Mixing two oil wieghts

BruceMc wrote:
Yea, I just had to jump into the fray for the fun of it.
Correct, water isn't much of a lubricant particularly for these applications, for sure.

Yeah, me too! While hair is a lubricant, I certainly wouldn't use it in an engine!

I concur, mixing those weights wouldn't make a noticeable difference.

Lots of bored guys on this forum...

Mixing weights or brands will not have any adverse effects. Period! Although I would pretty much stay with in recomended specs as far as viscosity. If the vehicle calls for 0/20, 10/30 won't be a big deal. I run shell rotella T 15/40 in my old 87 going to the dump chev gasser pickup. It has over 200,000 miles on it & still running.

MEXICOWANDERER wrote:
Using multiple grades of oil can be a problem if different VII's viscosity index improvers get involved.

Sticking with a manufacturer's recommended viscosity is tough to beat.

Agree, but my comment was more to the fact that a different grade in a small quantity will only give you a small change in weight.

Using multiple grades of oil can be a problem if different VII's viscosity index improvers get involved.

Sticking with a manufacturer's recommended viscosity is tough to beat.

I remember when I was just a youth growing up on Long Island, the family owned a 1962 (?) Chevy station wagon with the blue flame six engine. If I remember correctly, it also had a 2-speed auto tranny (weird?). The engine developed an oil leak somewhere and I remember my father always adding oil. I don't know the viscosity, but it appeared to be a dark greenish color. Well, that engine went over 100k (good in those days).

I guess the reason the engine lasted so long was that it was undergoing a constant oil change! :B

Some years ago I spent some time with the guys that developed Mobil 1. They told flat and simle: You can mix weights, it is just a mathematical conversion. In your case, half 0w20 and half 5w20 will give you 2.5w20.
You can mix brands, it makes no difference.
More important, you can mix synthetic, dino or blend. I was surprised on this one and I asked for more explanation. Synthetic is a completilly different formulation than dino. One of them told me "How come you can buy a synthetic blend?" Their chief engineer told me to use any oil unless I will be in extreme temperatures. 5w20 can be replaced by 5w30 without much problem because 5w20 was formulated as a gas savings method.
So here is what I do in my rental fleet. I run 5w30 Mobil 1 in all gas engines (which call for 5w20 or 5w30) and 15w40 Mobil 1 in all generators.
All RVs have a bottle of 10w30 Mobil one in case they need to add to the engine or the generator.
I have had rental units with over 300K miles that didn't consumed oil and generators well over 3000 hours with no problems.
Hope it helps.

Think about it. How many people add a quart of oil (or more) to their crankcase having no idea of what oil (brand, age, mileage, type, viscosity, etc.) is already in there? Just be close. It happens all the time. Where are the broken engines? They don't exist.

Mix the oils and be done with it. Next time, buy the correct oil and change it per the schedule. Spend your time/worries on more important things. Google "BITOG" if you insist on obsessing about it. IMO, you can spend 1,000 hours at BITOG and know less about oil than you do now!

Chum lee

Yea, I just had to jump into the fray for the fun of it.
Correct, water isn't much of a lubricant particularly for these applications, for sure.

With the advances in lubrication and manufacturing, you are correct, there's no need for those older thick oils. We used to run either straight 30 wt or 10-40 in our vehicles then 10-30 became more common. I currently use 5-30 in our American vehicles, but the 2016 VW gasser is still an odd beast - it requires 5-40.

Per your comment regarding lifespan - in my late teenage years, I recall shopping for used cars. Anything that had 60-70K miles was considered "worn out", where 100K was pretty much unheard of. Again, you are correct - I regularly put around 200K on my vehicles before trading, and most of those have still had engines that didn't use a drop of oil. Other major things were failing, but the engines were just getting broken in..

Fun.

BruceMc wrote:
While uselessly adding to the cacophony, mixing weights is not an issue, particularly when they are that close.

[soapbox] What I'd like to say, however, if they keep manufacturing thinner oils, it'll soon be the same as water... might as well pour water into our engines! [/soapbox]

Well, except for water being a poor lubricant between the materials in use, there's nothing wrong with the thinner oils. Sounds like you're of the older generation that used heavier oils to help ameliorate the problems with large clearances and dissimilar metals common in engines of 50-60 years ago.

Subconsciously I have issues with the thin oils, but the clearances, and modern materials and design allow for, and sometimes mandate, the use of lower viscosity oils. Trying to run a 10 or 20 weight oil in the old engines of the 50's and 60's would have resulted in a very short lifespan. Now 200,000 to 300,000 miles is not in the least unusual with the engines of the last 20 years. That would have been unheard of with the engines of my youth.