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Discussion Starter #1
Last evening whilst drinking quite heavily with a couple of friends, the subject of Oil changes came up.

I am a 'heretic' in this matter saying that it ain't the Oil that should be changed so often as the Filter.

Since the introduction of Synthetic Oils I have always used the following 'method' to determine my Oil changes;

I change the Oil when the car has acrued 150 'demerit' points and the filter after 150 'starts' that is it 150 starts and the filter is thrown away and its 'half pint of oil in it.

Demerit points;
First start after leaving overnight= ½ point
Any other start= 1/4 point
1 'overtemp' occurence (100C) 5 points
Prolonged 'Day long' Driving= ½ point

Mileage counts for nothing!

My filters last about 5-6 weeks and my Oil changes happen around 5000-12000 miles.

I have access to testing Equipment and even when I change over the film strength is still more than 90% of the original so I probably could comfortably go 18,000miles without trouble, this from a Twin Turbo/Twin Cam 380hp motor which will every week see 140+ a few times and 160/170 often as not, don't ask!

This led to a heated discussion about whether 3000 mile oil changes are ever needed, my contention being they are just a 'throw back' from the non-synthetic era.

What do you Guys/Gals do?
 

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My car gets the fluids changed every 6 months - regardless of mileage.

Daz
 

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Mycroft,

That is sort of what Amsoil does. They say to change the filter every 5k miles, but only change the oil every 25k miles. That's what I do.

Consumer Reports in the states did an independent test on 50 N.Y. cabs. They put 60k miles of city driving on each cab, with different intervals of oil changes, and different types of oils. After the test period, they tore down all the engines and measured for wear. Between the 3k synthetic, and a 8k conventional oil change there was no wear difference. They did say to make sure the oil you use was SAE qualified, though.

I will always run synth, since I have seen dyno run that prove the increase in HP. I run Amsoil.
 

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As a slight diversion - when changing my oil (and filter) a few weeks back the oil was horrid - dark black and only 7K miles done. I did flush the engine prior to the change but what I'm wondering is what exactly affects the colour of the oil and does it actually represent in any way it's effectivenes (or lack of)?
 

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Discussion Starter #5
Carbon products cause the 'black' it is a phallacy that it means the oil is 'dead', it can indicate this but it is not indicative of it, in fact there is a quite a good case that can be made that if the filtration is good that the carbon will assist in the lubrication, it may not help where the engine is has very high internal pressures as the carbon can cause the breakdown of the film compnent that really protects the engine at the top end of the envelope.
 

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I

Change my oil every 1000 mls and my filter every other chage, if I could post pictures i would show some bearings at 30,000 mls brand new
Gary
GT-ART OFFICIALY JAPANISE:D
 

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Iain,

Life's too short.....

Ditto Gary or even less miles depending upon when the track days come.

How does the addition of petrol affect oil? As you know, running higher boost will cause a certain amount of blow by past the pistons leading to contamination of the oil by petrol. We all know how much thinner used oil is compared with new, surely not a good thing....?

Tony,

Do you honestly not change the oil until 25k miles? :eek: This may be OK, although I can't see it, for NA cars but I can't see it for FI car...

Peter.
 

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Petrol

F**ks oil
Gary
GT-ART
OFFICIALY JAPANISE:D
 

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Discussion Starter #9
PeterE said:
Iain,

Life's too short.....

Ditto Gary or even less miles depending upon when the track days come.

How does the addition of petrol affect oil? As you know, running higher boost will cause a certain amount of blow by past the pistons leading to contamination of the oil by petrol. We all know how much thinner used oil is compared with new, surely not a good thing....?

Jon,

Do you honestly not change the oil until 25k miles? :eek: This may be OK, although I can't see it, for NA cars but I can't see it for FI car...

Peter.
For 'racing' then there is value in what you say even a very hard 'trackday' might merit a change as it is during this time that small metallic slithers can become dislodged causing trouble.

The same applies to engines with a high specific output 300bhp/ltr is a high stress motor and it would merit regular changes due to the film strength being lost fairly quickly.

Under 200hp/ltr and things are not so dramatic and Oil lasts a lot longer than we are all led to believe.

Petrol in the blowby, well even that isn't as bad as it's made out to be, a High TBN and the Oil will cope nicely thank you, the petrol is not in itself harmful, it is the byproducts of its 're-distilation' that cause corrosion problems, a high TBN and even that is knocked on the head.

What used to happen with the old organic Oils was that they were made from variable length and size molecules* the blowby would destoy the size that really mattered now when that size may have only constituted 5-10% of the oil mass this was a very bad thing, now when this size constitutes 95% of the oil mass it just doesn't matter any longer.


(*they needed this as the technology surrounding Oil was a bit 'Hit and Miss', now with Fully Synthetic we can specifiy the exact size of these components)
 

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come on

Mycroft,
allthough most of the cars or people on this forum use their cars for road use only , you aint telling me that high rpm road use is not racing ? for an engines point of veiw ?
Gary
GT-ART
OFFICIALY JAPANIESE:D
 

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Discussion Starter #11
What we are looking at here is 'duration of stress' on the road no matter how hard you try you would never be able to put a 750hp motor to full use except for maybe a fleeting moment or 2 but on a yrack you will pound that motor in a manner that is just beyond anything it will experience on the road.

So indeed from an engines perspective 9000rpm is 9000rpm no matter where it occurs, unless the engine is loaded it will just not suffer the resistive stresses that reaching 9000rpm means on the track.

Let's put this in its simpleat terms, if you took your 750hp engine and cloned it, you left one on the bench and the other stayed in the car and you 'coupled them through electronic means to each other, whatever the track car did the bench unit did, but with one crucial difference the bench engine had only half the 'loads' imposed on it but it still matched the other rev for rev.

Which engine would outlive the other?

It is an extreme extrapolation, but I think you will catch my drift.
 

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Yeah

but,
thats the problem discussing things of this nature in the pub,
respect your veiws but 1000 ml intervals for me
Gary
GT-ART
OFFICIALY JAPANIESE:D
 

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Discussion Starter #13
We only discussed 'methodology' in the pub, we did the research 'stone cold sober' in the lab.

But as I think you are alluding to, the cost of that motor of yours far outweighs the cost of changing the oil that often so for peace of mnd you will not change, and damned right my friend, damned right.

I only seek to dispel myths, it is part of my job.
 

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SURE

Thing my friend,
did you ever do any tests on the cerracote ? as a matter of interest
Gary
GT-ART
OFFICIALY JAPANIESE:D
 

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Peter,

What I should have said was, I change out my filter more often than my oil. Amsoil recomendations are for normal cars. I really don't think a GTR is a normal car:) I will probably change it out every 5k, and do like what Mycroft suggested with the filters.

I believe in Amsoil, but I am not about to wait till 25k to change it out, that would be:mad:

Tony
 

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Discussion Starter #16
Re: SURE

gary said:
Thing my friend,
did you ever do any tests on the cerracote ? as a matter of interest
Gary
GT-ART
OFFICIALY JAPANIESE:D
Yep, and it works very well.

I presume most people here have had a can off you?
 

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Oil additives

Just for the record I change the oil in all my cars every 4-5,000 miles, or every 6 months, or if I just think it looks or smells bad.

My Skyline gets a lot of above average abuse what with autobahns and the regular visits to Nuerburgring and shows no sighs of wear.

I have used a few different additives over the years the latest being Prolong, before that Duralub, and also good old Slick 50,

Mycroft,

Is there an oil additive that in your experience that really works?

Paul.

PS I've used Castrol Syntec 5W-50 almost exclusively for the past 10 years (Nissan folk here insist I use Castrol RS 10W-60 :rolleyes: ).
 

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gary said:
my filter every other change
I got flamed not so long ago for suggesting that the filter only needs changing every other time when doing regular oil changes.

Go on Gary, admit you stole my idea ;)
 

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Discussion Starter #19
Oil technology marches forward almost monthly yet filter technology hasn't really had a major leap forward since the mid 80's.

To some extent it has gone backwards as the manufacturers managed to get the only standard they ever had to 'adhere' to removed in '93, frankly I trust Oil filters about as much as I trust Politicians.
 
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