MPG requirements. They don't really care whether you make it to 200K+ or not.
Click to expand...
That’s my thought, based on chasing CAFE standards. As the recommended weight can change just by one model year, same engine, seems fishy.
 
LOL
There sure is a line that was crossed with engines VS oil.

Flat tappet you need all the dinosaur vitamins plus some. Weights? Whatever.

New engines are picky little bitches. I wonder if that engine code is just to complain about the oil, not an actual problem.

My old ‘01 3.0 Camry. OMG the suicide concoction of oils that thing got when I changed it myself. Full/semi/dyno/ATV oils…. Didn’t care. LMAO
 
If you are running any engine that uses controlled oil pressure to control valve timing, you'd best stick with recommended oil weight. Some of them are really picky.
Personally I think its stupid to design an engine that the oil viscosity is that critical, but I have seen it happen.

Now if you want to go way back, at one time it was very unadvised to mix or even change brands of oil. I'm talking about the 1950s. Oil chemistry was pretty much the wild west back then. Everybody had their own idea of what was best, and would sometimes put in fancy sounding additives just for the bragging value.
There were at least two brands of oil that did not play well together. You add a quart of one to a crankcase filled with the other, and the result was..........not oil.
I suspect that there were more than two brands, because as a kid, I heard at least three mixes that were supposed to be fatal.

But, what is worse than that, is mixing non-detergent with high-detergent. One quart of HD in a high mileage engine that has been run with ND its whole life is pretty much a death sentence.
I saw it happen. The engine was running fine, used about a quart between changes. It was on a Jubilee Ford tractor that was about 20 or so years old and had been worked hard. ND oil its whole life.
One quart of Chevron HD, and it was toast in about 2 hours. Not even rebuildable.

BTW, I have heard all the arguments about ND vs HD in older engines. The only time you want ND is in an engine with no oil filter.
Like the old Beetles. With HD, all the dirt, sludge, blowby, just stays in suspension going round and round through all the bearings. With ND, it settles out into sludge and coats the inside of the crankcase. Not an ideal situation, but at least its not wearing the bearings.

J.
 
I am guilty of mixing oils, usually when I need a quart and have a leftover. Doesn't bother me, especially when an oil change is coming up soon.
I also run 20w50 in the dune buggy, it leaks out slower!
 
Sadly, I switched to the 0w20 in the wife's van and it's still giving the code that I thought might be related.
 
I was working at a Jeep dealer when the JK wrangler was introduced with the 3.8 V6 from the minivan line. In the vans it called for 10w30. In the Jeeps it called for 5w20, guess which one had oil consumption issues? That was the manufacture trying to get better MPG numbers. I agree with others though, if oil controls valve timing or cyl deactivation such as a DOD engine you better run the correct weight.
 
The 350 in my '85 K20 gets whatever is the cheapest when I am at the gas station, filling up oil and checking the gas.

Martin
 
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