Forget Mileage, Which Maximizes Engine Life?

[aquariuscsm]

Good points Caterham. Using the oil viscosity according to how the car is going to be driven is the best advice so far in this thread. That`s what the fsm`s have said for my 3000GT and 300ZX. Use 10W30 for gas mileage/everyday driving and 10W40-20W50 for racing and extended high speed driving.

For example,I know a guy with a TT 300ZX who uses 20W50 pyb and races his car on a regular basis. He has over 300k on original engine and turbos,no oil usage,and all 6 cylinders still have factory spec compression. My other friend who has a TT 300ZX has already blown 2 engines racing,and he`s always used 10W30 dino. He`s the prime candidate for a thicker oil. Me,on the other hand,I never race or track,so 10W30/40 is the ideal oil for me.

 

[JOD]

Originally Posted By: CATERHAM
The mistake in your logic is that while fuel economy may be the motivation in the move to lighter oils, that doesn't automatically translate into increased wear.



While well-intentioned, you're wasting your breath. The false dichotomy just isn't gonna die: better fuel economy=reduced protection...

I chalk it up to the fact and anything with "conservation" and "government" in the title skews some people's abilities to look at things objectively.

For the record, fuel economy is of no concern to me with respect to lubricant choice, and neither is "what they use in Australia". I'm glad to have the options that I do (I don't live in Australia), and I'm using the thinnest $3.60/qt lube I could find (Honda/Idemitsu 0W20).

 

[CATERHAM]

JOD I know you're right.

It reminds me of a quote from Einstein when questioned by someone about something alone the lines that "that's just not common sense". To which Einstein's response was:

" Common sense is the collection of prejudices acquired by age eighteen."

 

[OVERKILL]

Originally Posted By: SteveSRT8
^^excellent point. Oils have gotten awfully good in the last few years.

Another example of crazy specs is Chrysler. Their Hemi specs run from 20w in the passenger car and light truck 5.7's to 30W in the heavier duty trucks to 40w in the SRT models.

Nearly identical engines with differing duty cycles.


A lot like Ford and their 5w20/5w50 Modular thing between super Hi-Po and non apps.

 

[hooligan24]

Originally Posted By: CATERHAM
But that does make sense. How an engine is used is the single biggest factor in how thick an oil you need to run in it.

So what's the solution? If you drive conservatively run the lightest oil recommended for the engine family even if it's the SRT model as in the case of Chrysler. If you use a lot of WOT with a hot engine use the 30wt oil. If you take the car to the track run the 0W-40.
These are only approximations and I don't want to sound like a broken record but the ideal solution is to install an oil pressure gauge and learn how to use it. Why? Because it's your own onboard viscometer that tells you how thick your oil is every second the engine is running. This way it becomes impossible to deliberately run an oil that is too light for the way you personally drive. That's right I said impossible. So you can run your favourite light 0W-20 oil (in your SRT) and you'll know the conditions under which the oil may get too thin and you simply take it easy or run a slightly heavier oil.

The thing is most people are not into motor oil, don't want to think about motor oil and have no intention of paying any attention to an OP gauge. They simply want to be told what oil is safe to run in their vehicle so they don't have to think about it no matter how they drive. That's why you can get a wide range of recommended oil grades from a manufacturer for the same engine in different applications, countries, climates etc. They are trying to predict how the vehicle will typically be used which is no easy task.


How do you know for sure you are running the lightest you can if the factory service manual says normal oil pressure is between 4-82 psi? I have my oil pressure sender in the head. Oils between 2.9 and 3.5 HT/HS give a hot(195f) idle of between 18-25psi and 35-40psi at 3-6k rpms, depending on the ht/hs. The OEM head gasket has an oil flow restrictor integrated into it, which I assume is to keep from flooding the head in the upper rpms. The weird thing is, if I throw in some Redline 10w40 and hit the roadcourse, i still dont see over 40psi during redline runs. That has had me thinking in the past that maybe the bottom end is seeing high enough oil pressures to cause the pump to relief pressure, but since the head gasket restricts flow, I can only see so much pressure at the head.

edit: cold idle pressure is 75psi+, and at 2k rpms, pressure goes up to 95psi on my gauge

I guess the only way to find out is for me to install an oil pressure sendor between the pump and the filter mount. From what I have read online, the oem oil pump is a high flow model used on Dodge V8's

 

[TFB1]

Most oil pump relief/bypass are in the 80-90psi range and yours apparently agrees... While there has apparently been scare tactics to to make people believe their pumps are running in bypass, I'd say it's a RARE occurrence in a engine at normal operating temp, even when running 40 or 50W oils...

Only 40 psi at six grand would scare me, hopefully you have more pressure than that in the lower end...

 

[friendly_jacek]

I totally agree with 90% things said in this discussion, but cannot agree with with a blanket statement/myth that lower viscosity oil itself prevents a startup wear.

Study after study shows that startup wear is mostly corrosive.

Here is one dated as early as 1960's and nothing changed since:

Quote:
Studies in laboratory engines equipped with radioactive piston rings show that wear is highest during a cold startup. Corrosion by condensed combustion products is responsible.


http://papers.sae.org/600190

Mind you I'm not saying lower vicosity oils are bad, as they are great for easy starts at low temps and increased fuel efficiency. I use 0W20 oil myself in my Prius.

If one has ANY proof that lower viscosity oils decrease wear please feel free to post. Common sense is not enough as it isn't a scientific method.

BTW, if one really wants to decrease a startup wear, there are legitimate ways: milder climate, garage, block heaters.

 

[CATERHAM]

Originally Posted By: friendly_jacek
[/quote]
BTW, if one really wants to decrease a startup wear, there are legitimate ways: milder climate, garage, block heaters.

This is a contradictory statement to your premise that lower viscosity oils don't reduce start-up wear.
These three "legitimate" method lowers the viscosity of oil on start-up but running a very high VI oil and an oil no heavier than necessary at operating is no less legit.

 

[friendly_jacek]

Originally Posted By: CATERHAM

This is a contradictory statement to your premise that lower viscosity oils don't reduce start-up wear.
These three "legitimate" method lowers the viscosity of oil on start-up but running a very high VI oil and an oil no heavier than necessary at operating is no less legit.


No, there is no contradiction, the higher the engine temp is at the start, the lower the wear due to less acid condensations and less cylinder wash with fuel.

The higher temp will increase oil viscosity at start, but oil viscosity itself has no impact on start up wear.

As a matter of fact, many years ago a BITOGer referenced a study (I wish I could find it now) done in mining industry in Alaska and trucks using low vicosity oil had more engine failures than regular HDEO.

The difference was explained by some that low vicosity oils enabled starts at a much lower temp that was harmful to engines and higher viscosity required engine prewarming that was beneficial to engines.

 

[friendly_jacek]

I couldn't find the study I mentioned above, but found this that could be related:

Quote:
Based on used oil analysis from the 1999 Cummins N-14 field tests, a leading commercial synthetic SAE 5w40 had statistically higher wear than a leading SAE 15w40 using A.P.I. Group II base stock plus a premium additive system. Both had the same A.P.I. CH-4-SJ/CES 20076/Mack EO-M Plus quality level.

The synthetic is a mix of 74.6% PAO, 0.4% Ester, and 25% Alkylated Naphthalene.


https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=531922&page=1

 

[OldCowboy]

Originally Posted By: friendly_jacek

Study after study shows that startup wear is mostly corrosive.

Here is one dated as early as 1960's and nothing changed since:

Quote:
Studies in laboratory engines equipped with radioactive piston rings show that wear is highest during a cold startup. Corrosion by condensed combustion products is responsible.


http://papers.sae.org/600190



Not trying to start a fight, but in 1960, the highest API grade available was SB and many people were still using non-detergent, single weight oil. Without knowing the kind of oil they were using, it's hard for me to assume that the same results would be obtained 50 years later with an SL/SM/SN oil.

Could you provide a reference from this century to back up your assertion?

 

[BISCUT]

Originally Posted By: CATERHAM
The mistake in your logic is that while fuel economy may be the motivation in the move to lighter oils, that doesn't automatically translate into increased wear. The move to lighter oils is equally due to improvements in motor oils where a 20wt oil today will have the in service viscosity equal if not greater to 5w30s of 15 or 20 years ago.
Furthermore what happens statistically with a pool of millions of vehicles is absolutely meaningless when it comes down to an individual and how they operate their own car or truck.
I've explained how one fine tunes an oil's viscosity to their own application. And those that do, inevitably realize that the safety margin running a 20wt oil is indeed very high.
What causes increased engine wear is aways abuse, either through ignorance or deliberately and under such conditions a somewhat heavier oil may allow an engine to last longer. But does that apply to the conscientious owner who maintains his vehicle correctly and doesn't ignore service clues like high coolant temp's because he allowed a small coolant leak to go unresolved? Not in the slightest.

To minimize engine wear, run the lightest oil recommended bt the manufacturer, maintain the vehicle corectly and the engine will outlast the rest of the car.



That Sir, brought tears to my eyes! Well said. And I stand by the logic of why trust the engineer to build the vehicle if you don't trust the engineer to spec the oil.

 

[friendly_jacek]

How the oil grade would matter when there is no oil in ring/liner interface on startups (only fuel, condensation and blow by gases)?

If you want to read more, here is a long discussion: https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=118365&page=1

Now, if one wants to dig deeper, there are 3 types of wear and they may behave differently: rings/liner wear, bearing wear, and valvetrain wear. I'm mostly referring to ring/liner wear, but contaminated oil will circulate and produce problems in other components.

 

[Garak]

Originally Posted By: friendly_jacek
The difference was explained by some that low vicosity oils enabled starts at a much lower temp that was harmful to engines and higher viscosity required engine prewarming that was beneficial to engines.


Aside from that, the way I was taught (whether it's actually right or wrong) was that the lighter oil was to aid cranking, along with the possibility of better lubrication at those temperatures, but that the lighter oil was not a replacement for those prewarming methods. Basically, some wonderful, high VI 0w30 might crank quicker and provide better low temperature, cold start protection, that doesn't mean that it's necessarily a wise idea to start it daily at -40 C unaided, either.

Personally, if I have a vehicle outdoors, I plug it in based upon a certain temperature, not based upon what's in the sump. If I'm worried about the oil viscosity, that's what an oil pan heater or my heated garage are for.