Update. I checked the oil after it cooled and it was at the add mark so I put in a qt of 20-50 (all I had) and the pressure seemed to stabilize a bit, but it was a short trip. Will check on the ride home and report back.

Thanks also for the info on sender location. I will check that this weekend.

 

thanks merc225hp..sorry, in case you don't have a manual for the truck, think you can download info from the DIY section on here..good luck

 

Manual HERE...

 

Guys,

The pressure stabilized on the ride home so it appears to be either bad oil, the low level or a combination of the two that was affecting it. In either case, once I added the thicker new oil it acted exactly like the video Kejobe posted earlier. Will still do the manual pressure test this weekend to verify the gauge, but crisis seems averted for now.

Thanks again.

 

i wouldn't suggest using 20w-50 anymore. theres no reason, and honestly, its a little thick for the application.

 

Agreed on the viscosity. I am going to fill it with SAE30 as suggested in the manual and see how it goes.

 

the norm is usually 5w-30 in the winter time, 10w-30 in the summer. some people will run 0w-30 as well.

 

I always ran 10w-40. Put 43,000 miles in the 2 1/2 years Ive owned it. I just put 15w-40 Rottella T in this last time cuz Ive worked the hell out of it for those miles. It "seems" to run smoother now. Just my $.02.

 

Well, i have done lots of research of this very subject. lol I get a lot of people that ask me what the benefits of running a certain oil are (i'm an AMSOIL dealer btw). People usually only pay attention to the front number in a oil weight designation. lol what they dont realize or understand, is that those numbers, are in regards to weight (or viscosity) with a certain temperature parameter. That being said, the front number is the weight (viscosity) of oil at Winter temperatures. Thats why it says "W" after the number. So lets say you switched from 10w-40 to 15w-40. You havent changed the weight of the oil. Its STILL 40 weight oil. what you HAVE changed however, is the viscosity of the oil at "winter" temperatures (or startup temperatures). Once the engine is warmed up to operating temperature, the front number goes out the window. It doesnt mean anything anymore, because you're still running 40 weight oil, whoes weight(viscosity) is determined at operating temperatures of around 210*.

hope that clears things up a little bit

 

Thanks wjxavier. It does help. Given the beautiful winters we have in Cleveland, along with the usually balmy accompanying temps, I think your advice on 5w-30 in the winter might be the ticket. Will give it a go. I will then switch it as you suggest in the spring for the 2-3 weeks of good weather we have.

Related, is there a better type oil for flat tappet lifter engines? I had heard Lucas makes an oil designated as a racing oil that is supposed to lubricate these older engines better. Do you know what the particular characteristic is that makes it better?