How can i reduce Oil temps?

[dparm]

What's not to understand about a 5w40 recommendation? Audi wants oils with sufficient HTHSV and there are very few 5w30s and 0w30s with HTHSV >= 3.5.

Agreed that they're building in a bit of a safety margin, but don't you think that if they could get away with running ANY 5w30 they'd just spec that? Audi doesn't just arbitrarily decide what oils you can run.

 

[CATERHAM]

Originally Posted By: dparm

Agreed that they're building in a bit of a safety margin, but don't you think that if they could get away with running ANY 5w30 they'd just spec that? Audi doesn't just arbitrarily decide what oils you can run.

It's a good question.
Remember before the advent of 0w30 and 0W-40 oils Audi like all OEMs used to spec' 5W-20 and light 5w30 oils based largely on ambient temperature.
The reason they no longer spec' lighter oils is because they don't need to because a high VI 0W/5w30 synthetic will perform adequately in the winter. Yes it would be beneficial to run a 0W-20 in winter in many applications but what happens if you don't change out the oil in the summer to something heavier and then drive flat out on the autobahn with 15,000 miles already on that 0W-20 oil and you're down a litre or more? Increased engine wear could be very likely.
So from an OEMs view point it's better to simply no longer spec' a 20wt oil or even a light 30wt.

Even in the summer does Audi and most other European makes actually require a heavy 3.5cP HTHSV oil from a lubrication perspective? Based on my experience the answer is no, even driving at autobahn speeds, but if one does drive routinely at high speeds, oil consumption will be higher and a heavier oil will provide a lower consumption rate under such conditions.
An acceptable oil consumption rate, particularly with the often long European OEM OCIs, is a major factor that goes into the recommended oil grades.

If one thinks they drive their German car pretty hard and are uncomfortable running an oil lighter than 3.5cP I suggest installing an oil pressure gauge to see what the actual operational viscosity is. In all likelyhood what you'll find is that you don't come close to testing the minimum viscosity requirement for your engine and that a somewhat lighter 3.0-3.2cP 0W/5w30 oil will in fact provide more efficient overall lubrication.

 

[dparm]

My car makes 410hp. I use all 410 on a regular basis, even in the winter...so I'll stick with my ACEA A3/B4 oils.

Your points are valid, CATERHAM. Like many other things on the German cars, they're overengineered in the US market since we don't have things like the Autobahn. (brakes, cooling, tire speed rating, oil, etc)

 

[CATERHAM]

Originally Posted By: dparm
My car makes 410hp. I use all 410 on a regular basis, even in the winter...so I'll stick with my ACEA A3/B4 oils.

More importantly, you don't have an oil pressure gauge so you don't know how much viscosity reserve you actually have at any given time. With that in mind your approach is a prudent one.
Hopefully, one of these days you will get one installed as every serious oil geek should have one on at least one of their cars.

 

[Brit33]

Caterham:

I have an oil pressure question in relation to oil flow.

The alfa manual of my car states the max oil pressure at 5500 rpm should be between 60-88 psi.

The bypass valve is fully open at 88 psi. This works spot on.

When the engine is hot I will reach 55-60 psi max.
Or at 3000 rpm it will reach about 45-50 psi. As we know it's not a linear increase.

Would you say this is in within good limits and the oil isn't too thick? Is the oil flow sufficient with this oil as it doesn't go over 60 psi when hot?

At idle like some typical alfas it drops to about 10-12 psi.

Using Castrol 10w60 (HTHS 5.3).
I'm afraid if I drop to a 50 oil the idle pressure will be too low.

 

[CATERHAM]

Brit33, sorry for not responding earlier when you first posted the question.

Yes, based on your OP figures the Castrol 10W-60 would not appear to be too thick at all. Do you know "hot" oil temp's you're actually acheiving?
What is the recommended oil grade on which the factory OP spec's are given?
I'm not surprised when you say many older Alfa Sud owners have OP issues as the spec' oil is undoubtedly not as heavy as what you're running. I'd continue to use the Castrol 10W-60 although form a purely interest viewpoint I'd like to know why such a heavy oil is necessary to maintain adequate OP. Is it bearing wear after a certain amount of mileage?

 

[Brit33]

Originally Posted By: CATERHAM
Brit33, sorry for not responding earlier when you first posted the question.

Yes, based on your OP figures the Castrol 10W-60 would not appear to be too thick at all. Do you know "hot" oil temp's you're actually acheiving?
What is the recommended oil grade on which the factory OP spec's are given?
I'm not surprised when you say many older Alfa Sud owners have OP issues as the spec' oil is undoubtedly not as heavy as what you're running. I'd continue to use the Castrol 10W-60 although form a purely interest viewpoint I'd like to know why such a heavy oil is necessary to maintain adequate OP. Is it bearing wear after a certain amount of mileage?


No worries Caterham. Understand this is a very busy forum.

Original spec oil is AGIP 10w50. (no longer made unfortunately).
But of course this is for a new car made 25 years ago. I still have the original crank but new rod end bearings and 1 new main bearing recently put in.

I've got an oil temp gauge/sensor but not in the ideal place at the moment.(main oil channel on the block)
I have an oil dipstick sensor being sent to me in these weeks so I will come back with accurate readings then.

I was concerned about not enough flow through the bearings but as we see the oil pressure is not on the high side which gives us some indication.

The main journal clearances were between 0.055mm and 0.060mm.
Max is 0.063mm allowed before a re-grind (or new crank).
Oil pump gears are new. Closest clearance possible.

Thanks

 

[Mitch Alsup]

First of all: 225dF is not very hot for a xxW-40 oil. That kind of oil will likely keep your engine well lubricated until 275dF and maybe well lubed up to about 300dF. So you have nothing to worry about at 225dF. Plenty of margin.

Second: there is a very strong relationship between oil viscosity and oil temperature. So strong in fact, that knowing the 40dC viscosity adnthe 100dC viscosity will allow you to compute the actual viscosity between -10dC through +150dC with high accuracy.

Thicker oil does take more power to push through the engine, this extra drain on the power adds heat to the oil.

Finally, there is no rational to wanting to keep your oil at 212dF. 200dF is where the additive package starts to work, 212dF is where water vapor is released at rapid rates, leaving the unmolested oil behind. Hotter oil is thinner and thinner oils lubricate various engine parts better.

As a comparison, in my track car I ran an experiment on oil thickness and oil temperature. I used a 3W-30 oil, a 5W-40 oil and a 15W-50 oil (this was a few years ago). The 5w30 oil ran 273dF, the 5W-40 oil ran 275dF, and the 15W-50 oil ran 285dF. Thus, the kinds of oil temperature change with grade-weight change is measurable but miniscule.

But if you really want your oil to be at a particular temperature (for whatever reason) an oil cooler with a thermostat is the best option.

 

[Leonardo629]

my M3 gets up to operating temp in under than 10 min of freeway driving now that I'm running 0W40, didn't really pay attention though when I was running TWS 10W60 though...

 

[Nederlander75]

This summer I’ve started running 20w50 in my RX8 as an experiment. While not related to my experiment I think that I’ve observed lower operating temps with heavier oil, though I haven’t got any real method to make this determination. However, what makes me feel that operating temps MAY be lower is that my shut down cooling fans only come on when ambient temperatures are above 90F versus last summer when I was running 10w30 and 0w20 and the fans would come on at 80F. These fans come on when the engine compartment temperatures are 210F or above at shut down or if the temp spikes after shut down. Its likely the observation is unrelated, but interesting to me none the less. I notice about 5% worse fuel economy and my top speeds on the back straight of HPR are about 5-7mph lower on the 20w50 but that could also be heat related.

 

[Garak]

Nederlander75, there are a lot of people who don't think a 5w-20 (or even a 5w30) belongs in a rotary in the first place, so perhaps you're onto something there.