Older vehicles=thicker oils

[Capa]

Happy New Year! I am wanting to know if this is a myth or reality. It is said that as vehicles age and get older that eventually one will have to bump up the thickness of the oil. I noticed that on the BITOG homepage that this is what Dr Haas says. I have also read it many times in different auto forums. It is a very common assumption but is it true?

I am wondering, since I dont have an oil gauge, whether you all who do have oil gauges have noticed a difference as your vehicles age? According to Dr Haas, this is one way to tell. Also, I am wondering how big of a difference there is on a gauge if, for example, the vehicles calls for a 5W-30 and you try 5W-40 or 5W-20? Thanks for reading and I look forward to your replies.

 

[Artem]

My 98 Toyota Camry V6 that I had since new has 212,000 miles. I'm still using the same 5w30 viscosity I've been using since day 1. Oil consumption has been about half a quart per 5,000 miles since as long as I can remember. Engine runs great and produces good UOA reports.

I honestly don't see any reason to just one day decide to switch to a thicker oil. Unless you're burning massive amounts of oil, stick with what the owners manual recommends.

 

[ahoier]

Raising the viscosity seems like a band-aid to me.....I'd always go with the manufacturer recommended oil weight.....but that's just me.

Still using 5W-30 in my 88 Dodge Aries.....since my last oil change, I've topped off maybe 1/2 a quart....and I'm at my 2k mark (typically go 3k....) - one of these I'll get a UOA and see how she reads....hehe.

 

[XS650]

Originally Posted By: ahoier
Raising the viscosity seems like a band-aid to me.....I'd always go with the manufacturer recommended oil weight.....but that's just me.

Still using 5W-30 in my 88 Dodge Aries.....since my last oil change, I've topped off maybe 1/2 a quart....and I'm at my 2k mark (typically go 3k....) - one of these I'll get a UOA and see how she reads....hehe.


Yes, it is a bandaid.

Assuming an oil pressure gauge is accurate (a big assumption) low oil pressure could be caused by several things other than engine wear. Oil pump wear for instance.

Also, a person would need to know what oil pressure is acceptable for their engine. The old 10psi/thousand rpm that gets tossed about is only an old rule of thumb.

 

[Ken2]

The choice of oil viscosity relates to the size of the oil gap in the bearings, among other things. If the oil gap widens due to wear, you'll see a drop of oil pressure. Higher viscosity oil will be a help. Modern engines wear very little, even with a coupl'a hundred thousand miles on then. Maybe one grade higher vis in hot weather or very heavy towing might be prudent on very high mileage engines, otherwise, don't worry about it.

By the way, Dr. Ali E. Haas is a cosmetic plastic surgeon, not a mechanical engineer nor a tribologist. Take his recommendations with a grain of salt.

 

[CMMeadAM]

It might do you well to look further into the qualifications and resume of Dr Hass. He and his accomplishments are far
from those of just a "cosmetic plastic surgeon"... which is
a most credible accomplishment in an of itself.

I would suggest most read and think about HIS comments and recommendations and take TOURS with even lESS than a "grain of salt."

 

[Capa]

To be fair, it isn't just Dr Haas who mentions going to a thicker oil as a vehicle ages, it's repeated over and over in different car forums.

I would love to hear from someone with an oil gauge.

 

[mechtech2]

Bearings do wear slowly [at least they should!].
Rings and bores more so. Thicker oil helps with oil use/burning.
Some engines can see a benefit from a grade up in 75,000 miles, and some in 200,000+.

A good option is a high mileage oil. They are on the thick end of their viscosity range, with seal softeners/conditioners.

 

[JimPghPA]

My 1985 Olds 88 with 5 Liter Gas engine that has 168K miles will stall if I use a XW-30 in it on a hot day, but it ran fine on Xw-30 for many years. I now run 20W-50 in it and have no problems except that the 20W lower number limits me to not starting it if ambient is below 15 F.

 

[OVERKILL]

Originally Posted By: JimPghPA
My 1985 Olds 88 with 5 Liter Gas engine that has 168K miles will stall if I use a XW-30 in it on a hot day, but it ran fine on Xw-30 for many years. I now run 20W-50 in it and have no problems except that the 20W lower number limits me to not starting it if ambient is below 15 F.


Interesting. I've run everything from 0w20 (winter) to 5w50 in my similar vintage 302's and they don't "respond" in any manner that affects how they drive. They are a bit quieter on the heavier grades and so I use 0w40 or 5w40 in them now. Both have over 200,000 miles on them.

 

[CATERHAM]

Older engines don't automatically require a heavier oil.
In a well serviced engine, bearing wear may still be negliable after 500,000 miles or more consiquently a higher viscosity oil is not necessary.

A while back I posted the range in oil pressure at operating temp's of 10 different oils ranging from the very light Toyota 0W-20 to a M1 0W-50 here (half way down page 5):

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2276634&page=5

The comparison was made in my Caterham where the spec' oil is a 5W-40. The comparison was made at 6,500 rpm and sump oil temp's of 95C. They ranged from 65 psi (used Toyota 0W-20) to 92 psi for a 5W-50. M1 5W-30 and PP 5W-30 had a OP of 78 psi and M1 0W-40 an OP of 86 psi. RL 5W-30 an OP of 87 psi.
Another oil I've tested is the Idemitsu 0W-20 which has OP of 69 psi.
With the 0W-20 Idemitsu oil, at 70C oil temp's the OP is 92 psi or just below the oil pump by-pass point. From memory with the M1 5W-30 I needed oil temp's of at least 85C to be able to use maximum rev's without the oil pump going into by-pass mode.

The main point of the thread was that OP correlates with the HTHSV rating of an oil assuming similar VIs (within 15 points or so).

Obviously different engines will have somewhat different OP readings but the percentage difference between the oils should be close.
If the spec' oil is a light 30wt like M1 or PP it's very unlikely you'd be testing the minimum oil pressure spec's for an engine by running a 0W-20 or 5W-20 oil unless very high oil temp's are acheived or massive fuel dilution. The higher than necessary OP with the specified grade is the safety margin to deal with such unforeseen occurances that can unduly lower the viscosity of an oil including oil shear.

One of the advantages of using a lighter than spec' oil is that you can use higher rev's when the oil is not fully up to temperature without the oil pump going into by-pass.
One of the main disadvantages of running a heavier than spec' oil is that you may never be able to use max' rev's without going into by-pass mode which would be clearly counter-productive from a lubrication efficiency view-point.

 

[Artem]

Yep, what CAT said.

 

[Doug Hillary]

Hi,
CATERHAM - Your comments are very relevant. As you well know I am very wary of recommending to Mr Average Motorist the use of very light viscosity lubricants that are outside a Manufacturer's recommendations. This has much to do with the minimum HTHS viscosity set by certain engine Manufacturers

That said, I used a 5W-40 synthetic in my heavy diesel engines along with synthetic media FF filters ((later only 40micron SS screens) and a centrifuge for the reasons you allude to.

Getting around 60 litres of coolant and lubricant up to a suitable operating temperature can take a very long time indeed. In my case up to and beyond 30 minutes on average. Compared to a 15W-40 HDEO and a cellulose filter the temperature difference for filter flow was around 60-30F less in my case

Using SS screens instead of barrier media ensured correct and maximum flow soon after startup

 

[SS1970chrysler]

Originally Posted By: JimPghPA
My 1985 Olds 88 with 5 Liter Gas engine that has 168K miles will stall if I use a XW-30 in it on a hot day, but it ran fine on Xw-30 for many years. I now run 20W-50 in it and have no problems except that the 20W lower number limits me to not starting it if ambient is below 15 F.

I had probably the same car, an 85 Delta 88 w/307 4bbl. At around 90k, it started running rough at idle with 10w-30 after the 1st couple thousand miles each OCI. I switched to 10w-40 or 15w-40 and the problem never recurred.

 

[aquariuscsm]

What about high performance cars that spec a thicker oil for extended high speed driving and/or racing (40 or 50 weights)? Will thinner oils shorten the lifespan of the engine if the car is raced or driven fast regularly,etc on thinner gas-mileage oils (5/10W30)?

 

[CATERHAM]

Hi Doug,

Happy New Year!

Yes I agree, it's generally not wise to deviate from the manufacturers spec' oil recommendation for various reasons unless you have a very good reason for doing so. And the more information available to you the better. A fully operational oil pressure guage can provide a wealth of info' on the viscosity characteristics of an engine for a given application. A oil temp' gauge while not imperative is nice as well to determine if viscosity variation is 100% related to temperature or not.

With the installation of oil gauges, one should take the time to see how much the OP and OT varies over the most extreme operating conditions as possible or that you'll likely encounter. If your OP seems higher than necessary all of the time, first try an oil with as low a HTHSV and as high a VI as possible of the recommended oil choices and minimum recommended oil grade.
If you still want to try something lighter, hopefully by this time you will have become very familiar indeed with the operational viscosity characterisctics of your engine.
I don't want to sound too cautious in optimizing the oil viscosity to your own application; it is after all better to be safe than sorry.
Having said that, I will say that for street use it is quite difficult to actually run an oil that is too light if you have an OP gauge. On the off chance that the OP was a bit lower than expected for whatever reason, you'll know it as it happens and can take remedial action. Simply driving more conservatively usually gives you the additional OP you'd like and you can take it from there.

 

[troyb43]

Originally Posted By: JimPghPA
My 1985 Olds 88 with 5 Liter Gas engine that has 168K miles will stall if I use a XW-30 in it on a hot day, but it ran fine on Xw-30 for many years. I now run 20W-50 in it and have no problems except that the 20W lower number limits me to not starting it if ambient is below 15 F.


Might think about Amsoil ARO (20W-50), that should be good down to about -13F.

 

[CATERHAM]

Originally Posted By: troyb43
Originally Posted By: JimPghPA
My 1985 Olds 88 with 5 Liter Gas engine that has 168K miles will stall if I use a XW-30 in it on a hot day, but it ran fine on Xw-30 for many years. I now run 20W-50 in it and have no problems except that the 20W lower number limits me to not starting it if ambient is below 15 F.

Might think about Amsoil ARO (20W-50), that should be good down to about -13F.

A 20W-50 is obviously overkill.
Short of install an OP gauge a 5W-40 or 10W-40 would likely restore adequate OP as SS1970chrysler alluded. Or a 50/50 5W-30/wt blend. Obviously you don't want to run an oil heavier han necesary.

 

[semaj281]

Originally Posted By: SS1970chrysler

I had probably the same car, an 85 Delta 88 w/307 4bbl. At around 90k, it started running rough at idle with 10w-30 after the 1st couple thousand miles each OCI. I switched to 10w-40 or 15w-40 and the problem never recurred.

Based on this testimony I'd give Shell Rotella 15w-40 a try.
It's a highly regarded oil for older engines that consume oil.

 

[Capa]

Caterham, it seems that you've been keeping track of your oil pressure numbers with different oils. Have you seen any kind of drop in the OP as the engine has aged in any of your vehicles?

Doug, it's good to hear from you! Are you saying that you have run oils thinner than what the manufacturer has spec'd?

So are we all saying that more than likely for the modern engine this idea about as it ages to go with a thicker oil is a myth?