Effect of Oil Viscosity on Oil Film Thickness

[NICAT]

Originally Posted By: Shannow


The theory is that the rings "skip" over the thick oil film.


I think it is not the theory. It is just the reworded version of "higher oil consumption at rings with thicker oil"

The theory should explain why it is likely to skips over thicker oil film compared with thinner one.

Quote:
I'm not saying that I'm an advocate of the theory, and I personally have never seen thicker oil make things worse, but it gets trotted out regularly...well if you've been here long enough.


I have read your posts on this site many times before, and never found any post that i could disagree with

 

[Silk]

Originally Posted By: NICAT

- Daewoo Nexia, 4 Stroke GM SOHC, 1.5L, 8 Valve


They were sold as the Pontiac LeMans here, and most were lucky to get to 100,000km. they burned oil that's for sure. An Opel engine...I hate to mention Camira to the Aussies, but it was in them too.

 

[Ducked]

Originally Posted By: Shannow
But there's other Shell papers that show increased oil consumption with thicker oils, and the rings being less able to scrape them off.

Rings are the area where I've come across diametrically contradictory studies


Quite a lot of variables. Ring tension (compression?), well, anyway the outward pressure the rings put on the cylinder wall, the precise shape of the compression and oil control rings and the design of the grooves the rings seat in, compression ratio, rpm, and probably a lot more.

This all might make them a bit less predictable than, say, shell bearings.

 

[FCD]

Originally Posted By: Shannow
But there's other Shell papers that show increased oil consumption with thicker oils, and the rings being less able to scrape them off.

Rings are the area where I've come across diametrically contradictory studies

From the countless accounts of anecdotal evidence i have read on dozens of threads on oil burning on BITOG.
It seems that when worn piston rings are what are causing the oil burning, thicker oil doesn't improve the oil burning and even worsens it.
It seems to me that when it does improve oil burning is when valve stem oil seals are the issue, and that is personally what i have noticed in my own cars i have had, my Capri used to drink 20W-50, but after i changed the valve stem seals it hardly burns any.

 

[Shannow]

I had the 2.0 "big block" in my wagon...(actually, my engineering thesis was to develop an in cylinder visualisation test rig for the various heads available on that engine.

My parents had the Nissan Pulsar "Vector SSS" with the Camira Engine in it...bloody thing went forever. Sister had an auto hatchback same engine, and while the miles were not high, the abuse was.

 

[SR5]

I had the 1.6L JB Camira wagon. It didn't burn much oil, ran it on GTX 20W50 mostly, the cheaper Castrol XL 20W50 when a bit short, and the Castrol 10W60 full synthetic when I put together enough left overs from my motorcycle oil changes. It had the 5 speed manual.

 

[A_Harman]

Originally Posted By: Silk
Originally Posted By: NICAT

- Daewoo Nexia, 4 Stroke GM SOHC, 1.5L, 8 Valve


They were sold as the Pontiac LeMans here, and most were lucky to get to 100,000km. they burned oil that's for sure.


So maybe the thick oil really helped...

 

[NICAT]

Originally Posted By: A_Harman
Originally Posted By: Silk
Originally Posted By: NICAT

- Daewoo Nexia, 4 Stroke GM SOHC, 1.5L, 8 Valve


They were sold as the Pontiac LeMans here, and most were lucky to get to 100,000km. they burned oil that's for sure.


So maybe the thick oil really helped...


May be not.
I contacted friend (who is the previous owner of the engine) about engine service history.
Piston rings and valve guides has been replaced before.
But not camshaft, crankshaft or any other things. Used 15w40 (or 10w40) oil in winter, and 20w50 in summer.
The car was used as a taxi in highway, From one city to another. May be 70% of the time in 5th gear.
May be, less Cold Starts or less engine revolutions per KM helped rather than thicker oil

Those models are generally used as a taxi. And i have never heard about their oil consumption problem.


I have BMW E60 with M54 engine, it is consuming 1Ltr per 1500KM, and its 230k KM.

 

[benjy]

girlfriends new 13 malibu 2.5 L DI engine was using the factory fill dexos I oil, dumped at 1,000 miles put in brand name 5w-20 dexos I semi-syn, still using a qt on a thousand so looking for its 3rd qt i dumped it a put in brand name 10-30 synthetic likely group III, end of oil usage pretty much!! oil changed yearly 10,000 miles + or - only add here + there less than a qt in that period. very conservative driver with 50.xxx miles so far, no DI carbon issues YET!!

 

[PimTac]

Originally Posted By: benjy
girlfriends new 13 malibu 2.5 L DI engine was using the factory fill dexos I oil, dumped at 1,000 miles put in brand name 5w-20 dexos I semi-syn, still using a qt on a thousand so looking for its 3rd qt i dumped it a put in brand name 10-30 synthetic likely group III, end of oil usage pretty much!! oil changed yearly 10,000 miles + or - only add here + there less than a qt in that period. very conservative driver with 50.xxx miles so far, no DI carbon issues YET!!




It’s likely that GovMo engine was breaking in, thus the oil consumption. The 10w30 had nothing to do with it

 

[ZeeOSix]

When the LS6 first came out in the 2001 Corvette there were a lot of reports of excessive oil burning. GM concluded the piston ring tension was too low (they made it lower to get more HP) and the rings would "flutter" at higher RPM, so in 2002 they changed to rings that had more tension which cured the problem.

My 2000 Hayabusa seems to use way more oil when I use Mobil 1 full synthetic motorcycle oil. If I use a conventional oil like Valvoline motorcycle oil (both were 10W-40) there's no noticeable oil usage. This is the only time I've experience a huge change in oil usage dependent on what oil I've used. I use Mobil 1 5W-30 in my Tacoma V6 and it doesn't use any oil over a 5000 mile oil change.

So oil burning can be a whole variation of factors from mechanical design of the ring pack to what oil is used.

 

[Silk]

We were warned to never attempt to rering a Camira (and other Opel engines the same), it wouldn't be successful. Perhaps they were the first of the low tension ring engines. So we just let them spew oil everywhere. I had a MkII Escort once, I put some nice synthetic 5W-30 in it...it was gone in a week, so then ran it on 25W/70 until I reringed it....the bearings were perfect and went back in.

 

[FCD]

Originally Posted By: Silk
We were warned to never attempt to rering a Camira (and other Opel engines the same), it wouldn't be successful. Perhaps they were the first of the low tension ring engines. So we just let them spew oil everywhere. I had a MkII Escort once, I put some nice synthetic 5W-30 in it...it was gone in a week, so then ran it on 25W/70 until I reringed it....the bearings were perfect and went back in.

Yeah, i would not put 5W-30 in any old Ford Pinto, Kent, Cologne, Essex engine, 15W-40 HDEO or a good 20W-50 like Valvoline VR1 is what they like best from personal experience.

 

[Silk]

20 years ago, I was just sucked in by all that synthetic hype. Didn't matter what oil, it dissapeared. Typical of many cars babied by an elderly owner...their last new car before retirement, we used to have to run their cars on hot plugs and thick oil, they couldn't afford a ring job.

 

[juggernaut]

Great to hear some of you owned small Fords.

My experiences:

I've owned a 1976 Mk II Escort with 1.6 Kent motor and later a 1979 RS2000 with a 2.0 Pinto motor. I ran Castrol GTX 20/50 in them because that's what we ran in our cars in Australia at the time

I then did a resto mod on the RS2000, modded and built the motor myself (based on David Vizards books on the Pinto motor) and then ran Mobil 1 15W/50 after mineral oil to run it in. None of the motors used oil.

My hobbies have now switch from cars to boats. I run a pair of Merc 8.1's in a boat with 600+ hours. With Merc 25/40 mineral they started using oil around 20 - 30 hour mark. I then ran Merc 25/40 semi synth and they again started using oil around the 20-30 hour mark. Mind you the oil consumption was not excessive and was within the oil consumption range spec'd in the manual. There was never any evidence of oil smoke at start up (hot or cold) or at cruising.

For something different, last July I switched to Penrite racing 15/50 poa/ester with no FM's and initially they used a little oil and have then have not used a drop since. I've heard of similar results with Mobil 1 15W/50 in these motors too.

 

[Shannow]

That Vizard book on the Pinto is great.

THat one at the end where he uses a spark retard rev-limiter on a high boost turbo, with a limit switch on the clutch so he can floor it, full boost, then return to full advance as soon as he lets the clutch out was simple genius...

 

[Silk]

I used a Dual Curve CNG ignition on my 1600 Kent engine with stupid cams, to get more advance at lower revs and still keep 38 deg max. It didn't use oil, and probably used 15W-40 at the time.