Another persective on thick/thin and oil pumps and pressure

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6,902
Location
Louisiana
For those of you who haven't followed in the aditives forum, I've gone round and round trying to degunk my Saab 9-5 since I bought it used back in November. Besides it's rep for sludging if you don't follow strict OCI's of 5k or so with synth, it is also known to have a weeny weak oil pump that wears quickly from the sludgies rolling thru it. Now, I have no immediate reason to suspect anything, but....for future reference, and I know this has been covered in other fashions, but...when wear of the oil pump itself seems to be a motivating factor....would a thicker oil be best to provide a thicker bearing film and raise pressure or would the fastest flowing 0w be the best? Would it be best at that point to bite the bullet and go to say 0W40? Or bite the bigger bullet and just pay for a new pump....? Like I said, no iminent failures I can tell but I just worry it will be an eventuality.
 
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Vista, CA
If a 0w-40 shears out of grade, which it will, you experiment won't show much. You idea is good, just try a 10w-40 instead. I tried M1 0w-40 in my 850 Volvo Turbo and on a hot day on a long commute between San Diego and Phoenix the oil temp went up and the oil pressure went down enough for the brain to shut down the A/C. A uoa showed the oil, after the trip to be a 'thin' 20w. I'll never use an oil with that much of a spread again.
 
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7,409
Location
Austin, TX
quote:
Originally posted by LarryL: I tried M1 0w-40 in my 850 Volvo Turbo and on a hot day on a long commute between San Diego and Phoenix the oil temp went up and the oil pressure went down enough for the brain to shut down the A/C. A uoa showed the oil, after the trip to be a 'thin' 20w. I'll never use an oil with that much of a spread again.
Are all 850 Volvo Turbos this tough on oil? I wonder how all those Porsche and Mercedes-Benz AMG vehicles survive on their factory fill of this oil?
 
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8,937
Location
SC
quote:
Originally posted by LarryL: A uoa showed the oil, after the trip to be a 'thin' 20w. I'll never use an oil with that much of a spread again.
Sorry, I just don't buy that. A "thin" 20w would be something like 5 cSt. If you got a UOA back saying Mobil 1 0w40 was in the 20 wt range at all you've either got major fuel dilution problems or the lab made an error. Period.
 
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Idaho
I'll stick my neck out for the thin-oil folks to target and say that there really are some applications where thin oil isn't a good choice. Some engines are really tough on oil, such as air-cooled VW's. Even if you put an oil filter on them, they still tend to have wide temperature swings. Your engine may well be another. Are you in Louisiana? I cannot imagine it getting cold enough there to be a problem running Delo 400 15W-40 and short OCI. A loose oil pump will definitely pump better with heavier oil. Probably better to get a new pump though. Joe
 

BrianWC

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6,902
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Yeah, I'm in Louisiana. I HAVE run 15W40 no problem short OCI. I would think thicker = better in this case, but....I also would think fast flow and low startup wear would be needed. We've got plenty of time to discuss this. Nothing's wrong w/ the car yet! [LOL!] And an oil pump kit is only $60.
 
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7,409
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Austin, TX
I don't believe thicker oil is going to help increase the oil flow through your engine. It may help the oil pump a little, but this will be more than offset by the increase in back pressure presented by the engine. Do you have an oil pressure gauge?
 

BrianWC

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Louisiana
Eh, read closely. I don't really have a problem. This is hypothetical. But yeah, I AM going to install a gauge at some point. Increase in backpressure....you mean decrease in flow to the head?
 
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1,203
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Oregon
Humm, I thought most sludge motors die early from clogged oil pump screens, oil galleries and the resulting oil starvation.
 

BrianWC

Thread starter
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6,902
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Louisiana
Well, in my case....I've dropped the pan and cleaned the screen, run solvents, and run 2 courses of arx. Except for the bottom tips of the main bearings, I'm pretty sludge free. The other way sludge can cause oil starvation is by (in saab's case, anyway) wearing the pump out so that the pressure falls off once the oil heats up.
 
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169
Location
Sandy Eggo
quote:
Originally posted by LarryL: I tried M1 0w-40 in my 850 Volvo Turbo and on a hot day on a long commute between San Diego and Phoenix the oil temp went up and the oil pressure went down enough for the brain to shut down the A/C. I'll never use an oil with that much of a spread again.
I'd never use anything thinner than 20W-50 in a turbo-boosted engine. I understand those turbo's run real hot. If I lived in Phoenix, I'd be running SAE-40 in that engine during the summer. I'd experience a slight drop in gas mileage, BUT, I'd get no engine wear since none of the moving metal parts would be able to touch each other. It's not a turbo, and I live in Sandy Eggo, but I run SAE-30 in my Grand Prix in the summer, and 10W-30 or 10W-40 in the winter. Regards, Gary in Sandy Eggo
 
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SC
quote:
Originally posted by Gary in Sandy Eggo: I'd never use anything thinner than 20W-50 in a turbo-boosted engine. I understand those turbo's run real hot. If I lived in Phoenix, I'd be running SAE-40 in that engine during the summer. I'd experience a slight drop in gas mileage, BUT, I'd get no engine wear since none of the moving metal parts would be able to touch each other.
Boy, do you need to spend more time reading on here. [Eek!]
 
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1,203
Location
Oregon
quote:
Originally posted by BrianWC: http://www.andrewsofprinceton.com/shared/nines/007.cfm That's a link to a respected Saab mechanic's take on the oil pump situation. He's done a lot of experiementing. Ignore his fear of ZDDP. Here's a link to his index. I has several articles on saab sludge issues. http://www.andrewsofprinceton.com/shared/9s.cfm
I see what you are saying. I guess from what I'm reading a very good oil pressure gauge would be a good idea if you don't want to put in a new oil pump just yet.
 
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1,550
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North Texas
In my experience with Euro-cars, they seem to go against the common trend of thinner being better. They seem to like things on the thicker side of life. My VW Jetta (gas 4 cyl) would give me low oil pressure warnings with anything thinner than 15w40, so i ran 20w50 dino year-round (In TX it wasn't a problem even in the winter). I also found that using any oil filter other than OEM, WIX, or Denso would also cause some problems. While i would not reccomend 20w50 for your saab, i think a 10w30 synthetic or semi-synthetic would be better than the 0w-xx oils, due to the sheer strength of the 10w30. Volvo's and saab's tend to be hard on oil with their low-pressure turbos, but lots of folks put 100's of thousands of miles on them using 10w30, so i'd stick with that. If you want to go with something thinner on the bottom end, you could try the valvoline synthetic Euro Formula 5w40. If your engine is really that gunked up and you cant get it clean have you looked at other possible culprits such as the PVC, O2 sensors, etc?
 
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1,550
Location
North Texas
quote:
Originally posted by BrianWC: Well, in my case....I've dropped the pan and cleaned the screen, run solvents, and run 2 courses of arx. Except for the bottom tips of the main bearings, I'm pretty sludge free.
I missunderstood, i thought you had an ongoing sludge problem. Since you dont, i wouldn't worry too much regardless of what weight oil you are using, just dont let it go too long between oil changes and you should be fine. Although i still think a quality 10w30 would be good for your saab:) While extended drain intervals may be appropriate in some cars, if i had a turbo i would not let it go past 3 or 4k even with synthetic.
 

BrianWC

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Louisiana
Well, I suppose it is ongoing but it's nowhere near as serious as it was. Except for the sludge coating the extreme bottom end, I'm good. I'm also replaced several other parts which may lead to the condition. And I've done such frequent OCIs that OIL oxidizing is not an issue. But read the nitty gritty of this thread to see what/why I am concerned. As for OCI's. Turbos usually aren't that bad on oil. In earlier and other Saabs, 5k is a walk in the park. This one engine PCV combination was the killer.
 
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7,409
Location
Austin, TX
quote:
Originally posted by BrianWC: Turbos usually aren't that bad on oil. In earlier and other Saabs, 5k is a walk in the park. This one engine PCV combination was the killer.
Yes BrianWC, I read through all those articles by Chuck Andrews and I now see where the problems lie with these engines. Looks like installing an accurate oil gauge is prudent in that you will be able to see if you really have a problem, or, if one starts to develop. Three things I see that are important with these engines is, first, don't let the oil get to the state where sludge starts to form. As you've found out, it's not easy and/or cheap to remove the sludge once formed. You might consider a couple more AutoRX cycles to help insure all your oil passages are cleared the best they can be, short of dismantling the engine. Second, you got to keep a close watch on the PVC system. See if there's any modifications that improve it's performance and reliability. Lastly, you want to use as stout of oil as possible. Mind you, not necessarily the thickest oil, but one with very low NOACK and top-of-the-line anti-oxidant/detergent/dispersant additive package. Something like AMSOIL Series 3000 Synthetic 5W-30 Heavy-Duty Diesel Oil or equivalent.(Or, be prepared to change the oil very frequently.)
 
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8,937
Location
SC
quote:
Originally posted by 427Z06: Lastly, you want to use as stout of oil as possible. Mind you, not necessarily the thickest oil, but one with very low NOACK and top-of-the-line anti-oxidant/detergent/dispersant additive package.
Using LC would be a big help in controlling oxidation.
 
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