Has question (Oil is Motul 300v)

 

130 degrees is starting to push the limits of the oil...

 

If its getting up there then cooler is essential.

Something to consider for track, the Sti5 T R id did b4 you had a Motul cooler installed and temps never passed 90 under any circumstances during the runs.

bob

 

Motul 300V is fine at 130degC and I am informed will run for sustained periods at 150degC. The problem with running these temps is that you will need to consider shorter than normal change periods.

Agreed a cooler is a solution but remember that you will need to use a lower viscosity if you fit one. That's assuming you're using 15w-50.

Cheers
Simon

 

The oil may be happy at 130 degC, but I doubt the engine will be happy at whatever temp that equates to

 

In parts probably 300degC!

 

I dont like / want my oil above 105 / 110 degrees.. Im about to fit my oil cooler too.

 

im considering fitting one too especially as im going to the ring in june so may well be hot weather too....

just out of interest how do u convert degrees centigrade to degrees fahrenheit???

 

Tf=(9/5)*Tc+32

 

or in english

TF=((TC*9)/5)+32

AFAIK its correct, Im reading these out of programs I wrote a few years ago and cant really remember!

 

oilman,

surely the weight of oil should be the same even when fitting an oil cooler.

if track use dictates that you need a cooler to bring temps down to what they were before, then surely once they have been reduced by the oil cooler you want the same rating of oil as you had before you needed an oil cooler.

 

If you fit an oil cooler try to get an oil stat to control the point at which you cool the oil...under normal conditions you want the oil to warm up quickly...fitting a cooler with no stat can lead to lower temps for longer than you might want...due to the larger volume in circulation and the fact that the cooling action will be going on all the time...

 

Lol at Simon again, I used to run oil at 140 deg C quite happily on Cav turbo and it was 0-40 Mobil but I would'nt think of trying it on an Impreza engine, it would big end for certain. Why on earth would you use a cooler to keep temps down then simulate the heating effect by running thinner oil?

bob

 

I'm not sure what's funny.

The Kawasaki GP bikes that Silkolene sponsor needed an oil cooler in the Quatar GP. With air temps at 45C, the oil was reaching 170C! Over here in Europe, there isn’t much point in oil coolers when modern engines can keep a good oil pressure with thin oil.

With some classic engines, such as BMC A and B, the oil pumps are struggling when the oil viscosity drops below about 15cSt, so they do need a cooler if pushed.

Over-cooled oil can be a hazard due to Air retention/cavitation etc.

This is fact not fiction. Perhaps I just missed the joke!

Cheers
Simon

 

My Alarm was set at 120 degrees R.B. Any more than that on a subara engine is pushing your luck IMHO. At stock power levels (upto circa 300BHP) the standard modine cooler is adequate on all but the hottest of days on track, the impreza oil cooling/water cooling system is excellent compared to some other cars.

If you notice your temps getting close to 120 then drop your gear shift point 500rpm, it makes a significant diference. I always kept the length of time out on track to sensible amounts as the Impreza suffers from a gradual heat soak build up in the engine block and engine bay, sustained running jacks up the core temperatures over a 15 minute period even with good oil/water cooling.

If you are running over circa 300BHP on track then its worth installing a cooler if you intend to run for long periods at full power, if you are doing short runs its less of a requirement, even at high BHP levels, although a cooler running water stat seems to help temperatures stay under control with big power short runs on track.

Oils being used in this environment need to be carefully chosen, a 5W-30 wont do the job. Motul 300V 15W-50 or Castrol RS 10W-60 are excellent choices in my experience.

 

Simon I'm sure you didn't ... this car is not std, it has an uprated engine and is dedicated to the track ... dealer logic doesn't apply here, nor to most of the other current threads about oil if uprated spec cars are involved. Subaru quote the 5w-? is not suitable for "heavy use", anything uprated from std means that imho.

Motorcycle oil technology is totaly different.

bob

 

Agree with John about temps...you can easily see temps of 110-115 on the road with a series of point and squirt blasts ...anywhere where engine load is great and relative speed is low can be a problem as there is less relative cooling leading to heat soak...this is obviously a problem on track, but some are worse than others due to their layout...my alarm is set to 115 so that I'm alerted to keep an eye on things...and watch the oil pressure too...around 115-120 some oils will fall off quite quickly...
Temps are only useful for comparison if measured in the same place ... mine are using Defi gauges measured above no3...totally different from sump temps....

 

My defi`s read around 120 today but got to 126 at one point then i slowed the car down for a while so i think i might get on.

The car is around 400 bhp

R.B

 

Bob,

What 5w oil is not suitable for track or modded scoobie use?

And...............

How is motorcycle oil technology totally different?

Looking forward to your reply.

Cheers
Simon

 

As Bob say's he remapped my car the other day and temps are always below 90 deg. Before the oil cooler I would have been looking at 115-120 deg. Must make the car much safer to drive at high speeds.

 

Oilman,

before you ask Bob any questions, can you please qualify the above statement but both Bob and I picked up on as it makes no sense.

I can't imagine why after you have cooled an oil you are happy with to its correct operating range by use of a cooler, you then need to resort to using a thinner oil.

 

Bob,
sounds like you need a cooler...all those extra horses are producing more heat than the system was designed to cope with...126 is v hot imho...does your oil pressure show a marked drop off from the value you have at around 110?...my guess is that it does...which imho is a sure sign that you'd benefit from some additional oil cooling if you want to exploit the power you have to the max..which I'm sure you do!!!

 

oilman, you seem to have gone quiet,

any chance you could answer as I am still confused.

 

Simon is away till next week.

He will be back on it Tuesday/Wednesday.

Cheers

Guy. (Simons Brother).

 

Gone off to search the web at a guess

 

Do not automatically fit an oil cooler. Fit an oil temp. guage first so you actually know you need an oil cooler and even if you do need one you will get lots of valuable info from the temp. guage after fitment.
Cold oil is a BAD thing and an oil cooler could, without a thermostat, increase the problem especially during winter.
Another consideration is the possible increased time for the system to achieve pressure with an oil cooler fitted.
For a road car you are generally driving VERY hard to warrant an oil cooler.

With first hand experience of 5W-30 quality synthetic oils on several tuned engines including a couple of Subarus, I can assure you this is not a viable option for hard, prolonged driving on the Subarus whereas tuned Vauxhall 2 litre 16vs (as an instance)have no problem with 0W-30 oil. Down to clearances I expect.

 

Back again, sorry been away form the office for a week.

I hope that this doesn't cause further confusion but here are the facts concerning temperatures and viscosities.

The point of oil coolers used to be that they helped to keep the oil pressure up in competition engines.

With modern oil pumps, oil pressure drop is rarely a problem, but a lower oil temperature reduces oil degradation, protects oil seals, and helps overall engine cooling.

It also means that a thinner oil can be used. This reduces oil drag and the risk of bearing cavitation at lower temperatures, (Ie, at start-up, warming up, and use in conditions where the engine is not flat-out.)

Some typical Figures:

.................................5W/40................. 15W/50

Visc. at 100C............... 14.90..................18.20

Visc at 110C.................12.06................. 14.53

Visc. at 140C............... 7.09....................8.25

So, at an ‘oil-cooler’ temp of 110C, the 5W/40 is still thicker than the 15W/50 at 140C.

Science and chemistry I'm afraid but hopefully this explains what I'm saying.

Cheers
Simon

 

Science and Chemistry eh.

The point of an oil cooler is to keep the oil you choose to run within its safe limits, modern engines use a combined oil warmer and oil cooler, the Impreza has one of these devices as standard, its job is to stableise the oil temperature within its safe working range as quickly as posible both from cold and from high temperatures.

If you increase the thermal levels by running higher power or longer sustained power runs such as on the Autobahn, you may need to introduce more cooling to the oil system without any change in the specification of the higher than stock grade oil you are already using.

You wouldnt want your oil running at 140 degrees Simon, the oil provides a major engine cooling function that keeps the engine block temperatures under control, when you are working with oil temps you are doing more than just preventing the oil from breaking down, you are looking after the engine mechanicals too, this is especially so on Aluminium engines.

 

So it would appear that if temps are a problem we all agree that a cooler is a good idea if used with a stat .

 

I've been considering a cooler too..
Only managed three to four laps of elvington east circuit before my temps were hitting 110' and starting to rise.
I took it as a sign and came off gently..
Had to wait for it to cool down- then off to play again once temp was back to sensible.

When making hard progress on the road never seen more than 100'