Thin Oil Theory Test

[Tommy]

Zero as in no change in consumption or pressure or are you giving the idea a zero mark?

 

[SPITMAN]

Why mess with a good thing, the 15W-40 seems to give you excellent service with very little consumption. Unless you really feel the need to experiment, don't change from your selection. In the event you do want to try the XW-20, go with the cheapest as you may be dumping it at a shorter than usual OCI if it doesn't perform to your standards.

 

[Gary Allan]

I'll say that your pressures will be lower ..most certainly at idle (warm-more so).

Your consumption will increase, IMHO.

Since I doubt you will continue to use this oil beyond determining that it isn't for you, I'd recommend the MC 5w-20 @ $1.50-$1.75/quart.

You will sap less hp due to oil viscosity at all times. This may or may not result in increased fuel economy.

 

[AEHaas]

Going from a 40 wt to a 20 wt may be too big a jump. Try a 0W-30 first. I would try Mobil 1. That car has a lot of miles and may NOW require a thicker oil. If the car NEEDED a 40 wt oil for the first 450,000 km then it may actually need a 50 wt oil now.

Certainly it is worth experimenting. Put the 0W-20 Mobil 1 in there and send me the operating pressures at 2,000, 3,000 and 4,000 RPM at full (normal) operating temperature. First collect the same data with the old oil under the same conditions for each oil. Get a UOA at 1,000 miles. If the 20 wt oil flunks I will buy you the next oil to try, the 0W-30 Mobil 1.

[email protected]

[ February 12, 2005, 03:54 PM: Message edited by: AEHaas ]

 

[pscholte]

quote:

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Originally posted by AEHaas:
Going from a 40 wt to a 20 wt may be too big a jump. Try a 0W-30 first. I would try Mobil 1. That car has a lot of miles and may NOW require a thicker oil. If the car NEEDED a 40 wt oil for the first 450,000 km then it may actually need a 50 wt oil now.

Certainly it is worth experimenting. Put the 0W-20 Mobil 1 in there and send me the operating pressures at 2,000, 3,000 and 4,000 RPM at full (normal) operating temperature. First collect the same data with the old oil under the same conditions for each oil. If the 20 wt oil flunks I will buy you the next oil to try, the 0W-30 Mobil 1.

[email protected]

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Based on your premise, I would recommend GC as it is a thicker 30 wt. While avaiability is an issue with GC, it appears that at Autozone at least, Mobil 0W-30 is going to become just as scarce as the Elixer of Tibological Triumph.

 

[Tommy]

I just read the writings of AEHAAS.....maybe there is something to this? I thought I would do my own little test (just for kicks) with my older car, a 1988 Volvo 740 non-turbo with 470,000 KM on the odometer. Oil consumption is now 1 qt. per 5000 KM using Amsoil AME 15W40, oil pressure is good. (I do have a guage installed)

I would be very interested in hearing your thoughts on what oil I should try:

Motorcraft 5W20
Mobil 1 0W20
Amsoil 5W20

Please also state your predictions on possible oil consumption & oil pressure changes.

Thanks!

 

[Spitty]

Zero.

 

[Tommy]

You guys are probably right.......sometimes it is good to push the envelope however.

I was just looking back at my old analysis reports for this vehicle - back at 362,000 KM, I had a fuel dilution problem, (defective MAF) the oil had thinned to 20W with Amsoil AMO 10W40...here is how the numbers came in at 12,000 KM. There was no increase in oil consumption. It is interesting to note that these were the lowest wear numbers I had ever acheived with this engine!

Analysis by Metrotech Calgary, elements not listed were 0. I am running an Amsoil bypass filter.

code:

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Lead 1 Calcium 2000+

Copper 2 Zinc 911

Silcon 38 Phosphorous 806

Iron 9 Manganese 88

Aluminum 1 Magnesium 34







Viscosity (100C) 8.725

Solids (% V/V) 0.1

Fuel Dilution YES

Glycol NO

Water (% V/V) 0

Base Number 8.80

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[ February 13, 2005, 11:11 AM: Message edited by: Tommy ]

 

[noob]

1qt per 5000KMs using Amsoil 15w40 is kind of high. Is it leaking or burning?

 

[Gary Allan]

quote:

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You guys are probably right.......sometimes it is good to push the envelope however.

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Well, it saves you all the intermediate terrain if the stuff is functional for you. You will either learn that it does work or it doesn't. It's no more or no less valid a manner of figuring out the right grade. I would highly doubt that your engine is going to spontaniously self destruct. Since you're using UOA ..you're not doing this blind.

I will predict (let's have a pool here

) that, if your usage is mostly highway or of long event duration, consumption will go up. If this is a short trip driver ..that consumption will probably remain the same. This is under the condition that you've locked down your fuel dilution problem. A 40 weight thinning down to a 20 weight is one thing ..a 20 weight has very little room to thin. I say fuel economy for the long haul scene will be unchanged ..and for the short spin usage it will probably increase ..but it may not be all that much.

What's everyone's "pick"??

 

[buster]

I think 30wt oils are ideal for most cars, even those that callf or 20wt oils. In many European sedans or cars that see speeds in excess of 100mph on a daily basis, I'd go with a 40wt oil. You have to let oil analysis be the guide and then you go from their. For my new car, I'm going to run most likely Mobil 1 5w-20 in the winter, M1 10w-30 EP in the summer. I'm also thinking of running M1R all year round.

I also think it's stupid to just use thick or thin without doing an analysis. As I've said before, if your getting great wear with a thin oil, stick with it and enjoy the MPG benefits and HP gains. As the car ages, then bump up to a heavier oil. It's really a non-issue at this point I think.

 

[Tommy]

I changed out my oil yesterday with Motorcraft 5W20, along with new full-flow and bypass filters.

Oil pressure (hot oil) is unchanged at all engine speeds except at idle and 1000 RPM, where it showed 6-8 PSI. lower.

1dle 22 PSI
1000 25
2000 50
3000 52
4000 60
4500 60
5000 62

I am happy with this....now on to phase II. How will it be for oil consumption? I drive 200 KM per day in mountainous terrain - my first analysis will be in two weeks! (if consumption is not an issue)

[ February 13, 2005, 06:09 PM: Message edited by: Tommy ]

 

[Gary Allan]

Well, with that kinda mileage you should find out quite soon. You'll definitely find out what duration this stuff will last in your application in a very short amount of time.

You seemed to report almost linear consumption with the 15w-40. I wonder if this oil will follow the same pattern with perhaps more frequency or accellerate in consumption over the OCI.

Some have reported some rapid consumption when switching oil chemistries ..that settles out further into the OCI.

 

[AEHaas]

Shell Global Solutions: Deposit Formation and Control in Engine Lubrication - Mechanisms & Models, Ian Taylor et al. Automotive Lubricants Group. Shell Global Solutions (UK).

This articles show that the piston-ring seal is best with thinner oils. The oil film thickness is actually greater. It is therefore possible that the oil consumption will go down using thinner oil.

aehaas

 

[Tommy]

Noob,

This engine does not leak. I would not consider this consumption rate excessive for a high-miler.

quote:

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This articles show that the piston-ring seal is best with thinner oils. The oil film thickness is actually greater.

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AEHaas,

This is hard to wrap ones mind around....thinner oil, thicker oil film?

 

[Shannow]

It's not quite how I interpreted the article. The ring spent less time "cocked" and thus had a more concentric arrangement with the bore...better ring seal.

 

[Ray H]

10W-30 Chevron Supreme rules!

 

[Jimbo]

Except for opposed engines (Subaru, Porsche) little, if any oil consumption comes from the piston ring area. Most of it is due to worn valve stem seals, especially in modern OHC designs that put lots of oil up there. The ring seal theory described relates to compression, not oil control rings anyway.