Edge 5W-50 in an engine specced for 20W-50

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1,555
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I've been intrigued for a little while about some of these heavy, huge viscosity spread oils.

I've used a lot of 20W-50(generally VR-1 or GTX), and as anyone knows it flows like molasses when cold. I know cold flow out of the bottle isn't a great measure, but it seems to me that, especially at lower cold start temperatures, it could take its time getting to where it needs to be. I've personally seen the oil pressure rise somewhat reluctantly in an engine with 20W-50 when it was say in the 30s, where it comes up almost immediately at warmer temperatures.

I'm aware of two 5W-50s on the market-Castrol Edge and Mobil 1. Both spec enough zinc that I'm not worried about them for flat tappets. I have a half case of Edge sitting here, and I'm kind of itching to dump it in my MG. Mine isn't a garage queen-I drive it as long as there's not salt on the roads-and still like to start and work on it even when there is. It seems like this oil would be a game changer.

For reference, this is a freshly rebuilt and consequently fairly "tight" engine(rebuild=teardown, bore cylinders, grind crank, put together with new bearings, pistons, rings, cam, etc) that I'd guess has about 800 miles on it. I'm due for a break-in oil change now that it's done some serious miles(the shop changed it after the initial 30 minute stationary break-in and then supposedly after driving it a bit) and am wondering about putting this in vs. just a good 20W-50.

Any thoughts on this? My biggest fear would be that it would be TOO thin at when cold.
 
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Put some Motor Honey in it and listen to that engine hum like a 🐝.

1614173961306.jpg
 
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I've been intrigued for a little while about some of these heavy, huge viscosity spread oils.

I've used a lot of 20W-50(generally VR-1 or GTX), and as anyone knows it flows like molasses when cold. I know cold flow out of the bottle isn't a great measure, but it seems to me that, especially at lower cold start temperatures, it could take its time getting to where it needs to be. I've personally seen the oil pressure rise somewhat reluctantly in an engine with 20W-50 when it was say in the 30s, where it comes up almost immediately at warmer temperatures.

I'm aware of two 5W-50s on the market-Castrol Edge and Mobil 1. Both spec enough zinc that I'm not worried about them for flat tappets. I have a half case of Edge sitting here, and I'm kind of itching to dump it in my MG. Mine isn't a garage queen-I drive it as long as there's not salt on the roads-and still like to start and work on it even when there is. It seems like this oil would be a game changer.

For reference, this is a freshly rebuilt and consequently fairly "tight" engine(rebuild=teardown, bore cylinders, grind crank, put together with new bearings, pistons, rings, cam, etc) that I'd guess has about 800 miles on it. I'm due for a break-in oil change now that it's done some serious miles(the shop changed it after the initial 30 minute stationary break-in and then supposedly after driving it a bit) and am wondering about putting this in vs. just a good 20W-50.

Any thoughts on this? My biggest fear would be that it would be TOO thin at when cold.
There is no such thing.
Another good option, not as good when cold, but better than 20W50 is Mobil1 15W50 which has ZDDP at 1,300ppm.
 
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I would probably go another oil change or two before switching to synthetic. Last I checked the major oil manufacturers, some at least, mentioned waiting until after break-in to siwtch to synthetic for non factory engines; field overhauls.

I would lean towards the M1 15w-50, that is my go to oil for most of the oldies in my fleet. That said, the M1 5w should be fine, that is what I use in my diesel Rover w/ 5k on the rebuilt motor. You have a 'real' oil pressure gauge, that will give you your answer (y)

Pic of the car please.
 
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Middle of Iowa
Use the listed viscosities for each oil, and a plotting tool...then look at the coldest temperature you will be starting at. Then decide if that difference is enough to matter for your location and use case.

If you live in Florida...probably won't matter
If you live up here, we saw -23F the other day...might make a difference between starting or not (I use 5W-40 in everything, and my cars started fine)

I wrote a white paper on how to do it, I could probably send you (if I can find it) if interested.
 
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South Carolina
You should be using 10w-40 in your MG. That is what my '62 Sprite and '70 MGB called for. To answer your question, 5w-40 year 'round. I'm using 0w oil in my vehicles and I live in South Carolina!

EDIT: In a "tight" rebuild, why do you want such a high vis oil?
 

bunnspecial

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Thanks everyone for the responses. It sounds like, break-in aside, there should be any real issues with this oil. If draining the sump when hot is any indication, hot 20W-50 drains faster than I imagine even cold 5W-50 would. There again, I know pour speed isn't the end-all-be-all, but it's something observable.

As for temperatures, we were in single digits last week as highs and negative lows, and are at 55º now. We can hit 100º in the summer. That's a fairly normal range.

Also, I see recommendations for 15W-xx. Any particular reason why that and not a 5W-xx?

You should be using 10w-40 in your MG. That is what my '62 Sprite and '70 MGB called for. To answer your question, 5w-40 year 'round. I'm using 0w oil in my vehicles and I live in South Carolina!

Not sure what reference you're using, but here's a factory table for the MGB. Note the plethora of recommendations for 20W-50 here.
mgb lubricants.jpeg


In the MG community, 20W-50 is the default recommended oil grade even now. Given that there's quite a bit of factory information supporting 20W-50, I think that's a safe way to go.
 
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5,156
Location
Midwest
I've been intrigued for a little while about some of these heavy, huge viscosity spread oils.

I've used a lot of 20W-50(generally VR-1 or GTX), and as anyone knows it flows like molasses when cold. I know cold flow out of the bottle isn't a great measure, but it seems to me that, especially at lower cold start temperatures, it could take its time getting to where it needs to be. I've personally seen the oil pressure rise somewhat reluctantly in an engine with 20W-50 when it was say in the 30s, where it comes up almost immediately at warmer temperatures.

I'm aware of two 5W-50s on the market-Castrol Edge and Mobil 1. Both spec enough zinc that I'm not worried about them for flat tappets. I have a half case of Edge sitting here, and I'm kind of itching to dump it in my MG. Mine isn't a garage queen-I drive it as long as there's not salt on the roads-and still like to start and work on it even when there is. It seems like this oil would be a game changer.

For reference, this is a freshly rebuilt and consequently fairly "tight" engine(rebuild=teardown, bore cylinders, grind crank, put together with new bearings, pistons, rings, cam, etc) that I'd guess has about 800 miles on it. I'm due for a break-in oil change now that it's done some serious miles(the shop changed it after the initial 30 minute stationary break-in and then supposedly after driving it a bit) and am wondering about putting this in vs. just a good 20W-50.

Any thoughts on this? My biggest fear would be that it would be TOO thin at when cold.
You could split the difference use Mobil 1 15w-50. It's readily more available and available in 5qt jugs at walmart.
 
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17,036
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Upper Midwest
Thanks everyone for the responses. It sounds like, break-in aside, there should be any real issues with this oil. If draining the sump when hot is any indication, hot 20W-50 drains faster than I imagine even cold 5W-50 would. There again, I know pour speed isn't the end-all-be-all, but it's something observable.

As for temperatures, we were in single digits last week as highs and negative lows, and are at 55º now. We can hit 100º in the summer. That's a fairly normal range.
Of course a hot 15W-50 drains faster than cold 5W-40, did you read any of the responses in this thread? That isn't what you were asking about.

Here is a graph of the viscosity of a typical 15W-40 plotted against a typical 5W-40 (in Celsius). What do you see?

Again, no oil regardless of the winter rating is ever too thin in cold temperatures. If it isn't too thin when hot it won't be too thin when cold. In fact it will be massively thick.

Capture.PNG
 

bunnspecial

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Of course a hot 15W-50 drains faster than cold 5W-40, did you read any of the responses in this thread? That isn't what you were asking about.

I'm not sure why the hostility in this response.

Of course I read every response, and in fact multiple times. I always do when I ask a question and get multiple answers.

My "draining" comment was an observation I was making in reference to how oils behave at engine temperatures and not their cold viscosity.

Thank you for the chart. That is a lot of useful information, and I want to spend some time looking at more information like that.
 
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Paradise of Florida
Oil pressure and typical temps? Does it really need a 50 grade?

I would have no problem using a 15w50, 10w50, or 5w50 oil in that engine.

There are plenty of good motorcycle oils in the 40 and 50 grades, conventional or synthetic, that would be good choices(modern blends and good z/p dosage).
 
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South Carolina
View attachment 46747

In the MG community, 20W-50 is the default recommended oil grade even now. Given that there's quite a bit of factory information supporting 20W-50, I think that's a safe way to go.
I'm not sure how new (old) your chart is. Back in the 60's/70's when I had my Austin's and MG's any of your 50's were unheard of and unavailable here in the US. 10w-40 was very popular and what was recommended and used. Maybe your chart is from the EU and not one for the US market? Anyways, I used 5w-30 (Mobil1) in my MGB and ran it back and forth to San Diego several times to visit a friend. Ran great and used no oil.

EDIT: I, also, worked at a Jaguar/MG/Datsun dealer back then and we put bulk 10w-40 in everything.
 

bunnspecial

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I'm not sure how new (old) your chart is. Back in the 60's/70's when I had my Austin's and MG's any of your 50's were unheard of and unavailable here in the US. 10w-40 was very popular and what was recommended and used. Maybe your chart is from the EU and not one for the US market? Anyways, I used 5w-30 (Mobil1) in my MGB and ran it back and forth to San Diego several times to visit a friend. Ran great and used no oil.

xW-50 oils were certainly around when the car was in production. Of course I can't vouch for what was done in dealerships, but the 20W-50 spec is easy to find in lube charts. It's in the 73 workshop manual, and I've also seen it specced in oil charts and publications from BMC(i.e. before the merger to BL). The use of 20W-50 is widely supported both in period and current literature and practice, so your "shouldn't be using" is a hard statement for me to get behind.
 

bunnspecial

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I would probably go another oil change or two before switching to synthetic. Last I checked the major oil manufacturers, some at least, mentioned waiting until after break-in to siwtch to synthetic for non factory engines; field overhauls.

I would lean towards the M1 15w-50, that is my go to oil for most of the oldies in my fleet. That said, the M1 5w should be fine, that is what I use in my diesel Rover w/ 5k on the rebuilt motor. You have a 'real' oil pressure gauge, that will give you your answer (y)

Pic of the car please.

I know you keep asking for pictures. It's nice today, and I'm hoping to fit the new(original) front bumper I just got to replace the awful reproduction one on it. I'll post a "prettied up" picture once that's done.
 
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xW-50 oils were certainly around when the car was in production. Of course I can't vouch for what was done in dealerships, but the 20W-50 spec is easy to find in lube charts. It's in the 73 workshop manual, and I've also seen it specced in oil charts and publications from BMC(i.e. before the merger to BL). The use of 20W-50 is widely supported both in period and current literature and practice, so your "shouldn't be using" is a hard statement for me to get behind.
Where did I say that?

The '73 service manual was printed in England where w50 was available. And, yes, what you are stating was true for vehicles in England. I don't know if you were around or driving in '73 but 20w-50 was like finding Hen's teeth back then in the US. If you are getting advice from this, or other forums, on old British cars make sure the folks giving advice were wrenching on them back then.

Also, I still would like to know what the obsession is about using such a heavy oil in a "tight" engine build?
 
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20w50 was developed as a band aid for the early Mini’s oil shearing issues and eventually became a bread and butter oil in europe

From Doug Hillary:

“the 20W-50 viscosity was formulated by Duckhams in 1958-9 purposely for the BMC Austin/Morris "Mini". It needed this because of the high permanent shear rate of the lubricant solely due to the combined engine/gearbox

The BMC "A", "B" and "C" engines in most applications used 20W-20 or 20-30 viscosities Worldwide with excellent results - as did most other British engines of the 1950-60s. 10W-30 was also extensively used in this period. The 20W-50 viscosity quickly became the "fix-it" lubricant for high oil consumption due to wear and neglect - and because of extensive advertising by both Duckhams and Castrol

Other Euro OEMs didn't quickly jump onto the 20W-50 viscosity - many never did!”
 
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bunnspecial

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If you are getting advice from this, or other forums, on old British cars make sure the folks giving advice were wrenching on them back then.

Give John Twist a call and ask him what oil he put in every MG that came through University Motors in Grand Rapids, MI from 1973 to 2018 when he was in business. Before opening that shop, John spent two years learning to wrench on MGs at University Motors in London. Those are pretty darn good credentials to me. While you're at it, ask what has been in his MGA since he rebuilt it in 1980. Call and talk to Dick Moritz up in Philadelphia, who has built hundreds of B series engines ranging from stock to full blown race motors(my build is based on his "Street Performance" formula, and he supplied a lot of the parts), and ask what he tells every single customer to run in their engine, plus every single car he's worked on. Back when I had my Marina, which also uses a B engine, I spent a lot of time talking to Skip Harris down in Arkansas, who ran the service department of an Austin/Triumph/MG dealership in the early 70s. I can name drop other folks who I know personally and have been wrenching on MGs and other British cars when they were still widely available in the US.

I'm asking here about one SPECIFIC oil because I desire one SPECIFIC property(better cold cranking). You're the only person I've ever had tell me so adamantly that 20W-50 wasn't a proper choice for this engine. I'd sleep easy running nothing but that, I'm just looking at other xW-50 options.
 
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