Thread: What Oil do you use for the P38!!

Originally Posted by kapowww

Yes still many differing opinions on both sides makes me more confused!

Ok how about I say I'll choose Castrol as it's been good in all my other cars, and I'm leaning towards CASTROL GTX HIGH MILEAGE 15W-50 (for GEMS HSE 233,000km). Anything negative about my choice?

No not at all. A good choice actually if Castrol is your brand.

Castrol has a good solid reputation, so if you're happy with it and the right price, you can't go wrong there.

Originally Posted by redandy3575

You'd be surprised what a difference it can make.

Synthetic oils are usual lab manufactured and made in a more sterile environment so as to endure, clean & trap contaminants lasting a lot longer than many mineral based oils, which if you start out from new with Full synthetic oil, you can if you desire go the distance of doing oil changes as per the P38 12months/20000km interval of the owner manual.

The seals will set (over time) into those oil. Where's the mineral oils having a slightly more impurity level can and will react with the seals in the long term if a sudden change from synthetic to mineral, or vica versa is made. The seals will usually only set once not twice. Though having said that, it may not be an issue with the latest cars and their engines as they May have altered the designs & methods of making their new gaskets and seals in recent times. However the Rover V8 is certainly not a late modern design as we all know, with the engine dating back some 30 plus years.

But, don't just take my word for it, most specialist Land Rover mechanics will just about tell you the same thing.

I may stand corrected on the detergent side of things, but have been advised with mineral based oils to be more vigilant with more regular oil changes to prevent the oil from breaking down sooner and forming a black sludge build up if not attended to.

Therefor in relation to the original question, a good quality semi-synthetic oil is a safer balance if unsure of the engine history.

Err, no.


Please have a read here Oil Type You Guys Use? - Defender Forum - LR4x4 - The Land Rover Forum and here Oil Type You Guys Use? - Page 2 - Defender Forum - LR4x4 - The Land Rover Forum on oil characteristics I believe are suitable for the Rover based V8's and pay particular attention to base oil Groups, it might explain a few things.

There might be something here http://www.aulro.com/afvb/good-oil/7...tml#post898047 but you'll have to wade through a lot of stuff.

Most 'Synthetic' oils these days are Group III based, which means they are Hydrocracked (Chevron method) or 'Slack Wax' (Shell XHVI) derived mineral oils that are highly refined.

They are no more likely to induce leaks as a predominantly Group II/II+ mineral oil with a high detergency/dispercency add package.

The same goes for PAO/ester brews, as the seal shrinkage of the PAO's and seal swell of esters is balanced in the blending, but as they are generally premium oils will have a good detergency package for their often extended service life.

For me it's normally Valvoline 15w40 synthetic blend. I usually try to find it on special so buy 20 or so litres at a time. Standard oil filter gets changed every 4-6 months along with the oil.

Gary

Originally Posted by rick130

Err, no.


Please have a read here Oil Type You Guys Use? - Defender Forum - LR4x4 - The Land Rover Forum and here Oil Type You Guys Use? - Page 2 - Defender Forum - LR4x4 - The Land Rover Forum on oil characteristics I believe are suitable for the Rover based V8's and pay particular attention to base oil Groups, it might explain a few things.

There might be something here http://www.aulro.com/afvb/good-oil/7...tml#post898047 but you'll have to wade through a lot of stuff.

Most 'Synthetic' oils these days are Group III based, which means they are Hydrocracked (Chevron method) or 'Slack Wax' (Shell XHVI) derived mineral oils that are highly refined.

They are no more likely to induce leaks as a predominantly Group II/II+ mineral oil with a high detergency/dispercency add package.

The same goes for PAO/ester brews, as the seal shrinkage of the PAO's and seal swell of esters is balanced in the blending, but as they are generally premium oils will have a good detergency package for their often extended service life.

Yeah had read of this Long, Long, Long, and longer thread which goes into great details on racing engines and the different grades of oils etc. etc. etc. all of which is information from a friend of his that supposedly works at an oil blending company. Unfortunately it still doesn' really explain ( in lament terms anyway!) good and bad in changing oils in engines that have run for an extensive time on mineral then making the sudden change to synthetic, so i'm still not conviced. Not saying what he says isn't true, but it gets very scientific.

However i have found this which explains things more simply. When to Switch to a Synthetic Oil

Just let me be clear on this. I'm not saying synthetic oils are a bad thing at all, just a little caution needs to be adhered to, and a gradual change overtime should be practised.

Apart from seals etc, an issue for old "flat tappet" design engines is the intended rotation of lifters and push rods as they "reciprocate". Full synthetic oils have additive packages to provide very low friction coefficients which is excellent for more modern, fine tolerance, roller rocker engines and the never ending quest for efficient power delivery. The reality is that flat tappet engines run "better" in terms of mechanical longevity on good quality mineral oils or if you must, semi-synthetic blends because the super- dooper full synthetic products can be a tad too slippery and therefore the induced rotation required to reduce wear is diminished. This can lead to premature wear on lifter especially between the cam lobe and lifter base. I suspect I may get burned in some quarters for these comments... so be it

Originally Posted by Hoges

Apart from seals etc, an issue for old "flat tappet" design engines is the intended rotation of lifters and push rods as they "reciprocate". Full synthetic oils have additive packages to provide very low friction coefficients which is excellent for more modern, fine tolerance, roller rocker engines and the never ending quest for efficient power delivery. The reality is that flat tappet engines run "better" in terms of mechanical longevity on good quality mineral oils or if you must, semi-synthetic blends because the super- dooper full synthetic products can be a tad too slippery and therefore the induced rotation required to reduce wear is diminished. This can lead to premature wear on lifter especially between the cam lobe and lifter base. I suspect I may get burned in some quarters for these comments... so be it

Are you talking about ZDDP?

Havn't though about how much they turn in regards to wear. At idle they turn around once every two seconds (ish).

Originally Posted by redandy3575

Yeah had read of this Long, Long, Long, and longer thread which goes into great details on racing engines and the different grades of oils etc. etc. etc. all of which is information from a friend of his that supposedly works at an oil blending company. Unfortunately it still doesn' really explain ( in lament terms anyway!) good and bad in changing oils in engines that have run for an extensive time on mineral then making the sudden change to synthetic, so i'm still not conviced. Not saying what he says isn't true, but it gets very scientific.

However i have found this which explains things more simply. When to Switch to a Synthetic Oil

Just let me be clear on this. I'm not saying synthetic oils are a bad thing at all, just a little caution needs to be adhered to, and a gradual change overtime should be practised.

That last link is incredibly oversimplified, and in the case of most syn oils not true, as I stated most these days are Group III base, and in the case of most Mobil 1 brews (PAO base) Mobil use alkylated napthalenes and not esters to balance the PAO, and a number of PAO brews still use mineral oil or Group III oils as the additive carrier solvent anyway.

In the LR4x4 thread I explain what the differences are in base oils which is why I linked to it, just couldn't be arsed retyping it all.

It's so much more involved than base oils, and the majority of oils these days are semi-syn mixes anyway, just to meet the demands of modern engines.

Originally Posted by Hoges

Apart from seals etc, an issue for old "flat tappet" design engines is the intended rotation of lifters and push rods as they "reciprocate". Full synthetic oils have additive packages to provide very low friction coefficients which is excellent for more modern, fine tolerance, roller rocker engines and the never ending quest for efficient power delivery. The reality is that flat tappet engines run "better" in terms of mechanical longevity on good quality mineral oils or if you must, semi-synthetic blends because the super- dooper full synthetic products can be a tad too slippery and therefore the induced rotation required to reduce wear is diminished. This can lead to premature wear on lifter especially between the cam lobe and lifter base. I suspect I may get burned in some quarters for these comments... so be it

Absolute, total hogwash !

The problem is that most modern oils don't have the EP compounds like the above mentioned ZDDP in the levels needed for flat tappet engines as they really aren't needed in roller follower engines, it has nothing to do with 'slipperiness'.

Good rule of thumb, don't use an ILSAC GF-4/5 spec oil in a flat tappet engine, their HTHS number is too low. (High Temp, High Shear number, the actual kinematic oil viscosity @ 150*c)
These are generally labelled as 'fuel economy' oils.
You'll need an oil with an HTHS number above 3, and above 3.5 is even better.

The other factor, which I discovered years ago building flat tappet race engines, is that lifter/follower QC has been sorely lacking for the last twenty years.
Followers aren't always radiused properly to allow correct follower rotation, and sometimes cam lobes aren't tapered properly to allow the follower to rotate !