Oil and Texas heat!

[MikeV]

During the Summer months in Texas, when I drive my '52  Dodge 1/2 pickup, my oil pressure really gets low (15to20psi) while at  idle say at a red light. While driving along at 50 to 55 mph, my  oil pressure is good around 40 to 45 psi. I'm using a straight 30 wt oil, so I'm thinking that maybe I should run a higher viscosity oil in the Summer. I'm curious what other flat head six guys are running in their trucks in the way of oil. I know there are quite a few trucks like mine in the Midwest. I would appreciate any comments. 

Thanks!

Mike

 

 

[Reg Evans]

Your oil pressure sounds pretty normal.  I run Delo 15-40 in my rebuilt 251 with approx. 25K since the rebuild.

 

[knuckleharley]

1 hour ago, MikeV said:

During the Summer months in Texas, when I drive my '52  Dodge 1/2 pickup, my oil pressure really gets low (15to20psi) while at  idle say at a red light. While driving along at 50 to 55 mph, my  oil pressure is good around 40 to 45 psi. I'm using a straight 30 wt oil, so I'm thinking that maybe I should run a higher viscosity oil in the Summer. I'm curious what other flat head six guys are running in their trucks in the way of oil. I know there are quite a few trucks like mine in the Midwest. I would appreciate any comments. 

Thanks!

Mike

 

 

I run 30 wt non-detergent in my stock non-rebuilt flat 6 in the winter,and 40 wt non-detergent in the summer. 40 wt non-detergent can sometimes be hard for me to find locally,so I buy it by the case from Amazon.

[Worden18]

Mike, your oil pressure is normal.  As your engine heats up the oil thins out and the pressure will drop some.  I have 150 miles on a total rebuild and my pressure is exactly the same as yours at idle and at 55mph.  My old timer friend told me once that even 2lbs of pressure is okay; that means oil is flowing through 

That 2-5lbs at idle is what my pre-rebuild engine had for pressure.  Hey, it didn't blow up 

[MikeV]

Thanks Reg Evans, knuckleharley, and Worden 18 for the replies!!

I've got 800 miles on my 251 Cu engine since rebuild and the  oil pressure issue always bothered me.I guess if it hasn't locked up on me by now, it's just find!

thanks guys!

[JBNeal]

I ran straight 30 for years in the Texas heat, then did some reading and switched to 10W30 cuz I used that weight in a lot of other machines I was running and was buying it in bulk anyway.  There was no apparent change in pressure and I always had some on the shelf

[knuckleharley]

6 hours ago, JBNeal said:

I ran straight 30 for years in the Texas heat, then did some reading and switched to 10W30 cuz I used that weight in a lot of other machines I was running and was buying it in bulk anyway.  There was no apparent change in pressure and I always had some on the shelf

You don't run the heavier weight oil to gain oil pressure. You run it because it does a better job of taking heat away from your bearings. It will sometimes appear to add oil pressure,but that's only when the engine is cold. Heavier oil does a better job of absorbing heat than lighter oil,and in worn engines can also reduce oil burning.

This is true with non-detergent oil. For all I know some of the additives in high detergent oil may negate some or all of advantage heavier weights have in non-detergent oils.

 

 

 

[Dan Hiebert]

Ditto.  We bought our D24 near El Paso, lived there for 5 years, then south east New Mexico for another 5 before moving north.  Meaning we drove our D24 regularly in that southwest heat.  I've always used plain old SAE 30, and had the exact same oil pressure readings as your truck does.  This forum didn't exist back then, but lots of face-to-face research with old timey mechanics, who worked on these cars and trucks in the region when they were new satisfied me that what you describe is normal.  The D24 still did that in MI, NY, and now up here in Maine...just takes it a little longer to warm up. 

[JBNeal]

To avoid  another argument about engine oil, I will point out that I did some reading, and I weighed the risks and benefits of going to 10W30.  I operate my flatheads in light duty use:  once or twice a week, with mostly the weight of the truck as its load, and at low engine revs.  Even if I had a daily driver, I would stick with the 10W30 because it was presumably brought to market to be backwards compatible with its use of detergents and stabilizers.  I'm a little confused at the heat exchange argument as the Texas heat makes 10W30 act like straight 30 anyways...therefore, it was cheaper for me to buy 10W30 in bulk since it would act like straight 30 almost year round.  If I were to operate my flatheads in heavy duty use, I would probably switch to the 15W40 that I use in my Cummins, which is the other oil grade that I buy in bulk.  But I have the Cummins as the workhorse so that I can use the flatheads for fun, so it is cheaper for me to run 10W30 than 15W40.  No matter which grade used, keeping the levels nominal and changing as required are paramount  

[The Oil Soup]

Here is an excellent exchange on oil. Blues4u chimes in and really knows his stuff! My truck with 60k original miles runs the same pressures as described by the OP. https://www.jalopyjournal.com/forum/threads/zddp-again.1057854/