Oil weight

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MWalker
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Oil weight

Post by MWalker » Tue Jun 16, 2020 4:33 pm

No, this isn’t a “what kind of oil should I use?” post. I use Pennzoil 10w-30. I have some jugs of 5w-20 which I bought to use in a modern Mercury that I later sold. If I mix the two, will I have 7.5w-25, or doesn’t it work that way?

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CudaMan
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Re: Oil weight

Post by CudaMan » Tue Jun 16, 2020 4:48 pm

If they're both the same brand (and probably even if they're not), your theory about mixing them is probably correct. I do it all the time if I end up with some "orphan" oil. It goes into the jug that eventually ends up in the Model T. So far, no harm no foul. :)
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MWalker
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Re: Oil weight

Post by MWalker » Tue Jun 16, 2020 5:12 pm

Yes, they both are Pennzoil. I hate to throw out 2 or 3 5-quart jugs of oil


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Re: Oil weight

Post by tiredfarmer » Tue Jun 16, 2020 5:49 pm

I was told by my dear ole Dad, never mix oil. Why I never asked, I figured that he was older and new why.


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Re: Oil weight

Post by R.V.Anderson » Tue Jun 16, 2020 8:59 pm

I've heard that it's because different brands of oil have possibly incompatible additives that react and cause them to permanently leach out of the oil, leaving a separated portion (up to 1/3) that has no lubricating qualities whatever. I have never confirmed this with a petroleum engineer but that's what I've heard.


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Re: Oil weight

Post by Wayfarer » Tue Jun 16, 2020 9:25 pm

my understanding is that all oils rated by the SAE are required to be mixable

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Re: Oil weight

Post by Steve Jelf » Tue Jun 16, 2020 11:46 pm

A very expert Model T mechanic told me he uses 15W-40. Another, who probably drives more than the rest of us combined, uses Kendall 20W-50. (I don't know why Kendall.) Ford recommended 20W. But 5W-20 is NOT the same as 20W. I would definitely not mix in the 5W-20 at 50/50. Maybe half a quart at each oil change, if any at all.
Oils Chart.jpg
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Re: Oil weight

Post by HalSched » Wed Jun 17, 2020 12:09 am

I don't know what this has to do with anything, but when I was a kid I used drain oil from a fleet of farm tractors and trucks. I drove the T a lot too. I don't think any of the farm vehicles had oil filters and as I recall the oil was VERY black.

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Re: Oil weight

Post by TRDxB2 » Wed Jun 17, 2020 1:25 am

extracted this info from this site https://mechanics.stackexchange.com/que ... -viscosity ( was posted on it in NOV 2018)
From the Chevron.com site: "Can I mix different viscosity grades of motor oils?" "Yes. It is always advisable to not mix motor oil brands, however, different viscosity grades of the same brand motor oil are compatible. Be aware that mixing viscosity grades will turn out a product that is different in viscosity than either what was originally in the engine or what was added."
From Shell.ca: "If you mix viscosity grades such as a 5W30 low-viscosity oil and a 10W40 higher-viscosity oil, it is reasonable to expect that the resulting product will have viscosity characteristics which are thicker than the 5W30, but thinner than the 10W40. This change does not reflect incompatibility - it's simply a re-balancing of the viscosity characteristics. In all other ways, the product should work as expected. But there's absolutely no danger about incompatibility resulting from mixing engine oils," Miller says. "We've tested all of our grades and brands, and we haven't observed any problems."
From Mobil1.com: "For our customers to choose a viscosity grade, we recommend they follow the engine manufacturer's recommendations as indicated in their owner's manual. There is no need to mix two Mobil 1 viscosity grades when one will do; however, we see no problem mixing different SAE grades of Mobil 1 Tri-Synthetic series motor oils."
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Re: Oil weight

Post by D Stroud » Wed Jun 17, 2020 6:28 am

As for a T, I doubt it would care much at all if was mixed, as long as there was some kind oil in the crankcase. ;) ;) Dave
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Re: Oil weight

Post by Steve Jelf » Wed Jun 17, 2020 8:41 am

...as long as there was some kind oil in the crankcase.

Or passing through the crankcase on its way to the floor.
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Re: Oil weight

Post by MWalker » Wed Jun 17, 2020 8:51 am

Thanks to everyone for your input. I especially like Frank Brandi's post, which seems to have quite a bit of factual and helpful information.


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Re: Oil weight

Post by Bud Delong » Wed Jun 17, 2020 9:01 am

Is there any written proof that Henry said anything other than a light weight high grade machinery oil. In 1955 when many of Ford people of the times were still with us the book Tin Lizzie by Stern said SAE-10. Then as today much depended on where you lived and the temp and season.Oil is cheap,engines not so much!!!! Bud. :D

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Re: Oil weight

Post by Squirrel » Wed Jun 17, 2020 9:10 am

Pictures of old oil cans. Draw your own conclusions.

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light.jpg
medium.jpg
medium.jpg (13.49 KiB) Viewed 4955 times
heavy.jpg
heavy.jpg (45.5 KiB) Viewed 4955 times


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Re: Oil weight

Post by 23ford » Wed Jun 17, 2020 7:43 pm

We need Rich Chillingworth to comment on all this as he is a petrol eingeer....just sayin :mrgreen:


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Re: Oil weight

Post by MWalker » Thu Jun 18, 2020 8:56 am

I see a post by "Squirrel" above. I recognize you from the HAMB; surprised to see you here. :)


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Re: Oil weight

Post by J1MGOLDEN » Mon Jun 22, 2020 5:45 pm

When you get that all figured out, the can markings, grading and contents are soon all going to change again.

I read someplace that the early engine oil was not much thicker than kerosene or automatic transmission fluid.

That would not work well today, as any drip is frowned on!


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Re: Oil weight

Post by ModelTWoods » Mon Jun 22, 2020 6:15 pm

No not oil weight : Oil type ! I've read discussion on the forum where using Shell Rotella 15W-40 diesel oil was discussed. Any merit to it?
Last edited by ModelTWoods on Tue Jun 23, 2020 12:14 am, edited 1 time in total.


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Re: Oil weight

Post by Bud Delong » Mon Jun 22, 2020 6:30 pm

I use a lot of Rotella 15-40 in many engines but not in our stem wind model T"s :D Bud.

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