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Modding Your Car? Oil Advice!


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30 replies to this topic

#1
oilman

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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

#2
matty_gti

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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:

#3
Rippthrough

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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

#4
johnnie

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

#5
RINRIN

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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

#6
Ludi

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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.

#7
oilman

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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....-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.

#8
Ludi

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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....-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. :)

#9
opticaltrigger

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

#10
Baz

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

#11
Galifrey

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http://www.carbibles...eoil_bible.html

Another good article on oil

#12
SurGie

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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 :)

#13
CaptainK

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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.

#14
Jarrus

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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

#15
oilman

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Any advice needed??

Feel free to ask.

Cheers

Guy

#16
Smudgey1985

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Ive been using 10w40 and havent had a problem

#17
oilman

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

#18
quat-fro

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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!!

#19
shaundean

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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

#20
SurGie

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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.