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#1 (permalink) |
Cool Scooby
Join Date: Nov 2004
Location: South West
Posts: 382
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Oil advice for modifiers
If you are modding your car and adding BHP or using it off road 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. 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 Guy |
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#3 (permalink) |
Dedicated Scooby
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Re: Oil advice for modifiers
Very interesting read
My oil air cooled Motor bike BMW runs a a 'modern' 20/50 BMW recomended the swap from 10 w a few years back in a service bulletin When I asked them why? they said long term test in 'real world' conditions had seen the lighter weight oil 'break down' and give some of the symptoms you mention above I have a lightly moded 98 uk turbo producing about 240 It is due for an ecutek re-map so hope to get 280 ish Im using 10w/40 at present the eng has done 76k miles and has been very well maintained with oil changes every four months (im using an oversized oil filter) Question is.... what Oil should I look at after the new power hike? grade and brand?? Any help and advice welcomed Dean Nobby Clark
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#5 (permalink) | |
Dedicated Scooby
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Re: Oil advice for modifiers
Quote:
Cheers Wayne... tis helpfull indeed Used 10/40 at present... so that's good matey 1240kg x 280 bhp and lots of twisty torque.... should be ok ![]() Power at Flywheel (BHP) : 280 Weight without Driver (KG) : 1240 Power to Weight Ratio (BHP Per Ton) : 229.43 0 - 60 (Secs) : 4.43 0 - 100 (Secs) : 11.89 60 - 100 (Secs) : 7.46 Quarter Mile (Secs) : 13.15 Terminal Speed (MPH) : 105.18 Drag Strip Quarter Mile (Secs) : 12.75 Drag Strip Terminal Speed (MPH) : 108.64 Thinking of replacing rad with aluminium unit... save more weight ![]()
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Poor but happy! Last edited by nobby248; 07 Jul 2009 at 10:51 AM. Reason: added info |
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#6 (permalink) | |
Cool Scooby
Join Date: Nov 2004
Location: South West
Posts: 382
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Re: Oil advice for modifiers
Quote:
A 5w-40 or 10w-40 synthetic is ideal for all year round use. Ester based are the very best, have a look at these Opie Oils - Ester Synthetic Cheers Guy |
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#7 (permalink) | |
Dedicated Scooby
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Re: Oil advice for modifiers
Quote:
Will check them out ![]()
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#11 (permalink) |
Dedicated Scooby
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Re: Oil advice for modifiers
Having read between the lines... I think they just add a PTFE type substance to thiere oils....
SLICK 50? or the like Not sure about PTFE use... heard some stories that worry me Prolong.... certainly have some big claims on thier web site Life time eng warranty only applies to cars under ten years old and under 100k But lots of small print Jury is out on this product until I find out more In the mean time I will continue to use a good quality 10w/40 Any info on SLICK 50 Use in Subaru's?
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#13 (permalink) |
Regular Scooby
Join Date: Nov 2008
Location: Coventry
Posts: 141
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Re: Oil advice for modifiers
I have heard good things to about prolong products,and if you check out Total impreza from a few months ago,the green scooby that they restore gets the full prolong treatment and gets good reports.I have ordered some engine tretment and gearbox treatment today. will post the results after i have had it in the car for 6 months.
On the subject of slick 50 i have used this in at least 20 of my previous motors and never had any problems,and i am sure it saved the heads on my MG montego turbo 15 years ago when i had to drive 7 miles off the motorway to get to a garage as the car had run out of oil.
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#14 (permalink) |
Regular Scooby
Join Date: Nov 2008
Location: Coventry
Posts: 141
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Re: Oil advice for modifiers
I must admit though ,after scouring the internet and reading various reports i have not added any to my impreza,but my legacy gt got 2 x 750 ml top ups in 3 years,and is still up and running as sweet as ever.
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#15 (permalink) | |
Veteran Scooby
Join Date: Aug 2006
Location: Sussex
Posts: 3,335
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Re: Oil advice for modifiers
The 'active' ingredient in that stuff seems to be Teflon
![]() This seems to sum up most of what I have read about this stuff pretty well; Quote:
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