5w-50 | help me choose?

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MRT

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I've decided to try 5w-50 in my 1988 7.3L diesel (non-powerstroke). It's in great shape, but there's some blow-by + oil consumption that a 50 grade mitigates. I've used Amsoil 20w-50 and 5w-40 (and of course 15w-40). With the 5w-40 there is great low temperature starting, and with the 20w-50 blow-by and oil consumption are minimized. Thinking 5w-50 will be a good choice.

Looking for a 5w-50 with SN & CF rating, here's the contenders so far:
Red Line http://www.redlineoil.com/product.aspx?pid=135&pcid=21
Mobil 1 http://www.mobiloil.com/USA-English/MotorOil/Oils/Mobil_1_5W-50.aspx#
Amalie http://www.amalie.com/Passenger-Car-Motor-Oil/Elixir-Full-Synthetic/5W-50

Amalie has the lowest VI (150), so perhaps that indicates less VI improver and less tendency to shear. RL has the highest VI (186) and the highest 100C viscosity (21). M1 and Amalie both have the same 100C viscosity (17.5).

Thoughts?
 
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how much oil does it use? the 6.9 in my sig uses about a qt in 700 miles and the guys on the truck forums say thats about normal for our idi's. mine hated 5w40. it drank it so fast that i started filling it with 15w40. so far supertech and delvac 1300 make it consume the least
 
5w-40 is in there now, and it's about 1600 miles per quart. With 20w-50 is was around 3000 per quart.

I think a lot of the oil burned is from mist entrained in blow-by that goes through the depression regulator into the intake manifold. One can see this by taking off the intake screen below the air filter housing and noticing the oil residue. 50 grade seems to make a better ring seal.
 
You might be able to get Castrol 5w-50 at AZ or AAP when they have Castrol deals.

How cold does it get where you are? The 15w-50 might be all you need anyhow.
 
Originally Posted By: MRT
Amalie has the lowest VI (150), so perhaps that indicates less VI improver and less tendency to shear. RL has the highest VI (186) and the highest 100C viscosity (21). M1 and Amalie both have the same 100C viscosity (17.5).

I wouldn't worry much about shear with Red Line. I would worry about your rate of consumption at the cost of Red Line, though.
wink.gif


I know you didn't ask, but would a 20w-50 or 15w-40 in conventional not be the most cost effective, given your consumption? Don't mind me, I just panic about using synthetic in oil burners.
 
Originally Posted By: Bandito440
You might be able to get Castrol 5w-50 at AZ or AAP when they have Castrol deals.

How cold does it get where you are? The 15w-50 might be all you need anyhow.
Around 5F, block heater not used. 15w is OK, 5w works really well.
 
Originally Posted By: Garak
Originally Posted By: MRT
Amalie has the lowest VI (150), so perhaps that indicates less VI improver and less tendency to shear. RL has the highest VI (186) and the highest 100C viscosity (21). M1 and Amalie both have the same 100C viscosity (17.5).

I wouldn't worry much about shear with Red Line. I would worry about your rate of consumption at the cost of Red Line, though.
wink.gif


I know you didn't ask, but would a 20w-50 or 15w-40 in conventional not be the most cost effective, given your consumption? Don't mind me, I just panic about using synthetic in oil burners.


It's quite a bit better with a 50 grade, around 3000 miles/quart. Not consuming enough to make me worry about oil cost.
 
Well, it's not huge consumption, but in light of longer OCIs one traditionally sees in a diesel over a gasser, it would at least give me pause. If it were me, and I'm loathe to say it, I would probably stick to a 20w-50 conventional if that provided best results. Your climate is pretty good, unless you're regularly driving up Mount Hood in the winter.
wink.gif
 
if a large amount of oil goes through the CDR valve, I would think getting a cyclonic oil seperator would reduce the severity of the problem. BMW uses them in their engines.
 
Originally Posted By: artificialist
if a large amount of oil goes through the CDR valve, I would think getting a cyclonic oil seperator would reduce the severity of the problem. BMW uses them in their engines.


Yes, that's a very good idea. Thought about making some type of oil separator with CDR when I replaced the CDR, but it looked like a big time investment. The lazy way is 50 grade oil instead of 40 -- Better ring seal, less blow-by, less oil mist though the CDR.
 
It's strange that there are not very many 50-weight oils that are formulated for diesels. Don't truckers use Lucas Oil Stabilizer to thicken up their 15w40's once the engines start to use oil at a high rate?

It seems like a waste to me to use 5w50, which is only available as a synthetic, in a vehicle that has an oil consumption problem.

Shell does make a monograde 50-weight if you never plan on starting your truck at lower than 40F.
 
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I'd be more inclined to run a thicker 5w40, such as Rotella T6 (HTHS 4.2ish) or Red Line (HTHS 4.4). Red Line's 5w40 is basically a 50-weight anyway -- if you look at Mobil 1 15w50, you'll see the same HTHS.

With the Red Line, you could always slightly thicken the 5w40 with a quart of their 5w50 or something.

Heck, there's stuff like Castrol Edge Professional TWS 10w60, too. It's API SN, has outstanding cold-start properties, and the HTHS stabilizes to around 4.5 after some early shearing. Supposedly one of the reasons BMW chose it for the M cars was to minimize leaking (when cold) and consumption (when run on the track/autobahn).
 
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