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oilman

Modding Your Car? Oil Advice!

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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 late1980s 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.

You must seriously consider a "true" synthetic for "shear stability" and the right level of protection.

 

Petroleum oils tend to have low resistance to “shearing” because petroleum oils are made with light weight basestocks to begin with, they tend to burn off easily in high temperature conditions which causes deposit formation and oil consumption.

As a result of excessive oil burning and susceptibility to shearing (as well as other factors) petroleum oils must be changed more frequently than synthetics.

True synthetic oils (PAO’s and Esters) contain basically no waxy contamination to cause crystallization and oil thickening at cold temperatures. In addition, synthetic basestocks do not thin out very much as temperatures increase. So, pour point depressants are unnecessary and higher viscosity basestock fluids can be used which will still meet the "W" requirements for pumpability.

 

Hence, little or no VI improver additive would need to be used to meet the sae 30, 40 or 50 classification while still meeting 0W or 5W requirements.

 

The end result is that very little shearing occurs within true synthetic oils because they are not "propped up" with viscosity index improvers. There simply is no place to shear back to. In fact, this is easy to prove by just comparing synthetic and petroleum oils of the same grade.

 

Of course, the obvious result is that your oil remains "in grade" for a much longer period of time for better engine protection and longer oil life.

 

If you would like advice then please feel free to ask.

 

Cheers

Simon

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matty_gti

hi, that was a good read.

 

Ive got a 1989 1.6 8v 205gti with 86k on the clock and its just had the head rebuilt. its going to get driven very hard on the road (bit of a boy racer :( ) and i want to know which is better 'semi synthetic' or 'synthetic' like maybe castrol GTX 10w-40 and what is teh best grade i.e 5w-40, 10w-40, or 10w-50????.

 

P.S, money is no matter, i just want the best :lol:

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Rippthrough
hi, that was a good read.

 

Ive got a 1989 1.6 8v 205gti with 86k on the clock and its just had the head rebuilt. its going to get driven very hard on the road (bit of a boy racer :) ) and i want to know which is better 'semi synthetic' or 'synthetic' like maybe castrol GTX 10w-40 and what is teh best grade i.e 5w-40, 10w-40, or 10w-50????.

 

P.S, money is no matter, i just want the best :P

 

 

Don't know what Simon would recommend but I'd say a 5w-40 fully synth. Personal favorite is Silkolene

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johnnie

Try Mobil 1 Fully Synthetic 0W/40. If you running more in the city then 10W/40

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RINRIN

This also depends on the condition of the engine. If you have an worn engine you need to use thicker oils.

Fully synthetic oils are newer engines.

Best is the one from the factory. :) check it and use it

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Ludi

Can somebody tell me who is the best oil for 205 1.9 gti,I`ve just re-build the engine.What do you think about Total 9000 full syn.

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oilman
Can somebody tell me who is the best oil for 205 1.9 gti,I`ve just re-build the engine.What do you think about Total 9000 full syn.

 

If it's just rebuilt, use mineral/semi-synthetic oil to run it in for the first 500 miles. After that, go to a fully synthetic 5w-40, http://www.opieoils.co.uk/c-656-5w-40.aspx.

 

The Silkolene Pro S, Motul 300V and Redline are some of the best oils available, so if you want the best, go for any of those. If you want a good, cheaper alternative, have a look at the Motul 8100 X-Cess or Fuchs Titan Supersyn.

 

I'm not familiar with the Total 9000, but i had a quick look and from what I can see, it's similar to the Motul 8100 or Fuchs Supersyn, so a good choice, but not the best available.

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Ludi
If it's just rebuilt, use mineral/semi-synthetic oil to run it in for the first 500 miles. After that, go to a fully synthetic 5w-40, http://www.opieoils.co.uk/c-656-5w-40.aspx.

 

The Silkolene Pro S, Motul 300V and Redline are some of the best oils available, so if you want the best, go for any of those. If you want a good, cheaper alternative, have a look at the Motul 8100 X-Cess or Fuchs Titan Supersyn.

 

I'm not familiar with the Total 9000, but i had a quick look and from what I can see, it's similar to the Motul 8100 or Fuchs Supersyn, so a good choice, but not the best available.

 

 

Thanks for the advice. :)

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opticaltrigger

Thanks very much Oilman.

Thats one of the most informative,direct,and learned articles on the subject I have ever read.

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Baz

I doubt it'd sell oil to the arabs though.

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SurGie
I doubt it'd sell oil to the arabs though.

 

How very droll :P

 

Thanks oilman, thats very informative.

 

Iv recently bought some Silkolene pro 10/50 for my 306 GTI6 and i got a discount being a member.

 

Cheers :)

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CaptainK
Iv recently bought some Silkolene pro 10/50 for my 306 GTI6 and i got a discount being a member.

Thats a bit thick isn't it? Or is your 306 GTi6 a dedicated track car or has it been turbo'd / SC'd where it needs the extreme high temperature protection of a ?w50 oil ? I run the Silkolene Pro S 5w40 for my cammed and ITB'd GTi6 engine and its been around Europe and done 26 laps of the Nurburgring. The 5w40 gives much better cold start viscosity to allow the oil to circulate quicker when cold.

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Jarrus

I use Castrol Edge in my dturbo, some people say it's a bit over kill for it but I've never had a bit of trouble from it so it must be good stuff,

How do you guys rate the stuff for petrol cars?

 

Brett

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oilman

Any advice needed??

 

Feel free to ask.

 

Cheers

 

Guy

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Smudgey1985

Ive been using 10w40 and havent had a problem

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oilman

A 5w-40 would give better cold start protection, but 10w-40 is a decent choice

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quat-fro

I'm surprised that Oilman hasn't been kicked out of the 205 forum - he didn't last long on the British rally forum when he started posting speculative oil advice there!!

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shaundean

I have a standard 1990 1.9 8v GTi engine. it has had the some head work done. i do a lot of driving in town and on short runs 10-20mins, i know this is bad for the engine full stop but what oil should i be using for the best protection and life between changes?

 

Thanks

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SurGie
Thats a bit thick isn't it? Or is your 306 GTi6 a dedicated track car or has it been turbo'd / SC'd where it needs the extreme high temperature protection of a ?w50 oil ? I run the Silkolene Pro S 5w40 for my cammed and ITB'd GTi6 engine and its been around Europe and done 26 laps of the Nurburgring. The 5w40 gives much better cold start viscosity to allow the oil to circulate quicker when cold.

 

 

I got that advice from the 306 forum and having it thicker will mean when engine is hot and run high revs it stays thick, it works ok for me.

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CaptainK
I got that advice from the 306 forum and having it thicker will mean when engine is hot and run high revs it stays thick, it works ok for me.

Gosh, that was nice of myself to post that on the 306 Forum. ;)B)

 

But yes, I do a lot of short journeys too and its recommended to go with a thinner "cold start" oil. Thats the number at the starts of the oil spec - e.g. a 10w40 would be a "10" when at "cold". The lower the number the easier the oil will circulate when you first start the engine, and obviously oil getting to moving bits quickly is good for the engine. The later number relates to how thick the oil is when at "running temperatures". The higher the number the thicker it is - generally for the UK climate anything higher than a "40" is to be avoided unless you regularly do track days etc as the engine temperature will be running much hotter than normal. As my quote above says I use a 5w40 oil personally. To be honest it doesn't matter an amazing amount in the UK climate as long as you have 10w40 or better, just don't rev the nuts off the engine for the first 5-10 mins of driving. :lol:

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SurGie

I see what you mean about the velocity etc but here is what it says on the back of my Silkolene 10W/50.

 

 

"It exceeds the performance requirements of many engine manufacturers. Combines exceptional anti wear performance and outstanding high temp protection with excellent cold start characteristics. Suitable for use in turbo charged and normally aspirated to ensure continued maximum fuel economy and reduced emissions"

 

 

 

This is why i bought it for my 306 gti6 as well as the recommendations.

Edited by SurGie

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CaptainK

The 10w50 will work fine if thats what you want to use. However, I still believe a "50" oil is far too thick for normal road use for a N/A engine. Turbo'd big power engines and on cars used a lot on track then yes, as engine temps would be greater then and thus you would need the viscosity of the "50" to stop it going pete-tong.

 

I used to use a "50" in my FTO (the exact Silkolene 10w50 you mention) thinking it'd be better. But manfufacturers spec for both the FTO engine and 205 engines I believe is a "40", so I started using the 5w40 especially as I sometimes did short journeys. No point going higher than that in the UK Climate as the oil will just remain a tad thicker when at engine operating temps - which actually increases fuel economy and emissions to turn the oil pump to overcome the friction of the the thicker oil being circulated around the engine.

 

Do you also plan on changing the 10w50 to something thinner for the UK winter ? The 10w50 for UK winter use in our N/A cars may be far too thick and take a fair few miles of driving to get upto correct running. Thats what concerned me most on my daily drives to work in winter - that the "50" wouldn't get up to speed very well in the cold. Also the "5w" part of it for winter use is good as it makes it "thinner" at cooler temps and thus allows the oil to more quickly circulate around the engine in the cold winters from the moment you first turn the key.

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SurGie

I'm thinking of getting some of the 10W 40 fully synthetic for the winter, my oil temp in my 306 GTi6 gets to 90 after around the 3 miles mark and does not go any lower unless its very cold outside. I always let the engine warm up well before i high rev it and i dont go over the 3 k mark until it reaches the 90 temp. Today it went to the 100 mark driving around town. My water temp is around the 90 to 110 mark around town driving and at 70/80 on longer journeys and in winter on any type of journey just about.

 

Im just worried that if the oil is too thin when high revving and in the summer months it could do some damage to the crank, this happened to my MI16 2 years ago. So do you think 10W 40 is about the best all rounder during both seasons ?

 

There's so much to think about when choosing the right oil for the right spec and use.

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CaptainK

The GTi6 gets hotter in the 306 does it ? Mine doesn't get that hot in the 205 surprisingly.

 

Anyways, if you want some examples of high revving in the summertime without any problems - my last fill of 5w40 in my 205 GTi6 included (on the same oil) :

 

1) An "interesting" 205 Eurotrip last year in May where it was rather warm and included visiting 10 countries in 10 days including deep down south down to Croatia etc where its much hotter than the UK.

2) That same oil also did 25 laps on the Nurburgring on a separate 'Ring Trip over the Easter Weekend last year..... and last year's easter weekend at the 'Ring was immensely overhot to the point my tyres were dying after 2 laps of the ring.

 

So personally for me, I think the Silkolene Pro S 5w40 has proved to me it can stand up to a lot of high revving in very hot situations. :)

 

On a more serious note, I think Peugeot's manufacturer spec is a 10w40 for the UK. So the 40 is what they are saying as well, but I just chose a 5W as it means it'll pump better around the engine from first start, especially in the cooler winters. The 10w50 will be fine as well for normal use, but on the flip side of thinking about it the extra viscosity of a 50 whilst high revvings might cause too much oil pressure to build up. Who knows really ? All I know is that my FTO ran happier when switching from 10w50 to a 5w40. I too got the 10w50 for my FTO thinking it'd be better for its high revving nature.

 

The best thing for you to do is do like I did - try out various oils and see what you like the best. :lol:

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