5w50 oil

[ph1l5]

Is millers 5w50 oil safe to use on a 94 4.0 that has 90,000 miles on and gets driven enthusiastically ?

[selnic]

In a word NO, 5/50 is very thin and will make it rattle like a bd, always use 15/50 silkoline in mine.
HTH

[dog man]

5/50 would be suited to a really cold climate where the ambient temperature is down at -30 or whatever but where you also need high temp viscosity. As we're not usually faced with such low temperature cold start situations the 5/50 would possibly lead to clattering lifters on start up.

[JonathanT]

I presume that 5w50 and 15w50 should have similar performance/characteristics at temperature?

[Chimpafrolic]

In my opinion the RV8 (especially if its done over 50,000 miles) favours a heavier semi synthetic oil.

Buying a good quality oil and changing it regularly is equally important.

Everyone seems to have their favourites but here are my two preferred oils:

1) Millers CSS 20w60

2) Penrite HPR 15W-60

A reliable source for the Millers CSS 20w60 at a good price is:

http://www.fluidsinmotorsport.co.uk/twenty50.html?...

Both the above oils contain Zinc which is essential in a flat tappet engine.

Many oil companies have deleted Zinc on environmental grounds, but Zinc remains the ultimate proven anti wear additive.

With RV8 cam wear a common problem, personally I would never run my engine on an oil without Zinc.

I change the oil every 3,000 miles using a decent quality oil filter, either a genuine Land Rover part, or one from Coppers or Fram.

[SMB]

selnic said:

In a word NO, 5/50 is very thin and will make it rattle like a bd, always use 15/50 silkoline in mine.
HTH

So I have never understood why people say this.

Oil viscosity is measured in 2 ways, cold ( the first figure ) and hot ( the second). Running a 20W50 oil means cold start oil is thicker and takes longer to get round the engine to protect it. The 50 determines it's hot (100 degree C) viscosity, and thicker is indeed better.

So a 5w50 or even a 0w50 is fine. Oil is always thicker when cold than hot, and you need both cold start quick protection and hot running protection.

At cold start time you need an oil to be thin, so a 15/50 and a 5/50 will give the same protection when hot but the 5/50 will be better when cold.

[SILICONEKID340HP]

The engine design is over 50 years old and ran very well on 20w50 so i use mineral valvoline vr 1 racing oil.people say it can sludge up but if your not doing high mileage its not a problem..I may move to millers 20w60 semi synthetic at a later date.. Some of the guys on here have complained of very noisy engines after paying a fortune at TVR service centres ...with very thin oil.

Edited by SILICONEKID340HP on Friday 27th May 19:08

[SMB]

SILICONEKID340HP said:

The engine design is over 50 years old and ran very well on 20w50 so i use mineral valvoline vr 1 racing oil.people say it can sludge up but if your not doing high mileage its not a problem..I may move to millers 20w60 semi synthetic at a later date.. Some of the guys on here have complained of very noisy engines after paying a fortune at TVR service centres ...with very thin oil.

Edited by SILICONEKID340HP on Friday 27th May 19:08

So I can see that with 0w40 oil, but it's the 40 thats the issue not the 0. The 0 is still thicker than the 40 bit... so any tapping will be when it's hot.

[dog man]

The first number refers to the performance of the oil at a given ambient temperature while the second is a measure of how hot it can get and still retain it's viscosity.

Seeing as 5/50 was the op, the first ''5'' denotes that it will work down to something like -30 i.e it will not freeze. So if you run this oil in 'normal' ambient temperatures that we have here the result is that it will initially (start up) be thin. In a push-rod V8 this might cause the lifters to chatter maybe, whereas I think some more modern engines are designed for this oil.

''W'' stands for 'winter' and 10/40 seems the best all round viscosity for this country. Beyond that it's how hot the engine gets hence say using Mobil1 Motorsport 15/50 in a high performance car that is driven hard on track or whatever.

All you're doing by using 20/60, 15/50, 10/40 etc etc etc is getting different minimum and maximum viscosity performance.

[selnic]

Well explained Dog Man, hope that helps the OP and those who suffer from the hard of understanding.

[chris2002hk]

Why would you choose an oil based on 50 year old chemistry? Oils have evolved so much that any engine following correct service interval changes, will last significantly longer and maintain working tolerances than using 1970 castrol. Remember that veggie oil the racers used to use to get over limited tolerances?
A regular change is still the main way to prevent wear , hence the need for a full car history. Little point in using fully synthetic oil that costs a bomb, if previous owner ran car on the same black gunk for last 30k miles!