Semi synthetic oils

[7Super]

Curious what oil folks are using here, I have a 1999 Vauxhall and manual recommends "semi synthetic" for both engine and live axle. The closest I can find is Castrol GTX high mileage 10w40 which is a blend. And Lucas Oil 75w90 which is fully synthetic for live axle. Are there better options?

[S1Steve]

I don’t know if this is correct for your spec.. I’m a fan of using quality products… Enjoy..

[7Westfield]

I run Brad Penn / Penn Grade in my xflows

Our engine builder loves it, so good enough for me

I even run it in the truck, to simplify inventory

It has extra zinc for flat tappets, if that applies to you

 

I use a generic synthetic for diff      just be sure to get a GL-5 rating

 

MTL is great for most transmissions

[Croc]

10 hours ago, 7Super said:

Curious what oil folks are using here, I have a 1999 Vauxhall and manual recommends "semi synthetic" for both engine and live axle. The closest I can find is Castrol GTX high mileage 10w40 which is a blend. And Lucas Oil 75w90 which is fully synthetic for live axle. Are there better options?

 

If you are looking at a 1999 Caterham build manual then it was written likely in the early 90s (they do not update every year in a company as small as Caterham) with the knowledge of the oil technology of the day.  Synthetic oils were only just starting to come into their own at that time and semi-synthetic was seen as the leading edge thing.

 

I started off using semi-synthetic as thats what Caterham recommended but then Cosworth (who built my engine) shifted to Castrol Edge, a full synthetic, as they thought the oil additives were better at reducing wear.  Caterham took 10 full years to update their manuals.  However, I shifted to the full synthetic when Cosworth recommended. 

 

There is no standard defining semi-synthetic - i.e. the % mix of synthetic base oil to mineral oil.  For all we know it could change % mix each batch.

 

I have always liked the Castrol range since they sponsored me racing in the late 80s/early90s.  Easy to get in the US on Amazon or Walmart or other local places. 

 

So what to get?  First I would make sure you are staying with the correct oil weight per the Caterham manual   Second, you have two choices:

1) If the manual recommends an oil with a zinc additive then choose diesel engine oil of correct weight with added zinc on the label - this is usually for cross flows but not sure what a VX engine needs.  Its a legacy of engines from the leaded gasoline days which the VX engine was (early 1980s) but I know they modified it in the mid-80s with the adoption of unleaded fuel as I remember the ads on TV from then.

2) If the manual is silent on zinc then go best synthetic oil in the range at the correct weight. 

 

For axles, it depends on the car and the type of diff installed.  The 1965 Mustang and my Holdens respond best to dino oil.  The 1973 CSL uses a full synthetic with friction modifiers added) - a legacy of 11 inch wide rear tires through a diff housing the size of a cell phone with only 40% lock .  If you have the standard Ford Sierra diff (including internals) either with or without an aftermarket LSD internal then full synthetic is fine.  If you have the BMW diff (unlikely but...) then full synthetic with friction modifiers added seems to produce best results. 

 

 

 

[Marek]

Two oils widely recommended when looking for high zinc content are Shell Rotella T6 for a synthetic oil and Valvoline VR1 Racing for a mineral oil.  Both are easy to find.

 

Others are available and finding them is a matter of finding spec sheets for the oil.  Motul has excellent options for example, but not so readily available as the Shell or Valvoline.  While I've long had the opinion that Mobil 1 is never the wrong oil, I believe they have reduced the zinc content in recent years and I have stopped using it for my pre-90s cars.

 

Zinc content is a modern topic for classic and vintage cars as late model oil specifications for gasoline engines have reduced the zinc content for reasons I believe are related to change in modern valvetrain designs needed to meet current emissions or mileage expectations.  That all of my 80s engines are known to prefer higher zinc has me always on the lookout for available options.  For years Shell Rotella T6 was marketed as a 'multi-use' oil suitable for gasoline or diesel, but a couple of years ago they dropped the gasoline recommendation but the zinc and phosphorus content on the spec sheet remained unchanged.  The suspicion is the higher zinc required for the diesel specification is too high for some of the latest Long Life oil specifications.  I (and many others) still use it.

 

Oil choices have the aura of witchcraft - not because they are complicated but because consistent information can be hard to find.

[7Westfield]

8 hours ago, Marek said:

While I've long had the opinion that Mobil 1 is never the wrong oil, I believe they have reduced the zinc content in recent years and I have stopped using it for my pre-90s cars.

use the VR1   it has the zinc

 

AFAIK the issue with older engines is down to the cam and tappets, The zinc reduces friction where the lifter "wipes" the cam. Roller tappets solve this.

Guy down the block built a DeSoto 331 for his Model A with roller lifters, and doesn't care about zinc.

 

What I don't understand is how newer OHC engines get around this.....are they all running roller rockers?   Does this mean older OHC engines, like say an old Alfa with bucket tappets should add zinc? 

[wdb]

I recently learned that there are two flavors of VR1; semi-synthetic (I think?) and fully synthetic. Full synthetic comes in black bottles. 

 

I believe the biggest downside of high zinc in modern cars is that it can shorten catalytic converter life.

Edited May 31 by wdb

[Marek]

Yes, the common advice is to use a high-ZDDP oil in your Busso and Nord engined Alfas.

[IamScotticus]

OP, because you mentioned live axle, you aren't thinking of using motor oil in that, are you? Kiss your axle good bye.

Your live axle will use a hypoid gear oil.  

Edited June 2 by IamScotticus

[jbcollier]

Most overhead valve engines do not have direct oil feeds to the cam lobes.  The oil is pressure fed to the rockers which then drip on to the valves, down further to the pushrod holes, lifters and then to the cam lobes.  Some oil is also splashed  about from the crank.  This means it can take a while for fresh oil to reach the cam lobes on a cold start.  ZDDP was a common additive to reduce wear.  It's not the zinc!  That is just part of the molecule carrying the very-useful, phosphorous.

 

This is NOT an issue with overhead cam engines as the lobes run in oil baths and/or are directly pressure fed.  So, you do not need high phosphorus in a Lotus twin cam but you do in a Ford crossflow.

[oilteq]

ZDDP is beneficial any time there is metal to metal contact.  Modern passenger cars are required 600 to 800 PPM phosphorus.  I want more to protect my cam, especially with a performance cam and its increased pressures.  I also want more ZDDP for the timing chain, where some manufacturers have had issues with timing chain stretch.

 

We could also debate oil viscosity.  In 2013, when the only viscosity that would work in a Ford was SAE 5W-20 because of their tight tolerances, I called largest Ford dealer in England (Duningham Motors?) and asked what oil  grade is recommended in the 2.0 Duratec.  I was told SAE 5W-30.  I asked about SAE 5W-20.  After a long pause he said, "But sir, 5W-20 is not available." 

[Vovchandr]

Oh boy. An oil thread. Always a gold mine to see how much of a stickler some people are for things.

 

I don't have much to add other than a few things I remember from selling oil 15 years ago and diving into this hell hole of theoretical discussions and dealing with Geekgeneers on Bobistheoilguy

 

1) There are only 6 or so manufacturers of true synthetic oils. Mobil, Redline, Amsoil and a few others.

2) Everybody else who calls their oil "synthetic" is dino oil that has an additive package that makes it work as good as synthetic but it's not a true synthetic. 

3) Which means that every non true synthetic oil "blend" is just regular dino oil with a "medium" additive package compared to their "synthetic" additive package and that just seems ... wierd to me. Might as well go for the high end package if you're going with a non true synthetic. 

 

I used to be quite a stickler and care for oil pickings and use Amsoil on my bikes. A lot of time has passed and now I just use Mobil1 and change it infrequently and certainly at longer intervals, sometimes same oil sits for years (I assume dangers are moisture content for long sitting oils).

 

I send my oils to Blackstone and usually get a scary feedback everytime. Clearly something is a problem but I doubt it's the oil. 

 

Life is too short to overthink oils for a marginal theoretical gain for regular pedestrian cars and engines. Engines are pretty tolerant. Although high end exotic cars, bikes that rev to 16k or race cars could see the benefit from that marginal gain. 

Edited June 1 by Vovchandr

[oilteq]

It is correct that there are two primary synthetic base oils.  One is built up in a reactor and called PAO (polyalphaolefin) or API Group IV.  The other is a severely refined mineral oil, API Group III.  During the refining process, wax molecules are broken into branched chain paraffins and some of the less stable naphthenic molecules are broken into paraffin molecules.  This molecular rearrangement is why the courts decided it could be called synthetic.

ZDDP works sacrificially, which is why I want more and avoid extended drain intervals.

[pethier]

The most important thing about full synthetic seems to be not what's in it, but what's NOT in it, especially for turbocharged vehicles.

[MRH]

What is reccomended for a 61 S2 differential?  New to the car and changing all the fluids.

Edited June 3 by MRH

[SENC]

3 hours ago, MRH said:

What is reccomended for a 61 S2 differential?  New to the car and changing all the fluids.

This should help with proper weights for all the fluids.  The entire manual is in the library, should you need it.

 

 

I've been using Redline motor oil, gearbox oil, and diff fluid for years in my Seven and Elan.

Edited June 3 by SENC

[MRH]

Thanks.  Oil is 20w50 Driven Racing Oil GP-1 (recommended by Ivey), trans is redline, will get the gear oil next.

Edited June 4 by MRH