what oil in a race rover v8

[v8 jago]

Now i am a little confused in what oil to put in it ! My old engine i used valvoline racing oil which used to work well it was a 20-50 without detergent in. valvoline have stopped making that and now brought a 10-60 semi synthetic out to replace it. The only problem is real steel and other places that deal in rover v8 say dont use semi synthetic or even fully synthetic. The oil wants to be about 20-50 as rovers dont have a very good oil pressure and any less than 20 is maybe to thin. I change my oil 2 or three times over the summer time and only cover approx 1000 miles in that time.

[Boosted LS1]

Go for a true synthetic if possible and stick with 20/50. I used kendall and got it from QED iirc.

I've also used a good 20/50 from a ford dealership which carried a high API rating.

Boosted.

[stevieturbo]

I used Motul 300v Competition 15/50 Synthetic in my last 4.6 RV8 twin turbo for about 18 months.
When I took it apart because it melted a piston, everything was like new inside.

To randomly say not to use synthetic is just daft.

[v8 jago]

Oils are a funny thing. Get them wrong and your pride and joy will go bang. Ive got a 15/40 to use for tommorow but i will be keeping an eye on my pressure guage and if it drops or the light comes on it will be getting drained out and something a bit thicker. i had already bought this and left it to late to get out else but im not too keen on using this one.

[randtis]

v8 jago said:

The oil wants to be about 20-50 as rovers dont have a very good oil pressure and any less than 20 is maybe to thin.

'Fraid I can't be of any help really, but I've a question nonetheless; something I've never quite understood or been able to get a firm answer to.

How can a 20W be too thin? If a 50 weight oil is of a suitable viscosity when hot, then presumably this is the viscosity the engine likes to work at; so in theory you want an oil that is as thin when cold as hot? A 20W oil will be much thicker when cold than a 50 when hot (if you see what I mean ) so an oil that has a lower 'W' value as possible should be used. Something like a fully synthetic 0W-50?

Maybe I'm forgetting something really simple, but I can't work it out. Made a bit of a hash out of explaining what I mean though didn't I?

Cheers

Edit: and have fun tommorow

>> Edited by randtis on Saturday 18th June 15:13

[stevieturbo]

I would never use a 0 weight oil in any engine. But thats just me.

[randtis]

stevieturbo said:

I would never use a 0 weight oil in any engine. But thats just me.

Why? I can't understand any reason why not; surely something like an Ester based fully synthetic 0W-50 would be perfect in the engine above? Except for the need for more VI Improvers over say a 20W-50, but is that really a big problem if the oil is fully synthetic?

Cheers

[stevieturbo]

Its way too thin.

Maybe a simplistic approach, and the oils film strength should be good, but I still wouldnt use it.

I know of a few Subaru engines that have died within a few hundred miles of using 0-40 oils.
Occasionally big ends are a problem with Subarus, but uaing crap oil doesnt help.

I always use either Mobil 1 motorsport 15/50, or the Motul as previosly mentioned, and have never had a problem.

Any possibly power gains from running a thin oil, are absolutely minute, compared to the risks they could pose to an engine.

I put about 450-500 bhp through my RV8 for well over a year. As I said, all bearings etc were like brand new when I took it apart.
It worked for me...How many other people are pushing that sort of power in an RV8 ? Admittedly I still had a 6krpm max though.

[randtis]

stevieturbo said:

Its way too thin. Maybe a simplistic approach, and the oils film strength should be good, but I still wouldnt use it. I know of a few Subaru engines that have died within a few hundred miles of using 0-40 oils. Occasionally big ends are a problem with Subarus, but uaing crap oil doesnt help. I always use either Mobil 1 motorsport 15/50, or the Motul as previosly mentioned, and have never had a problem. Any possibly power gains from running a thin oil, are absolutely minute, compared to the risks they could pose to an engine. I put about 450-500 bhp through my RV8 for well over a year. As I said, all bearings etc were like brand new when I took it apart. It worked for me...How many other people are pushing that sort of power in an RV8 ? Admittedly I still had a 6krpm max though.

Thanks for the reply! But...

I still cannot comprehend how the 0W oil is too thin, unless you are talking about characteristics other than, yet related to, viscosity.

You mention that 0W-40 oils cause Subaru's problems; based on what I have understood I cannot see how this is a fault of the oil being too thin (assuming 40 is the recommened viscosity when hot) because the oil when cold is still waaay thicker than the oil when hot.

To my mind, the only important number is the 'hot' viscosity rating; the oil needs to be the correct grade for the engine when at operating temperature. However, I cannot see why anyone would not choose a 0W oil (or lower) to ensure (relatively) fast oil circulation at startup.

Cheers

[Boosted LS1]

Rovers are older technology (big clearances)and in those days they used thick oils. You're asking for trouble if you use a thin oil. I always stuck with 20/50, anything thinner made the thing rattle when hot. It especially hated mobile 1!

[randtis]

But surely a 0W-50 isn't ever going to be thinner than a 20W-50 would be at operating temperature? Therefore it is never too thin?

For instance, a -40W-50 (don't know if such a thing exists) will never be thinner than a 50 weight oil at operating temperature.

Cheers

[GreenV8S]

Opie Oil Man posted an article that explained this from the chemical point of view. As far as I could understand, the wider apart the 'multi' grades were, the more extreme measures were required to achieve them (he used words like 'Viscosity Improvers' too), and these measures compromise the performance of the oil. It may achieve the viscosity scores, but there are other things to worry about too.

[randtis]

Thanks, I thought there must have been another reason why oils with a low 'W' (and large difference between hot and cold viscosity rating) rating were not always recommended; guess this is one for the oil engineers to worry about!

However, if you change the oil regularly I would expect that there is not sufficient time for the oil to go out of grade and therefore an oil that provides maximum cold start protection (by being relatively thin) and is relatively thick when at operating temperature will be advantageous.

Cheers

[stevieturbo]

ok, use a 0 grade....

If it burns loads of oil and finally starts knocking, we can all have a laugh

It might not happen, but I wouldnt be chancing it.

[randtis]

stevieturbo said:

ok, use a 0 grade.... If it burns loads of oil and finally starts knocking, we can all have a laugh It might not happen, but I wouldnt be chancing it.

I cannot see any reason why a 0W weight oil is any more likely to cause a problem over a 20W oil, assuming it is not used over an extended period of time (like ten thousand miles); in this instance it will be drained regularly and therefore surely there is not sufficient time for the oil to 'shear down'?

Can the engine failures you mention definitely be attributed to the use of a 0W oil? And after what mileage was the oil changed?

I am not questioning your judgement simply trying to ascertain why.

Cheers

[stevieturbo]

Not definately no, but I would be sure they speeded up the process.

I wouldnt risk any engine with an oil I wasnt 100% happy with. Ive reccomended what I know worked for me, and under relatively harsh usage.

[MGBV8]

Motul 300V
............................ 5W-40 .... 10W-40
Viscosity at 40 C ...... 80,8 ........ 89,5
Viscosity at 100 C .... 13,8 ........ 14.0
HT/HS .................... 4,51 ........ 4,19

Large clearances means the oil system leaks more and gives a low pressure but flow is fine so not an issue.

Engine metals expand and contract with heat so clearances change as engine warms, however bearing clearances should be tighter than when warm. From above the oil is the opposite. To enable oil to flow at low temps and provide protection as soon as possible it needs to be thin so 0W40 is standard fill with Porsche.

Minerals have a problem as to use a thin base oil say 20wt viscosity improvers have to be added to make it 50wt when warm. These are long chain polymers and shear and also temporary shear(at the bearing they will line up and viscosity is reduced).

Synthetics naturally flow when cold so do not really need these vis. improvers.

The important number above is HTHS (this is viscosity at 150c normal bearing temp) the higher the better and although in general higher viscosity gives higher HTHS it also depends on base oil.

M1 0W40 HTHS 3.6
Redline 5W20 3.3
Castrol 10W60 3.6

High viscosity oil sap engine power and generate heat, so its better to use thinner oil but with a high HTHS. Unfortunately the performance component are ester which are expensive. Redline and Motul are high ester based oils

[55jnj]

Did an oil change on my 4.5 Chim yesterday (2,000 miles snce last) & used Helix Fully synthetic 5W-40. Any views ?

>> Edited by 55jnj on Sunday 19th June 13:18

[MGBV8]

Shell Helix Ultra = XHVI/PAO blend
They have an extended range

www.autosport-international.com/shownews-17.asp

[stevieturbo]

With regards to the high viscosity oils sap power...

I read a report recently on an LS1, where they dynoed a new LS6 crate motor in the US.

After trying various bolt ons, they decided to change then oil for a thin oil, 0 weight as opposed to teh 10 or 15 they had been using.. Cant remember the exact grade.

Power gains were virtually nothing, and even the dyno operator ( one Mr D Vizard ) said that using the thinner oil probably wasnt worth it in the interests of engine longevity.