Checking here and there for ideas.

[MAKG]

thats what I just said

Except your statements about what 30W does at operating temp are not specified by the SAE spec. It could be just anything up there. The spec is at 0 deg C.

 

[Tedybear]

Wow, no one here seems to understand multigrades.

The 10W or 0W or whatever tells you the viscosity at 0 deg C.

The other number (30 or 40 were mentioned) tells you the viscosity at 100 deg C.

This means 0W-30 is THE SAME at operating temperature (pretty dang close to 100 deg C) as 10W-30. 10W-40 is not.

The "W" is for cold starts with no block heater. Period.

So, no, you aren't going to tear the heck out of your engine by using 0W-30 unless you do something mind-numbingly stupid and remove the thermostat. While 10W-30 is fine for cold starts on these vehicles all the way down to 0 deg F, 0W-30 ought to work fine in the winter almost anywhere north of Jacksonville.

I do understand the concept and theory behind multigrade oils. Problem seems to be that people fail to understand a 20 year old engine was never designed to use an oil as thin as a '0' weight. At best, with an engine in decent shape? Looking at 5w30 as a rule. 0w30? You'll have volume, but it might not have enough oil thickness to create the resistance needed to build pressure upon startups. That's why the designers 'created' the 5w oil. They needed it thin enough for cold starts, but thick enough to be able to get the pressure.

With current modern engines? The passageways are even smaller, and the bearing clearances are that much tighter. So ideally a '0' weight oil works well to get volume and pressure.

Main reason I went with 10w40 was to ensure the system was able to function well at above the zero mark, and the Lucas is used to aid in preventing dry starts. Lucas needs to do it's job for maybe 2 seconds after the engine starts--The oil system will pressurize that quickly. Plus I wanted the protection of the 40w when running at normal temp, due to the engine already being high-mileage. We do get some sub-zero temps in my area, it doesn't happen that often...But normally on even the coldest winter day? It's usually single digits. (anything colder then 10? I'll just take the Sprinter in--it's got better heat LOL)

I'm not sure why this is so hard to understand, or the snide comments about watching the engine blow up--Back when this truck was made? We didn't have synth oil...We just where only a few years into 5w30 grades...and 0w30 wasn't used. Do I personally think running 10w40 will harm an engine that has over 125,000 miles on it? Maybe if I lived near Watertown, NY...where the temps are known to go to below zero during the wintertime..and decided to jack-rabbit out of the parking lot after just starting the engine.

S-

 

[Tedybear]

As a sidebar note:

Explain to me the following. Why is it that an oil system can generate 50lbs of oil pressure at idle when stone cold...considering the weight of the oil is 10w. However a "hot" or fully warmed up engine can only manage about 20lbs of oil pressure when the 'multigrade' oil is supposed to be as thick as a 30 or 40w? At the same idle speed of course.

S-