20W-50 Engine Oil Comparison

I’ve recently discovered that there’s a lot more things to consider when choosing the right engine oil for a classic car than just the grade, e.g. 20W-50.  These subtle differences can make a significant difference to not only performance, but more importantly the life of the moving parts of the engine –  a major consideration for me, since my classic car is a daily drive.

One key aspect that I’ve discovered was related to the amount of Zinc DialkylDithioPhosphate (ZDDP) present in the oil.  As a simple summary, this helps the lubrication of moving parts that rub together, and was an essential factor in oils back in the days.  However, this has been reduced over time, mainly due to the adverse effect of ZDDP on catalytic converters in later cars, but it turns out this is understood by many “quality” oil producers, who ensure this is still added to protect classic cars.

Duckhams have written an excellent article about ZDDP, which can be found here, and I have compiled a table of popular engine oils, listed in order of my personal favourites.  My consideration has been the balance between Viscosity (VI), Performance (API), ZDDP (measured in parts-per-million),  the level of Detergent, and price (not shown, as this can vary).

If you want to know more about the API standards, please  click here for the section of the API website detailing different oil categories, and here for an excellent news article on the Rymax Lubricants website explaining how the API specification works.

I hope this is useful, and wonder if you’ll share my surprise when you realise that the “quality” of some very well-known engine oil brands may not quite be as you had thought!

DetergentData Sheet
Millers Classic Pistoneeze 20w50133SJ1130High
Fuzz Townshend Classic Oils Heritage 20W50131SL/CH1300High
Duckhams Classic Q20W-50135SJ/CE1300Med.
Penrite Classic 20W-50125SL/CF1080Med.
Castrol Classic XL 20W-50124SF/CC800Low
Morris Lubricants
Golden Film
Motor Oil
Comma Classic 20W50

MGB GT Clutch Types

It turns out there are two clutch types available for the MGB GT…

The standard version, HK9649, (see pic below, which features the carbon thrust bearing), and the heavier duty type, HK9679.

Here’s the summary…

HK9679 (Heavier Duty Version):
Heavy Duty Fits all 63-80 MGB’s & MGB GT’s.

This clutch has stronger pressure plate diaphragm springs. The clutch disc is heavy duty as well. Also comes with a ball-bearing type clutch release bearing. This clutch will withstand heavy duty or high-performance use.  =Suitable For MGB & MGB GT Fitted With 1800cc Engine.  1971 – 1981. Clutch Size 204mm (Heavy Duty Ball Release Bearing)
The HK9679 has smaller driven plate friction linings as the larger linings were prone to judder.
The reference numbers of this kit are…
    – HE3517 cover assembly
    – HB8752 driven plate.
    – HD9108 roller release bearing
HK9694 (Standard Version):
Includes the pressure plate, disc, and release bearing. It will fit any 1963 – 1980 MGB or MGB GT. These clutches are a little bit cheaper than HK9679 clutches.
The HD may be referring to Heavy Duty, as the standard version of the kit; HK9694 which has a different cover, drive plate and the old type carbon release bearing (HD3317).
The HK9694 reference numbers are…
    – HE3331 cover assembly.
    – HE9711 driven plate.
    – HD3317 carbon release bearingThis is the second time in five years that the carbon thrust bearing has shattered, and I wonder if the judder mentioned above has anythng to do with it.  The first I suffered this issue was soon after I purchased the car, (it hadn’t been driven much prior to my purchase), and then again the other day after not being driven for a year.  Whilst I can’t tangiblhy prove this, I also wonder if the standard carbon bearings don’t like being laid up, and maybe seize up if not driven regularly. Please note: I don’t know what make the original (shattered) clutch was, so the picture of the Borg & Beck clutch is for reference only.
My recommendation, however, if you’re a daily drive like me, is to go with the HK9679, as this seems to the heavier duty version.
I’ll update this blog on how it goes…

Engine out…

A few days after returning home, back luck struck, whereby the carbon clutch bearing had shattered/disintegrated.  I don’t know what caused this, so I can only put it down to being laid up for a year and something seizing up.

So, using the opportunity while the local garagae, (Church Garage on Stockbridge Road in Winchester), had the engine out, I managed to get the day off, and went there armed with paintbrush in hand…

Before… flaky red paint.. just a mess really!


After… Racing Green… It’s a complete transformation… loving it! 🙂

Engine bay… stay tuned!

Back home :)

MOT Day… Passed first time… no advisories :)

Happy days!!!

After a year of hard work, this is a superb result!

Back inside for polishing & tidying

Getting there!

Fired up for the first time in a year…

Front assembly & bumpers

Headlights, bumpers, rear lights & interesting wiring!