Oil advice and recommendations here

[oilman]

According to my database all Saxos from the 1.0 to the 1.6VTS show either 10w-40 or 5w-40 as the recomended engine oil.

So what the whole oil debate here boils down to is not what grade to use, you have a choice it's 5w-40 or 10w-40.

The questions are

What quality do you need

What are the differences between 10w-40 and 5w-40

What are the benefits/downsides of using 10w-40 or 5w-40

Many car owners unwittingly change the OEM oil recommendation by modding their car or using it on track. These factors influence firstly the quality of oil you use and in extreme situations where cars have been heavily modded (generating more heat within the engine) sometimes the viscosity required.

I have a lot of articles on this stuff, some written bu me and some by chemists and technical bods that I have day to day dealings with.

I will post these up over the coming days as questions arise but here is one that will be of interest.

Cheers
Simon

[oilman]

Originally Posted by cammedvtr

i just use normal oil from my local motor factor (to citreons hand books spec), i have 93000 miles on the clock and its never missed a beat and she slighty modded. Ive had her since she had 35000 mine on the clock and my bro did the serives on her after the warranty ran out because the car belonged to his mate. i work on the theary(sp)avarage quality oil and 3000 miles changes. but every ones differnet.

Indeed there are different schools of thought about cheap oils changed regularly but there are no real factual arguments, here is my opinion.

Cheaper oils are in the long run a false economy, In the first mile the higher volatility, inferior anti-wear performance and poor temperature resistance of a cheap grade of oil will start to show. Obviously, there will be no immediate effects. The whole point of top quality oil is long-term performance retention, which is particularly valuable to people who actually own the car they drive. The ‘performance’ enthusiast will want to retain the new-spec BHP figures, and the cost-conscious will want to see good fuel economy with 100,000 on the clock.

Cheap oil, (particularly 10W/40 or thinner) evaporates quickly, and the vapour is drawn into the combustion chambers via the crankcase ventilation system. This means calcium and zinc oxide deposits (from oil additives) which will cause pre-ignition, so the knock sensor retards the ignition, giving less power and poor fuel economy. The deposits also contaminate the exhaust catalyst, leading to high emissions and MOT failure. How much does an average catalyst box cost these days?!

In most cases synthetic oils (proper ones that is) are the way to go if you intend to keep the car or the car is somewhat special or used hard.

Cheers
Simon

[oilman]

If you are "modding" your car and adding BHP then consider your oil choice carefully as the stock manufacturers recommended oil will not give you the protection that your engine requires.

A standard oil will not be thermally stable enough to cope with higher temperatures without "shearing" meaning that the oil will not give the same protection after a couple of thousand miles as it it when it was new.

Let’s start with the fundamentals. An engine is a device for converting fuel into motive power. Car enthusiasts get so deep into the details they lose sight of this!

To get more power, an engine must be modified such that it converts more fuel per minute into power than it did in standard form. To produce 6.6 million foot-pounds per minute of power (ie 200 BHP) a modern engine will burn about 0.5 litres of fuel per minute.(Equivalent to 18mpg at 120mph). So, to increase this output to 300BHP or 9.9 million foot-pounds per minute it must be modified to burn (in theory) 0.75 litres.
However, fuel efficiency often goes out of the window when power is the only consideration, so the true fuel burn will be rather more than 0.75 litres/min.

That’s the fundamental point, here’s the fundamental problem:

Less than 30% of the fuel (assuming it’s petrol) is converted to all those foot-pounds. The rest is thrown away as waste heat. True, most of it goes down the exhaust, but over 10% has to be eliminated from the engine internals, and the first line of defence is the oil.

More power means a bigger heat elimination problem. Every component runs hotter; For instance, piston crowns and rings will be running at 280-300C instead of a more normal 240-260C, so it is essential that the oil films on cylinder walls provide an efficient heat path to the block casting, and finally to the coolant.

Any breakdown or carbonisation of the oil will restrict the heat transfer area, leading to serious overheating.

A modern synthetic lubricant based on true temperature-resistant synthetics is essential for long-term reliability. At 250C+, a mineral or hydrocracked mineral oil, particularly a 5W/X or 10W/X grade, is surprisingly volatile, and an oil film around this temperature will be severely depleted by evaporation loss.

Back in the 1970s the solution was to use a thick oil, typically 20W/50; in the late 1980s even 10W/60 grades were used. But in modern very high RPM engines with efficient high-delivery oil pumps thick oils waste power, and impede heat transfer in some situations.

A light viscosity good synthetic formulated for severe competition use is the logical and intelligent choice for the 21st century.

Cheers
Simon

[citroenaxgtr]

Originally Posted by oilman

This has the 1.6vtr Saxo engine in an ax, correct?

What do you use it for road/track etc?

Cheers
Simon

near enough correct yes!.. but not using injection!.
im using the head from an ax gt along with the carburettor!. i do intend to use on roads and track!.

[oilman]

Originally Posted by citroenaxgtr

near enough correct yes!.. but not using injection!.
im using the head from an ax gt along with the carburettor!. i do intend to use on roads and track!.

Interesting! Do you know if this has had any effect on the normal and maximum oil temps or do you not have an oil temp gauge?

Cheers
Simon

[citroenaxgtr]

the engine is yet to be put into the car!. i have to make the loom to make this work!.. shouldnt be long now i have the loom worked out. im just waiting for a hoist now to lift the engine in!.

[oilman]

Is it rebuilt then and not run in?

Cheers
Simon

[citroenaxgtr]

no the engine has done about 50k not sure of the head!.

[oilman]

I would look at a good 5w-40 synthetic as it will be used in anger on the track... look at Silkolene, Motul, Amsoil and fuchs.

Cheers

Simon.

[citroenaxgtr]

cheers!

[vtrchris64]

Saxo Vtr 1.6 8v
80k miles
Mainly short journeys, driven hard now and then.
Just put 10w-40 gtx Magnatec in would this be ok?

[oilman]

For a stock road car yes it will be fine, you will get more protection from a fully synthetic but you'd need to weigh up the costs.

Cheers
Simon

[VTaaRon]

Originally Posted by oilman

What viscosity (grade) oil are you using at the moment as it could account for poor cold start.

Cheers
Simon

check here mate my saxos tipple!

[WestyVTR]

i use 10w-40 GTX magnitec, but i did use 15w-40 between 70-85k. Shes sitting pretty wiv 108.5k on the clock now. She used to have a 106 rallye box in her witch ment at 60mph the revs were rather high!! also has a full exhaust no cat & an air filter, and i change the oil&filter as often as possible.... Hell i even replace things sumtimes that dont really need it, but its all relivant.

recomended oil i guess is a 5w-40 but i always let her warm up before i drive her anyway so is there much difference? 10% of engine wear occuring in the first 10-15 mins but shes stood still anyways!!

[oilman]

Originally Posted by VTaaRon

check here mate my saxos tipple!

I can't read form the picture whether this is a 15w or 10w oil but you'll get better cold start from a 5w-40.

Before you ask, no it's not too thin!

Cheers
Simon

[oilman]

Originally Posted by WestyVTR

i use 10w-40 GTX magnitec, but i did use 15w-40 between 70-85k. Shes sitting pretty wiv 108.5k on the clock now. She used to have a 106 rallye box in her witch ment at 60mph the revs were rather high!! also has a full exhaust no cat & an air filter, and i change the oil&filter as often as possible.... Hell i even replace things sumtimes that dont really need it, but its all relivant.

recomended oil i guess is a 5w-40 but i always let her warm up before i drive her anyway so is there much difference? 10% of engine wear occuring in the first 10-15 mins but shes stood still anyways!!

Engine wear at cold start is 90% not 10% and yes 5w-40 is better for cold start than 10w or 15w etc

Cheers
Simon

[cammedvtr]

Nissan Skyline 2.6 Twin Turbo GTR
Import) 1997
42,000 (miles) on the clock

Full HKS Race Exhaust
Turbo Hard Pipe Kit
Twin HKS Super Plower Flow Fiters
ECU Remap
Enlarged Intercooler
Enlarger Oil Cooler

Normal Sunday Driving and a few quarter mile days.

[oilman]

If you frequent the skyline forums, you will see that many owners use Silkolene Pro S 10w-50 or Pro R 15w-50 on our advice and love it.

It's what I'd recommend

Cheers
Simon

[Simop]

Simon, thanks for all of the great advice!

For my sins, Im a chemical engineer by trade and qualified chemist, so all of the technical info is greatly appreciated. From my point of view - keep it coming!

Regarding my oil requirements...

The car in question is a Saxo VTS, which has been turbocharged. bhp ~ 240bhp @ fly.

The car has been mothballed since December and will be back on the road in the coming weeks, ready for a year of track action. (its my 2nd car)

So, baring in mind the extra abuse and higher oil temps the turbo is likely to generate, what oil would you recommend?

I have a large'ish oil cooler fitted, with no secondary thermostat, so on cold startup, the oil is constantly cooling.

One observation... For a number of years I used Mobil 1 oil, however I observed that the oil tended to seep past the camshaft oil seals?

Now this could have been a seal problem, but I put it down to the low viscosity oil and stopped using it... the problem went away? It was never a large leakage, more of an annoying drip that occasionally needed to be wiped from the camshaft cover joint.

I look forward to your recommendations.

[oilman]

Simo,

Oil temps are the key here, it is common for people who turbo normally na engines to use a thick oil, thinking that it will require it, this is not always true.

If the oil temps remain below 120degc then you are looking at a 5w-40 full synthetic for all year round and track use, I would have thought this would be the way to go as you have a large oil cooler, using a thick oil thats running too low temps is as bad a running a thin oil at temps too high.

If however the temps rise above this then we would suggest a 10w-50 full synthetic.

Have a look at Motul, Silkolene and Amsoil.

Cheers

Simon.