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Please, let's not get into a big debate on viscosity, additives, etc. 3 years now I've been running 15-40 with no issues. I picked up a jug today and found some 20-50 on sale so I bought it. I tried reading up on the 20-50 and somewhere it was said it was the last resort for a failing engine. Also could make the oil pump work harder and cause issues. So I was hesitant to use it. Today I went for an hour or more cruise around the city. Temperature outside was a cool 64 F. Engine temp was perfect. If I had to guess from the oil gauge, I eventually cruised at about 20-25 psi at best and the usually singe digit psi at stop lights.  

Should I attempt to try the 20-50 or am I just asking for trouble? It will eventually get warmer out....I hope! I still have the receipt so returning it will be no problem.

Thanks Mark

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5 minutes ago, Summershandy said:

Please, let's not get into a big debate on viscosity, additives, etc. 3 years now I've been running 15-40 with no issues. I picked up a jug today and found some 20-50 on sale so I bought it. I tried reading up on the 20-50 and somewhere it was said it was the last resort for a failing engine. Also could make the oil pump work harder and cause issues. So I was hesitant to use it. Today I went for an hour or more cruise around the city. Temperature outside was a cool 64 F. Engine temp was perfect. If I had to guess from the oil gauge, I eventually cruised at about 20-25 psi at best and the usually singe digit psi at stop lights.  

Should I attempt to try the 20-50 or am I just asking for trouble? It will eventually get warmer out....I hope! I still have the receipt so returning it will be no problem.

Thanks Mark

your engine was designed for straight 20 in cold weather, straight 30 in warm weather, i don't see any problems with you using the 20-50.

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20w50 is great in cars that were designed to run 20w40. The Pontiac was intended for thinner oil. That said, I run 10w30 in my Pontiac 6, but in really hot weather (105-106F), when the coolant is also near the boiling point, it loses pressure pretty badly. In the hottest part of the summer I change it over to 20W50. 15w40 isn't really enough of a change to do the trick.

 

FWIW lighter is better if you can get away with it because it gets oil on things faster when you start the engine. IMHO just use the 20w50 in the hottest part of the year.

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15 hours ago, Bloo said:

In the hottest part of the summer I change it over to 20W50.

 

I'm think that's what I'm going to try. Just to see if there is any difference in pressure readings. But I'll stick with what I've been using as our summer's don't get as hot as many of you "down south".

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Yours is a very nice looking Pontiac and I especially like the color. 

I know mine is not a Pontiac but my straight 8 in a 30 DeSoto is getting a little noisy. Switched to 20-50 along with STP. :hide:

The oil pressure is much better and the engine sounds better. It didn't smoke so no change there. Mostly piston slap. The thicker oil will tend to cling to parts better than thin oil and I have noticed the engine is quieter when starting. I would not run this in the winter or temps below 40 degs. 

  Back in the 60's and 70's we would coat all engine parts with a 50-50 blend of motor oil and STP when doing an overhaul. Never had a problem. 

This is just my 2 cents on the subject. Your mileage may vary. 

 

Edited by Fossil (see edit history)
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27 minutes ago, Fossil said:

Yours is a very nice looking Pontiac and I especially like the color. 

 

Funny thing is many people say the same thing! It may not be the original shade of Biloxi Biege but is still eye catching. 

 

27 minutes ago, Fossil said:

I would not run this in the winter or temps below 40 degs. 

 

At 40 degrees the car would be stored away for the winter. 

 

27 minutes ago, Fossil said:

This is just my 2 cents on the subject

 

Any cents is worth money...I love hearing opinions on related subjects! How else would I learn?

Edited by Summershandy (see edit history)
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  • 2 months later...
On 6/15/2020 at 11:07 AM, Summershandy said:

 

Funny thing is many people say the same thing! It may not be the original shade of Biloxi Biege but is still eye catching. 

 

 

At 40 degrees the car would be stored away for the winter. 

 

 

Any cents is worth money...I love hearing opinions on related subjects! How else would I learn?

Aw C'mon. 40 is just a nice fall morning up here. 

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9 hours ago, Oldtech said:

Aw C'mon. 40 is just a nice fall morning up here. 

LOL true....but it's usually followed by snow then our city plasters it with road salt. Something this old girl ain't ever gonna see! I can't even take it out early spring because the roads are covered in white dust. I wait until the rainy season or road cleaning before it comes out of the cocoon

On the subject, I never did get around to changing the viscosity. A fresh jug of 20/50 sits in the garage until next year's oil change. Seems the engine quite enjoys cruising around at 18 degrees C or 64.4 F  

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