Oil ..no not again

[trchris]

Hi all

For those who might be interested Im just about to order some more engine oil from Westway and have noticed they now advertise 15w50 semi synthetic high ZDDP ( 1500ppm) oil , as l understand it gives better cold start protection at a very good price for 5 lts

Chris

 

[Andy Moltu]

I've used their semi-synthetic 20-50 for a few years. Swapped to them when the likes of Millers got pricey in the way that Penrite did a few years previously.

[harrytr5]

For what the oil is made for I will stick with Penrite Classic Light 20/60. The cost is of course a huge factor but then is a engine rebuild.

Does not mean I am right but will stick to what I use.

Regards Harry.

[RogerH]

Hi Harry

I have the same thoughts as you.

How much is a rebuild - how much is the more expensive quality oil.

Roger 

[Ian Vincent]

31 minutes ago, RogerH said:

Hi Harry

I have the same thoughts as you.

How much is a rebuild - how much is the more expensive quality oil.

Roger 

+1, or is it +2. 

The cost of oil and filters is in the noise for me once you decide to have a classic car. And I do all my own maintenance so there are no labour charges. 

And FWIW, when I take my daily driver for its annual oil change (as recommended in the manual) the oil on its own costs nearly £100. 

Rgds Ian

[Steve-B]

The cost of real oil is minuscule compared to the cost of a rebuild. Keep an eye out and you can find Miller’s 15/50w on sale regularly. Nabbed 10l on sale for almost 1/3rd off over the winter. My 6 doesn’t use a lot, but having a stock on hand is prudent.

[Andy Moltu]

One concern with wider viscosity range oils is whether this is achieved by using more viscosity modification additives that might not work as well in the long term as the modifiers break down.

This was a concern regarding very cheap 20w50 back in the day. 
 

This raises the question as to what is a quality oil?

Big marketing budgets?

Offering their products to the classic car traders at a big discount?

From what I can gather Westway supply decent products but don’t spend as much on marketing as some of the bigger names.

 

 

[Peter Cobbold]

Which definition of "1500 ppm" are Westway using:

is it "1500 ppm Zinc as ZDDP"

or

"1500ppm ZDDP."

When TRs were new the oils were all "1500 ppm Zn as ZDDP".   Nowadays the switch to "1500 ppm ZDDP" means the actual concentration of the ZDDP molecules in the oil is about seven-fold lower. Why? because zinc contributes about one seventh of the mass of the molecule. That lower ZDDP level allows the oil to be used without poisoning the catalytic convertors in modern classics.

Peter

 

[trchris]

Hi Peter 

They are claiming on the spec sheet 

15w50 semi synthetic 

API SG, SH,SJ

1500ppm zinc

1450ppm Phosphorus 

6482ppm sulphur 

All in a non fancy blue 5ltr container

Chris

Edited April 11 by trchris

[Phil Kirk]

Many many moons ago our old Forum stalwart, Alec Pringle suggeted to me to use Siloleen Superlube 20w50 in my TR6. I have done with no issues. I change the oil once a year before the winter lay up.

Phil

[michaeldavis39]

 Good deal on Opie Oils for Valvoline VR1 20w50- just ordered 2 x 5litres inc delivery for £60 

[TR Rob]

1 hour ago, michaeldavis39 said:

 Good deal on Opie Oils for Valvoline VR1 20w50- just ordered 2 x 5litres inc delivery for £60 

+1

[PriceLes]

Once my new engine (which got 4 packs of Penrite Classic in 12 months, whereabouts unknown) is run in it will get Royal Purple HPS 20/50. 
Although not an air cooled engine it performed well in Jim Comstock’s scar tests some years ago so should perform well in the TR if not better being water cooled.

 

Edited April 15 by PriceLes

[trchris]

Had a message from Westway regarding this oil and was informed that if you’re suffering from low oil pressure when hot it’s an upgrade on the mineral 20w50 and they also supply 20w60 . I’ve no connection with them just thought I’d mention to anyone interested 

Chris

[Lebro]

I have noticed an intetesting thing with Westways synthetic.  When hot I get a higher oil pressure at 2000 RPM than when cold. 

Bob

[Ian Vincent]

6 hours ago, Lebro said:

I have noticed an intetesting thing with Westways synthetic.  When hot I get a higher oil pressure at 2000 RPM than when cold. 

Bob

I get that as well Bob, have for a long time. 

When I first start the indicated pressure is about 55psi at any revs and then as the engine warms up the pressure at 2000 rpm goes up to 70psi and it drops to about 30psi at 700 rpm. 

Rgds Ian

[TRTOM2498PI]

On 4/11/2026 at 9:47 AM, harrytr5 said:

For what the oil is made for I will stick with Penrite Classic Light 20/60. The cost is of course a huge factor but then is a engine rebuild.

Does not mean I am right but will stick to what I use.

Regards Harry.

Great oil choice, Harry. Use it myself.

[Don H.]

On 4/12/2026 at 3:57 AM, Lebro said:

I have noticed an intetesting thing with Westways synthetic.  When hot I get a higher oil pressure at 2000 RPM than when cold. 

Bob

The viscosity index modifiers in the multigrade oil are definitely earning their pay.

[Don H.]

On 4/11/2026 at 12:14 PM, michaeldavis39 said:

 Good deal on Opie Oils for Valvoline VR1 20w50- just ordered 2 x 5litres inc delivery for £60 

 That's a pretty good price for your market, I'd say.  I just got 10 quarts (US) / 9.5 L of SAE30 Valvoline VR1 for about £52 delivered here in the southwestern US.

The SAE30 grade of VR1 is reported by Valvoline to have 1400ppm Zn (as Zn).  It's in my car's engine and gearbox.

https://sharena21.springcm.com/Public/Document/18452/18bdee61-0a7e-e711-9c10-ac162d889bd3/25174f93-e29c-e711-9c10-ac162d889bd3

[Peter Cobbold]

On 4/11/2026 at 5:53 PM, trchris said:

Hi Peter 

They are claiming on the spec sheet 

15w50 semi synthetic 

API SG, SH,SJ

1500ppm zinc

1450ppm Phosphorus 

6482ppm sulphur 

All in a non fancy blue 5ltr container

Chris

Hi Chris, That's a very good concentration of ZDDP, correctly defined. Peter

 

[john.r.davies]

But it's not the Zinc that protects heavily loaded surfaces, it's the Phospate in Zinc dithiophosphate!   The Zinc is just there for the phosphates to ride on:

But i suppose that the Zinc concentration is easier to measure.

John

Edited April 15 by john.r.davies

[Peter Cobbold]

On 4/15/2026 at 1:49 PM, john.r.davies said:

But it's not the Zinc that protects heavily loaded surfaces, it's the Phospate in Zinc dithiophosphate!   The Zinc is just there for the phosphates to ride on:

But i suppose that the Zinc concentration is easier to measure.

John

Hi John,

It is indeed zinc that is measured, but the R groups add seven times the mass of  zinc to the entire ZDDP molecule. And the oil companies have exploited that to allow some classic oils to ne cat-safe ( phosphate poisons cats).

The R groups add a large mass to the ZDDP molecule. So some oils use that mass to seemingly boost the 'ppm' number. The R moiety is variable, and can give seemingly impressive "ppm ZDDP" ,but its a hollow claim. The correct way , in force when TRs were new, is to state the level as the ppm of zinc. To distinguish Zn in ZDDP as opposed to othe sources, the mass of Zn is given "ppm Zn as ZDDP".  

The difference between ZDDP contents is large, for the same number, because zinc itself accounts for , typically, only one seventh of the mass of the ZDDP molecule. So an oil with say "1400ppm ZDDP" has only "200ppm Zn as ZDDP". 

The devil is in the detail.

Peter

[john.r.davies]

Thank you, Peter!  Clear as fresh oil!

But not the last bit.  "ppm" = 'parts per million", which I interpret as a concentration, of a molecule, in this case ZDDP.  There's only one atom of Zinc per molecule, however long the R hydrocarbon chains.    So how are the PPM different for the molecule and the Zinc.

I ask to be taught, not to challenge!

John

Edited April 19 by john.r.davies

[Peter Cobbold]

On 4/19/2026 at 8:50 PM, john.r.davies said:

Thank you, Peter!  Clear as fresh oil!

But not the last bit.  "ppm" = 'parts per million", which I interpret as a concentration, of a molecule, in this case ZDDP.  There's only one atom of Zinc per molecule, however long the R hydrocarbon chains.    So how are the PPM different for the molecule and the Zinc.

I ask to be taught, not to challenge!

John

Hi John,   The trick recent suppliers use is to confuse the contribution the mass of zinc makes to the molecule with the mass of the entire molecule. Let's take a typical molecule of ZDDP in which the R chain's mass is about 7 times the mass of the zinc. Atomic mass of zinc is 65 so the whole molecule including the zinc will be 520.  So  for say 1400 ppm of the whole molecule the zinc-alone ppm will be 1400 x 65/520 = 175ppm. This trick by the oil companies is an attempt to hide the much lower concentration of the molecule. because years ago they quoted only the mass of the zinc atom. Thus a correctly specified oil would have around "1400 ppm Zinc as ZDDP". That means the ppm of the whole molecule would be 1400 x 520/65 =  11200 ppm. That is actually the true level of the whole molecule, but it was never used on labels. The difference 1400 vs 11200 is considerable.   ZDDP does not influence oil pressure - its an anti-scuff agent- how are we to know our cam-followers, rocker/valve and rings are protected?

Curiously I am into zinc re Parkinson's - lDOPA binds zinc, and depletes pwPD of zinc. And most of the non-motor symptoms of PD resemble those caused by dietary zinc deficiency! The drug is as old as the TR6... and this problem is only now being uncovered! 

Peter

[john.r.davies]

NO More tHan 25mgs/day, according to the NHS