...and it usually works best on a nice sunny weekend with great weather continuing until it is rebuilt.

Then the rain clouds usually move in for a month or two....I have the same early warning detection system on my boat.

OK people here we go for oil viscosity 101. For example....we will use a 20w50 motor oil for the discussion because that is what is mostley used in a boat engines on this site. You can substitute any thing you want for viscosity, the theory is the same. Now, first off, oil does not thicken with heat, it thins. Period. If you don't belive me, pour some 20w50 in a pan and put it on the stove, it will thin. (Oil left for extremely long drain intervals will thicken, we call this oxidation. A whole nother topic.) Conversly, oil thickens with cold, if you dont belive me take some 20w50, put it in your freezer and pour it out of the quart a day later. It will pour very slow. The "w" in 20w50 does not mean weight, it means winter. The 20w50 oil meets a 20w specification at 0 degrees. This specification is set by the SAE. The "50" in 20w50 is tested at 210F or 100C. This specification is also set by the SAE. Please note that there is no "W" after the 50. The SAE only has "W" ratingings up to 25W. As a side point the SAE does not recognize an SAE 70, blenders now call it a Grade 70. You would think that the "50" side in a 20w50 would be thicker than the 20w side but you have to remember that the two viscosities are at different temps, and oil viscosities do not go...0,5,10,15,20,25,30,40,50, 60,75,80,90,140. We are led to belive this with oil because we just don't know. When you start to introduce gear lubes into the mix it get real confusing. A SAE 90 gear oil has the comparitive viscosity of an SAE 50 engine oil, some of the heavier 40 weight engine oils will also have the same comparitive viscosity as a 90 weight gear oil. A 75w gear oil is equal to a 10W engine oil. You must remember that these viscosities are all rated at different temps and on DIFFERENT SCALES. Another interesting point is that all these viscosities have a range that the oil must meet to qualify as a particular viscosity. It woul be like we qualified people by height.........under 5 foot as short, 5-6 feet as med, and over 6 feet as tall, you can have 2 med people one being 5'2" tall and the other being 5"11" tall. Althought both of these people "qualify" by our definition as medium, there is a gross difference in them. The same applies to viscosity. One oil blenders 20w50 can be thicker/thinner than that of another blenders product. The SAE gives you a range to qualify the viscosity in. I personally perfer oils blended to the higher end of the range so when they shear the oil does not fall out of grade or it can handle more fuel dilution before falling out of grade. Some people make a big deal of additive content but your first line of defense against wearis viscosity. It is when this viscosity film breaks dow or thru we then rely on anti-wear additives. Another topic.
We can ramble on forever about this. The bottom line is use a product you are comfortable with. Yes some oils are better than others, but having an oil with a flash point of 400 plus degrees? If my engine oil reached 400 degrees I would have a lot more to worry about than the oil temp. Some oil temps on this thread aren't reaching 200F. I wouldn't use flash point as the only reason to purchase a lubricant. Ken

Minxguy,

What are your thoughts on my experiences with Brad Penn 20-50 oil. (I've copied a previous post from another thread)



I'll share my experiences with Brad Penn oil.
Up until last summer (2005) I had been running Pennzoil 20-50 (engine builders recommendation) I change my oil every 10 hrs and it seemed to work pretty well, no oil pressure issues, oil temps @230 after an occasional hard run 260 (measured before the cooler)
Toward the end of last season I had switched to Brad Penn 20-50 and was not very impressed to say the least. In June I trailered over to Lake Winnipesaukee for Laconia weekend.I had just done a fresh oil change for the trip. We did a lot of boating the first couple days. After three days of running Brad Penn (8 hrs run time) I noticed a loss of oil pressure. My boat normally runs about 60 lbs after warm up while cruising. We were cruising along at no more than 4000 rpm when I noticed the oil pressure dropping. It dropped to 40 lbs, then 30 lbs, I backed down to 3500 and pressure dropped to 20 lbs.
I thought It was engine trouble and stopped for a while. Upon restart, oil pressure returned to normal, 60 psi but soon dropped back to 20 after temps warmed up to normal.
It appears that the Brad Penn oil was all done at 8 hrs and was breaking down at less than 220 degrees oil temp.
I've since changed to Mobil 1 (V-Twin) and all has been fine since. The Mobil oil seems to be pretty consistent, no pressure fluctuations at all and more oil pressure.

Take it for what it's worth, just my personal experience.

Kurt

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I would guess the Brad Penn product fell out of grade. Reason being, when you let it cool down (oils get thicker) the pressure came back until you brought the oil up to temp. The results you are getting with Mobil are typical results with a high quality well built oil. Thats why I have been running Spectro's syn/pet blend product for the past 24 years. Ken

So to sum it up, the Brad Penn oil sheared (broke down?) after 8 hrs and was no longer a 20-50 spec? Is that what you mean by falling out of grade? Does this happen because of excessive oil temps? As I mentioned above the highest temps were 260 for short bursts, measured before the cooler.

Thanks for the reply!

Kurt

Thanks a bunch, very good. I had to print this off for a couple of people to read.

Simply.....yes. I would have been great if you kept a sample of the new Brad Penn and a sample of the old,used oil. You then could "see" what the original viscosity was (and where it falls in the viscosity range) when new and what the viscosity was when used. Your oil temp of 260 is not excessive.........over 300 is excessive. As you elevate oil temps, oil will continue to thin. A multi-vis oil will thin less than a straight weight (due to the polymer). As heavy as a 60 weight is (it is a thicker fluid than a 20w50 at 210), at temps over 210 (say getting close to 300), a 20w50 thins less than the SAE 60, offering more viscous fluid, therefore offering more film strength. If my oil temps we nudging 300 I would start looking at either changing my driving habits or an oil cooler with a thermostat to keep my oil at a min oil temp of say 180F. Ken

fyi...

Mobil-1 15W-50 EP

Merc HP 525

50 hours

1 month in pan

Redlined it 30% of the time

Wix Racing oil filter

Blackstone analysis: No significant wear metals found; oil was at initial viscosity compared to "virgin oil"; no water; additives were getting near reduced levels indicating a change was "on the horizon".

Can your oil do that?

This is a decent writeup but there is a couple errors.

The Kinematic Viscosity of an engine oil is measured in centostrokes (cSt) at 40C and 100C. The Saybolt Viscosity (SUS) is measured at 100F and 210F. No oil viscosities are measured at 0 degrees.

Also, thicker is not always better. There are plenty of cases that have one engine producing less wear metals with a thinner oil than with a thicker oil. People are often fooled into thinking that a thicker oil will protect better. Not always the case.

Ken

One disadvantage to the oil being too thick is it will retain more heat and more start-up wear from late initial flow..

One disadvantage to too thin of an oil is you do not get the cushioning you need and the parts wear a lot faster.

Suffice it to say in offshore motors calling for a straight 40 wt going to 15W-50 or 20W-50 is very safe.