I think those numbers are kinda low. For comparison, my Auber reads

Cold Idle 52
Cold 2K 52
Hot Idle 20
Hot 2K 50+

I think the spec is 10 psi min when idling, and close to 50 at 2K. Light comes on around 5-6 psi.

 

15w40 or 20w50 would be even better.

 

From a pressure standpoint, is 5W40 any different than 10W40 once you get to operating temp?

 

 

Yes.

The numbering system on oil means xx viscosity With the equilient protection when oil is Hot of xx Weight.

So 5W40 means an actual 5 Weight oil (fairly thin) that protects your motor when the oil is hot as if you had a conventional 40 Weight oil in your engine.

A ten Weight oil is double the thickness of a 5 Weight oil, so 10W40 means that you have a 10 Weighted actual oil in your motor, but when it is hot it protects as well as an old conventional 40 weight oil.

In general, all oils get thinner when they are hot. That first number is showing you the actual Weight of the oil when it is "cold."

Well, all oils get physically thinner as they heat up regardless of how much protection they give. 5 Weight hot will be thinner than 10 Weight hot. This impacts your oil pressure!


Decades before blends and synthetic oils, people had to run straight weight conventional crude oil, and that would look like 30W30 today (really thick actual oil when "cold" and only protects like 30 Weight). They'd call that sort of thing "Straight cut" or Straight Weight... and as a racer you'd have to choose if you wanted almost gummy oil when the motor was cold to get the higher protection of thicker oil later after the motor got hot.

Some Ferraris back in the 1950's race circuits would have to start their motors when cold with a 20W20 weight oil and then once the motor warmed up a little they'd drain out that oil while simultaneously adding in 40W40 with the motor running!

 

All true on the oils, but yours is not going to go up to normal with the thick oil. You either have:

1. Slipped cam bearing
2. Broken oil pump
3. Worn cam bearings
4. Worn crank bearings

Given the mileage, unless the previous owner seriously neglected the oil change interval, you are looking most likely at 1 or 2. 1 and 4 can be checked by taking the oil pan off, 2 requires the oil pan to come off as well as the front cover. There was a complete drivetrain for sale in the forums for $750 last week - I recommend you buy.

 

Yes, but both oils are 40 when hot. They only behave like a 5 and 10 when cold. I thought the numbers referred to actual viscosity measurements. The first being how it behaves in when cold, the second when it is 100C. I agree that the 5W will be thinner than 10W on startup, so switching to 10W (or 15W as Dave suggested) may boost his cold pressures a bit. But since they are both 40 when they get up to temp, the viscosity (and oil pressure) should be the same, no?