This seems backwards to me, but lately the truck has been getting a little on the warm side, and the oil pressure goes up a bunch at the same time. I would think the oil pressure would drop, because the viscosity would be lower due to the heat, making the oil less resistant to flow.

Right? What's going on?

 

Check your gauges ground.

I am assuming this is the electric gauges on the dash, right?

If you have mechanical gauges, then I have no clue.......because it goes against everything that I know for oil pressure to go up the hotter the engine coolant is.

 

Yup, the ones in the dash

 

With multi-vis oil, it is the opposite, thicker when hot and thinner when cold. It is hard to get your head around. With single viscosity oil, when it breaks down in heat, it can get thinner. My truck has an iffy conection for the oil sender and it sometimes drops to zero, scares the bajesus out of me...Mark

 

Well actually it isn't quite like that. When multi-vis is heated, it thins, but not as much as it would without the viscosity index improver additive. So oil that has the viscosity of 15 weight at 40 below and has the viscosity of 40 weight at 250 degrees is still thinner at 250 than it is at -40.

The problem is an illusion, probably caused by a poor dash ground.

 

I feel like I have my own personal linbacker keying on me for some reason. That was clear as mud by the way...Mark

 

Gotta love it, don't you Mark !

 

Yeaaaaaaah, love it.......Mark

 

No problem, glad to help. By the way, what's a linbacker?

 

Maybe this can help understand what J is trying to say..

Note Second paragraph

http://www.upmpg.com/tech_articles/motoroil_viscosity/


Basically a Multi viscosity oil flows better at lower temperatures as if it was different grades of a single viscosity oil. All 10w30, 5w30, and SAE30 weights flow the same at 210*F (100*C). The difference is that the multi grade oils would be sludgy or slowed down dramatically, with reference to their ability to flow or move through the engine, when the engine is cold.

What is really cool, which I never knew before reading that article, was how they determine multi viscosity oils. They do the viscosity test at 210*F and then the do the same oil testing at a colder temperature. The flow rating from each test determines what they specify the oil rating is....(IE: 10w30). W... stands for Winter...or the oil testing at the colder temperature, again, something I didn't know...


Thanks for the edumucation fellows and gentiles...

 

It's the guy who paid Jeremy Lin lots of money to throw a rubber coated ball into a basket.

 

Exactly...Mark

 

Tmi, T...Mark

 

Timmy ???

 

How old is your sending unit? They do go bad.