If you are still losing pressure, even with a new pump..... yeah. Gotta do something about the bearing clearances. As a bandaid fix, you could go to a thicker oil.... 20w50 or some such. Not sure how much that would help.... High volume/pressure pump might make up for it as well.

 

It's not so much the 5W vs 10W as it is the xxW-30, and conventional oil. The "big number" tells you (very generally) what kind of base oil you've got. Since a xx-30 grade is the "easiest" oil to make (fewest viscosity additives, etc) it's by far the most consistent from one brand/grade to the next, but they still vary a bit.

API grades are "mandatory"; ie you can't derate or over-rate an oil for viscosity. If it tests to 30 it's gotta be labeled 30, but the actual test numbers are what counts ... one 30 wt might fall in the 26-ish range while another might fall in the 34-ish range, and others in between. They would be tested at both room temperature and at 212F and would have to meet "big number" grade at both. They would all meet spec for 30 wt rating, straight or muligrade.

It's entirely possible that one brand/grade 5W-30 is actually slightly higher viscosity at temp than another's 10W-30, but they would still be close.

If you switch to a different "big number" grade, or change brands, yes, they could react differently to temperature changes. I would not suggest your experience isn't valid or real; I would even say it's expected.

You do need to be careful to not confuse pour point or appearance out of the bottle with what is actually going on in the motor under pressure and temperature. API tests for viscosity and pour point are different and not necessarily related, at least to the extent you can conclude one indicates the other with any consistency.

There is even some evidence that at least some North American oils don't all deal with elevated temperatures well; the API has so far refused to require a High Temperature High Shear rating (HTHS, done at 302F) so API oils are only rated at 212F; Europe and Japan have required this for a decade and some European OEMs have used it for two decades to recommend oils for their cars.

API is, it's worth noting, a group of oil companies and auto manufacturers. By all accounts it's the oil companies who've resisted the adoption of a HTHS test so far; the OEMs want it and have reacted to API's foot-dragging by creating their own specs that incorporate it (eg Dexos, etc). API does have an approved standard HTHS test regimen, it's just not required to get a grade and a donut.

You would think there was a reason. The oil companies give some mumbo-jumbo about "confusing consumers". I don't know how that could be genuine when the whole ZDDP issue is nothing if not confusing to consumers.

My earlier post should be seen in the context of him switching specifically from 10W-30 to 5W-30 and low oil pressure only. Maybe I should add that I assumed he used a similar quality oil in both cases, in which case differences, if any, would be slight. The 10W might result in higher oil pressure at startup by a few PSI if outside air is cool or cold but once the temp gauge is moving at all they should be essentially the same viscosity, so in that light he still needs to fix something. I think we've all used, say, 20W-50 oil in worn engines to get pressure up on a tired engine, but zero is zero. I don't think that's high enough to just switch oils and go, but even 5 PSI is way better than 0.

 

Well, it's not the only *possible* reason for your problems ... there could be a chunk of silicone in an oil passage, for example, and somehow your new oil filter might be plugged, it could be cam end play or bearings, but checking main bearings is the next logical step.

 

did you use a fram filter ... many fram line of filters are garbage... (I doubt its your issues just the same though)

 

It's a real shame but I wont be able to work on it much further to do working on the road for a few weeks...
I will pop her open again when I get a chance, thanks again for all the help

 

Alright, should I just order main bearing and rod bearings before I pop the pan off again?

Would you choose to do a full rebuild or just get by with the replacing the bearings?

 

Depends on the budget..... If you can afford a full rebuild, it sure wouldn't hurt at 160K plus miles....

If you just wanna get by for a while, I would use some plastigage on the rods/mains, and decide from there which ones, or all... to replace.

If you can afford the rebuild, but, are on the fence about it.... do a compression/leakdown test, and see what kind of shape your cylinders are in. If they are marginal, or worse... go for the rebuild. If the numbers look good, just go after the bearings.

 

Thanks again for the help HeyYou,

What can a guy expect for the cost of the rebuild? How many hours for a certified mechanic?

 

A lot.... you can actually buy reman motors for less than what it would cost you to pay someone else to do it for you...... If you were going to do it yourself, THAT is where the savings would come in.