Geardo

Royal Purple HPS 10w-30, and a K&N filter

Biker

1986 with 61k miles. Use Penzoil or Quaker 10-W30.

mickey5

My '90 only sees about 500 miles a year in the summer. It now has 44K miles on the clock. Whats your opinion on how often to change the oil? I have always used GTX Dino. Engine doesn't burn any or smoke...even on startup. Your thoughts would be appreciated.

Nathan Plemons

Even the oils with the extremely high change intervals recommend xx,xxx miles or 1 year. If you drive it that infrequently, I would probably change it every year just on GP. How much does it really cost to change the oil if you're using conventional anyway?

Cavi

Change your oil once a year before you're driving season and go to synthetic

tombrammer

http://www.gmhightechperformance.com...l/viewall.html
good read!
I personally would never use syn. in an older car. But the LT1 came with it from the factory because of the switch away from an engine oil cooler and the LT1's higher operating temps, fan doesn't even come on until 230 degrees, I would never use reg oil in an LT1 unless it was rebuilt with reg. oil in mind (open bearing clearances and reprogram fans to come on at lower temps).

daca

Paul Workman

Thanks for the link. I recon it didn't add much besides confirmation of what some have said here re synthetic, except for possibly adding 3-5 hp to the rear wheels: NO small thing when one consideres the $$ one might spend on increaseing the TB at a cost of $300-$400 (perhaps) for about the same HP lift!

Interesting stuff, this entire thread...

P.

daddysvet92

So I read all of the comments and comparison's, but when I decide to purchase the brand of oil, should I buy 5 or 10w30.
I know that the recommended is 5w30 for my 92, is tis what I should use or go to 10w30, and if so Why?

Thanks

C66 Racing

Unless you get the exact specs for the brand of your choice, or unless you live where it gets really cold (like -20C cold - which you might up there in Ontario) - it is really hard to answer this question.

At normal temps, both a 5w30 and a 10w30 are 30 grade oils. That means they have to have a viscosity of 9.30-12.49 cSt at 100C (212F) and have a minimum high temp high shear viscosity of 2.9 cSt at 150C (300F).

A 5w30 and a 10w30 have different cold specs. A 5w30 must have a Brookfield pumping viscosity less than 60,000 cP at -35C (-31F), and a Brookfield cranking viscosity less than 6,600 cP at -30C (-22F). A 10w30 must have a Brookfield pumping viscosity less than 60,000 cP at -30C (-22F), and a Brookfield cranking viscosity less than 7,000 cP at -25C (-13F).

A simplistic view would be that both a 5w30 and a 10w30 are the same at normal - high temp and the 5w30 flows better than a 10w30 at very cold temps.

A more detailed look reveals that the viscosity bands are so wide you don't always get what you expect.

Take two cases.
Mobil 1 5w30:
40C: 61.7 cSt
100C: - 11.0 cSt
150: - 3.1 cSt
Pour Point: -42C

Mobil 1 10w30:
40C: 63.2 cSt
100C: - 10.1 cSt
150C: - 3.0 cSt
Pour Point: -42C

According to Mobil 1's posted data (above from their product data sheets), contrary to what you'd expect, the 10w30 provides a lower vice a higher viscosity at both 100C (212F) and 150C (300F) than does their 5w30. Based on that, if you believe their data, I'd use the 5w30 in all cases as you get better flow when cold and better high temp protection when the oil is very hot.

AMSOIL Signature Series 5w30:
40C: 60.3 cSt
100C: - 10.5 cSt
150: - 3.2 cSt
Pour Point: -51C

AMSOIL Signature Series 10w30:
40C: 62.9 cSt
100C: - 10.5 cSt
150C: - 3.2 cSt
Pour Point: -48C

In AMSOIL's case (for their top tier street oils), the 5w30 and 10w30 are exactly the same at high temp and the 5w30 flows better at low temp - I'd still probably use the 5w30 for the street.

If you look at the specs for different brands, you'll get different results.

In cases of very cold winters, I'd consider a 0w30 for the winter as it is still a 30 grade when hot, but flows even better than a 5w30 when really cold.

Final discussion point is viscosity improvers. To make a 5W-30 oil, one starts with a 5W oil and adds viscosity improvers. These VIs have the property that in cold temperatures their polymers coil up, contributing little to the base oils viscosity measurements. At higher temperatures they uncoil to reduce the base oil's loss of viscosity as it heats up. So when the VIs break down (shear down) one is left with properties of the original base oil (the 5W stuff). Thus over time, a low quality 5w30 could over time shear down to a 5w20, or worse. Good synthetics do not need as much VI as conventional oil so in general don’t shear down as fast. Since a 10w30 will need less VI than a 5w30, again in general it will perform better under shear forces since there is fewer VI to shear down and there is proportionately more basestock in the 10w30 since it isn’t being displaced by VI. The shear down of VIs is why most race oils are 10w30 vice 5w30 or 0w30 - they have little to no VIs thus can't attain a 5w30 or 0w30 rating. But with little to no VIs, the oil is very shear stable and will retain its viscosity as the oil experiences shear forces. This is also why the ZROD 10w30 I listed above is a 10w30 vice a 5w30 or a 0w30.

If you do opt for a 10w30 - be careful with oil warmup. A 10w30 will not flow as well as a 5w30 or 0w30 until it is warm. My personal rule of thumb is to keep rpm low and not to get into the throttle hard until my oil is about 150F.

daddysvet92

Thanks Subdriver!
What a write up... 5w30 it is!

Thanks again...

biggrizzly

Brad Penn 10W40
http://www.penngrade1.com/Products/H...SAE-10W40.aspx

Dracule

In everything I'v owned lately, I'v used Synthetic. There's logic to Retired's post, but beyond the ring lands poor sealing if coked up by dino carbon, I'd use the Synthetic. As for the sealing properties, I believe 'Lucas' makes an adative just for that.

I'v read the sealing horror stories about 'he said, she said', but I'd like to know just 'who' actually 'did' have leaks occur? Lots of stories, lots of bench racers in their barko'loungers giving 'sage advice' based on what 'somebody else said' with no actual experience. I'v used it in everything. I change it at about 4K or so, or by color. Its relatively cheap insurance as it were. And there has 'Always' been a performance increase I could 'hear and 'feel', I'd use Synthetic.

Dracule

I'll also add, .......I dont think breakdowns can wholey be pointed to, as by choice of a particular oil for the most part........ rather, The Lack of OIL seems the problem more often.

Nathan Plemons

I run 10w30 for the reasons listed above. It doesn't get very cold here and my car is garage kept. I tend to drive my car hard so the less amount of my oil is additive and the more is actual lubrication, the better.

FOURSPEEDVETTE

At normal temps, both a 5w30 and a 10w30 are 30 grade oils. That means they have to have a viscosity of 9.30-12.49 cSt at 100C (212F) and have a minimum high temp high shear viscosity of 2.9 cSt at 150C (300F).

A 5w30 and a 10w30 have different cold specs. A 5w30 must have a Brookfield pumping viscosity less than 60,000 cP at -35C (-31F), and a Brookfield cranking viscosity less than 6,600 cP at -30C (-22F). A 10w30 must have a Brookfield pumping viscosity less than 60,000 cP at -30C (-22F), and a Brookfield cranking viscosity less than 7,000 cP at -25C (-13F).

A simplistic view would be that both a 5w30 and a 10w30 are the same at normal - high temp and the 5w30 flows better than a 10w30 at very cold temps.

A more detailed look reveals that the viscosity bands are so wide you don't always get what you expect.

Take two cases.
Mobil 1 5w30:
40C: 61.7 cSt
100C: - 11.0 cSt
150: - 3.1 cSt
Pour Point: -42C

Mobil 1 10w30:
40C: 63.2 cSt
100C: - 10.1 cSt
150C: - 3.0 cSt
Pour Point: -42C

According to Mobil 1's posted data (above from their product data sheets), contrary to what you'd expect, the 10w30 provides a lower vice a higher viscosity at both 100C (212F) and 150C (300F) than does their 5w30. Based on that, if you believe their data, I'd use the 5w30 in all cases as you get better flow when cold and better high temp protection when the oil is very hot.

AMSOIL Signature Series 5w30:
40C: 60.3 cSt
100C: - 10.5 cSt
150: - 3.2 cSt
Pour Point: -51C

AMSOIL Signature Series 10w30:
40C: 62.9 cSt
100C: - 10.5 cSt
150C: - 3.2 cSt
Pour Point: -48C

In AMSOIL's case (for their top tier street oils), the 5w30 and 10w30 are exactly the same at high temp and the 5w30 flows better at low temp - I'd still probably use the 5w30 for the street.

If you look at the specs for different brands, you'll get different results.

In cases of very cold winters, I'd consider a 0w30 for the winter as it is still a 30 grade when hot, but flows even better than a 5w30 when really cold.

Final discussion point is viscosity improvers. To make a 5W-30 oil, one starts with a 5W oil and adds viscosity improvers. These VIs have the property that in cold temperatures their polymers coil up, contributing little to the base oils viscosity measurements. At higher temperatures they uncoil to reduce the base oil's loss of viscosity as it heats up. So when the VIs break down (shear down) one is left with properties of the original base oil (the 5W stuff). Thus over time, a low quality 5w30 could over time shear down to a 5w20, or worse. Good synthetics do not need as much VI as conventional oil so in general don’t shear down as fast. Since a 10w30 will need less VI than a 5w30, again in general it will perform better under shear forces since there is fewer VI to shear down and there is proportionately more basestock in the 10w30 since it isn’t being displaced by VI. The shear down of VIs is why most race oils are 10w30 vice 5w30 or 0w30 - they have little to no VIs thus can't attain a 5w30 or 0w30 rating. But with little to no VIs, the oil is very shear stable and will retain its viscosity as the oil experiences shear forces. This is also why the ZROD 10w30 I listed above is a 10w30 vice a 5w30 or a 0w30.







OK. Now there will be a written exam on this information.

Chuck Tribolet

Like the OP, I use Castrol GTX 5W30 in my '87. It only gets driven
about 2K miles a year, mostly to Tucson to see my mom at Christmas.
I change the oil once a year. Why Castrol GTX? I tore down the
engine in my 240Z at 100K miles (broke the tip off a valve stem
because the tach was reading about 500 RPM low.) As I tore it down,
I checked all the clearances and they were within spec for a NEW
engine. I'd always run Castrol GTX, and don't see a reason to change.

Jbws86928

Mobil 1 5w-30

ken1950

Mobil 1 10/30

RACER 1993

I use Mobil 1 in all three of my vehicles. When you do it yourself it really doesn't cost much more.

I have been using synthetic oils for about 30 years. Started out with AMZOIL and then went to Mobil 1. No problems.