Is 20W-50 too heavy for my 340?

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340inabbody

340inabbody

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I have some 20W-50 VR1 “High Zinc” in my shop and am planning an oil change. Is this too heavy?

Information:

Flat tappet 340
High compression 12:1?
Older engine oil pressure was on the lower side if I recall correctly maybe 30 psi but don’t recall what oil was used.
Lives in Phoenix and it’s getting HOT!

If not what do you recommend?

Thank you!
 
Any oil viscosity question should be met with another question. What are the clearances in the bottom end? I realize not everyone has this information but selecting a viscosity without it is a guess. The VR1 is good ****, run it, but it might take some experimenting with a few oil changes at different viscosities to get what you’re after.
 
You are fine as long you don’t plan on driving it in the winter which I’m sure you’re not.
 
Lol I don’t even know what cam is in it! I probably used this oil before but good to know that it’s got some thumbs up here lol
 
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Been using VR1 20w50w in my 360 for about 30 years. My Dad used it (Castrol GTX) in his LA 360 too- forever
 
I use 10W30 since 2004.
My only gauges are what came on the factory rally dash.
I don't have an aftermarket oil pressure gauge, so I have nothing to worry about. Just Like I don't have an aftermarket temp. gauge, so again no worries. Without worries, I can just driiiive it, lol.
well, to be truthful, the 367 is wearing a deep pan and a high-volume oil-pump.
 
TF360 said:
forever
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My brother used 20-50 in EVERYTHING, lawn mowers, tractors, all his cars and trucks even during the dead of winter in PA. All his stuff never had a problem. I use it too in my older stuff and motorcycle. Motorcycle 20-50.
 
Definitely for a stock/older/worn out motor. But anything built recently, I’d go with the builders recommendation. Both motors I’ve had built in the past 10 years the builders(different for each build) recommended 10w30 full synthetic.
 
You could probably run 60W nitro racing oil in the Phoenix summer heat without issues in a 12:1 340, and that enviroment is one of the few times I'd consider the 20W50... I have ran 20W50 in some other engines and could tell it absorbed a little more power than 10W40 and it made about 15 PSI more oil pressure.
 
Really not a valid question. What oil weight were you running.. what was the oil pressure. If you were running 10/30 and all was fine, 20W50 could blow you off the scale.

Based on engine clearances, I run them all in my cars. You just need to nail down which one is right and stick with it.
oilpenngrade 002.JPG
 
I run 30wt straight in my 360. I've always ran this weight no issues. I have the 292 mopar cam and crane stiff springs. 340 X-heads. 3.91's out back. Car runs like a champ!
 
Forgot to mention 30wt Penn grade. Recently acquired Schaefers 30wt and will try it next oil change! Also in the past ran Vr-1 30wt no issues.
 
I buy LOTS of diesel oil when it's on sale (oil change in both my diesels, bye-bye 24 quarts)
I was given a couple cases of old racing oil, loaded with zinc. Trouble is, it's straight 50 wt.
So, in my flat tappet solid lifter 440, I use a mix of 10-40 diesel, and a couple quarts of 50 wt (out of eight)
I'm sure somebody will say it's a terrible mistake...... but it works for me.
(I save the thin watery synthetic for my late model muscle car that requires it).
Imo, bottom line? Run the 20/50.
 
33IMP said:
True, but not enough for me to worry about. I'd rather have really good oil pressure.
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I'll tell you what. I tried 20/50 in Vixen's slant 6 about a year or so ago, because I had some. It made the engine very difficult to idle when it was cold and you could FEEL it. I could feel less power going down the road. I was blown away, but that's the truth. I ran it for about a month when our next payday came around and changed it back to the Motorcraft semi synthetic 5/20 with Rislone ZDDP additive and it made a world of difference. Had anyone told me that story before it happened to me, I wouldn't have believed it.
 
33IMP said:
True, but not enough for me to worry about. I'd rather have really good oil pressure.
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Oh and with the 5/20, Vixen has 75PSI cold at idle and about 50 hot at idle. AS SOON AS you blip the throttle it zings right up to 70-75 when hot. So if the clearances are good, oil grade won't really matter.
 
I can believe that too thick oil can be felt easier in a slant than in a 500hp 440.
And I use the oil that I use for the same reason..... I have some. (Actually, quite a bit)
 
33IMP said:
I can believe that too thick oil can be felt easier in a slant than in a 500hp 440.
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Absolutely. If this little engine is 200HP, I'd be surprised. But the smiles per gallon it produces is off the charts.
 
33IMP said:
I'm just happier with nice thick oil, bracket racing in Vegas at 110° in the shade.
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I just cannot agree with fighting low oil pressure with a change in oil grade. But if it works, go for it. But it's not really "working".
 
I live in a hot climate & use 10w/60 oil. On a cold winters day, it flows like a '10' oil to get to the engine components quickly.
On a hot 40*+ C day, when I come off the freeway with a heat soaked engine, I have 30 psi at idle.......not 10.....
 
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