Great article on the thick vs. thin debate

[beechcraftted]

For all you BITOG'ers who like to see more info on this suject,
check out the Nov. 09 issue of Hot Rod magazine. Performed dyno pulls on a 372 CID Dart small block Chev using 5 different oils. 30W dino and 20W-50, 5W-20, 0W-20 (race oil), and 0W-10 (race oil). All Lucas oils. HP average was from 3,100 to 6,500 RPM.

viscosity peak HP avg. HP PSI GPM peak temp(F)

30W 475 383.9 67.1 6.1 162
20W-50 477 387.0 67.4 6.5 163
5W-20 479 386.3 59.4 7.2 166
0w-20 (race oil)478 387.5 59.7 7.4 166
0W-10 (race oil)480 387.4 55.7 7.4 165

Lucas reps stated that race oil was designed for 8,000 RPM plus and would show no advantage until then. I was surprised that the 20W-50 was only 1 HP shy of the 0W-20. Also note that the 30W has the lowest oil temp. The testers felt that a syn 5W-20 would be the best compromise for a HP street engine. It was their opinion that high flow at a lower PSI was best.

Interesting

 

[c3po]

I believe Chevy High Performance or Car Craft did this same type of thing a couple of years ago, when I get home I will see about pulling up the article.

 

[Quattro Pete]

Interesting in a way that it shows that these different weight oils don't affect performance almost at all.

Granted that wear was not really their concern here, but for a normal street-driven vehicle, it'd be more interesting if they did somehow relate these findings to engine wear.

 

[Jim 5]

Originally Posted By: beechcraftted
It was their opinion that high flow at a lower PSI was best.

Interesting


Interestingly, in around 2007 GM Duramax engines went from a high pressure oil pump to a low pressure high flow oil pump. There might be something to this.

 

[JohnBrowning]

Well GM has almost always gone with High Flow at lower pressure levels as compared to most of the auto industry outside of Detroit. It all depends on how you design the bearing and journals. If you want to use a higher flow at lower pressure you normally have to make the bearing and journal wider then you do if you go with pressure over volume. You also have to look at more then just the bearings,journals and rod ends!!! FOr instance a lot of Imports still do not use rollerrized top end and many use a common shaft to mount the rockers or the cam followers. This requires more pressure then a rollerrized set up to make sure that the oil supply is always their fast and with enough volume.

The main reason for reducing oil pressure is to reduce drag on the engine to increase fuel economy!In the big grand scheme of things the type of oil pump used makes a bigger difference then anything else in how much drag is presented at the crank. A gerotor design is much more efficient then the typical old style oil pumps used by GM and many other domestics for so long. You can have pressure and volume at any point you want to it really is not a must that pressure be dropped to increase volume and vice versa that is a design element and not much more you can have both if you desire!

For instance GM's small blocks used low pressure systems as did their 60° V6's but the Buick 3.8L used a high pressure oil system.It really is all about what design goals you have and your preference more then anything else. Their is no good or bad only what works. For the longest time Toyota,BMW and Daimler all used high pressure systems. I do not know that they are all doing so today only that it was their preference in the past. Most engines that have had iron clad durability to the point of being legends like the Slant 6, 22RE, Volvo Red Block's, Buick 3.8LV6 etc....all used high pressure systems you almost never run into legendary long life engines using low pressure high volume systems. The reason is that as these low pressure high volume systems age they quickly get to a point where they have neither the volume or pressure to properly protect the engine any longer and few people can do their own work so they just drive them until they drop and then get another one. GM small blocks where notorious for low oil pressure under warranty. It was costing GM so much money they changed the standard and lowered it all the way down to something idiotic like 7-9psi for warranty oil pump replacment.Never mind that when new the oil pressure guage read 54psi or better and now at 34,000 miles latter it is reading at 7psi and the lifters are ticking!!!LOL If the problem will not go away just lower the standard. Kind of like what they did with the North Star's and all the latter engine designs that either used oil like a pig or had rod knock....Just change the standards like the 60°V6's GM had the nerve to say that Rod knock did not represent any durability issues......When the North Star's came out and they where drinking oil like mad GM kept upping the amount of oil usage that was acceptable until they finally found a level that brought their warranty levels down!LOL

So just because GM has decided to do something does not make it a good thing normally when they start changing things it is usually to save money and comes back and bites them in the rear with recalls!Keep in mind that GM did not design the Duramax either Isuzu designed it for it them!

 

[friendly_jacek]

Originally Posted By: Quattro Pete
Interesting in a way that it shows that these different weight oils don't affect performance almost at all.

Granted that wear was not really their concern here, but for a normal street-driven vehicle, it'd be more interesting if they did somehow relate these findings to engine wear.


There was a study done a few years ago when various viscosities of oil were compared on a dyno and wear was measured by weighing magnetic debris collected in oil filters. The thinnest oil used in that study was GC 0W30. 0W30 gave the highest HP and highest wear. I cannot find a link to that study anymore. It was widely discussed here on BITOG.

 

[JohnBrowning]

If lead is low especially lower then iron then 9 out of 10 times your viscosity is fine! As far as HP goes I do not pick my oils based on HP output if I want more HP I can add NOS,,Forced induction or run a higher compression ratio and bigger cam etc....I select my oils based on the idea of my current car getting 500,000 miles or more with out the engine internal ever having to be touched!

I also do not select my oils based on the minute amount of fuel I might save in a years time because the way I drive it would not add up to enough to buy me a cup of coffee at Star Bucks! I want to save fuel I will buy a vehicle that get's inherently better fuel economy not try to get .00000009MPG increase by switching from 5W30 to 0W20. Especially not in an application not calling for a 20Wt.

My oil only has to do a few things well for me to be happy. It has to keep my already clean engine clean and free from excessive deposits. It has to keep wear to a minimum!It has to resist oxidation. If it does all of those things well and is locally available at a decent price point I am completely happy!

 

[Steve S]

J.B. your love of G.M. overall is similar to mine!!!

 

[mechanicx]

I think the oil temperatures of 160 are too slow and might have skewed the results in the real world. I never heard of anyone running their oil below about 180. I think it should be at least in the 212-220 region.

I don't know if I see the need for a high volume pump that's just going to heat up the oil bypassing it. My understanding is that all oil pumps are oversized since the pump has to be more volume due to not being able to create as much pressure at low RPM.

 

[m37charlie]

On my Unimog the thermostat is 78 C. = 172 F. and that's exactly what the oil pan measures at after a long run. I must have a high flow low pressure setup because the highest pressure ever gets on a cold morning is 73 psi = 5.0 bar (I think that's the pressure relief), and at running temp 43-50 psi at 18-2200 rpm. With 5W40 synthetic.

Charlie

 

[MolaKule]

Quote:
Lucas reps stated that race oil was designed for 8,000 RPM plus and would show no advantage until then. I was surprised that the 20W-50 was only 1 HP shy of the 0W-20. Also note that the 30W has the lowest oil temp.


I never heard of race oil being designed for a certain rpm. Sounds fishy.

The deltas (differences in values) do not represent a statistically significant set of numbers. I don't see that they proved or disproved anything.

 

[Steve S]

Originally Posted By: MolaKule
Quote:
Lucas reps stated that race oil was designed for 8,000 RPM plus and would show no advantage until then. I was surprised that the 20W-50 was only 1 HP shy of the 0W-20. Also note that the 30W has the lowest oil temp.


I never heard of race oil being designed for a certain rpm. Sounds fishy.

Lucas oil must have perfected the RPM thing.

 

[mechtech2]

If thinner oils do not produce more power, then why do Nascar cars use extremely light oil for qualifying?

Also, an engine's rings can be designed for efficiency at different loads, and with different oils.

 

[Steve S]

Thet do not produce any power . The thin oils create less of a loss of power.

 

[mechtech2]

Yes, I know that.
Excuse a poorly worded post!

 

[SlowGT]

Originally Posted By: JohnBrowning
I also do not select my oils based on the minute amount of fuel I might save in a years time because the way I drive it would not add up to enough to buy me a cup of coffee at Star Bucks! I want to save fuel I will buy a vehicle that get's inherently better fuel economy not try to get .00000009MPG increase by switching from 5W30 to 0W20. Especially not in an application not calling for a 20Wt.

My oil only has to do a few things well for me to be happy. It has to keep my already clean engine clean and free from excessive deposits. It has to keep wear to a minimum!It has to resist oxidation. If it does all of those things well and is locally available at a decent price point I am completely happy!


that's where i am too. if i wanted fuel economy i'd drive a 30+mpg civic instead of my 11mpg 8.1L SUV.