It's Summer Time! Good Oil Temp?

[tooter]

Ok, I've read a bunch of stuff here in the forum about oil temp, so I read some stuff from the VW spec book itself. 'Know what? Ain't much there. But there are some interesting formulas they use to calculate engine output which mention oil temperature on Page M1.6, figures 1-2 "Testing and checking engines" in the VW 181 Service manual.

They want an optimum oil temperature to measure the optimum engine output. For we Type I and II engined folks VW figures this to be "at least" 176F. They measure the oil temperature in a room that is 68F with a barometric pressure of 29.92 iches Hg, which is Sea Level.

So if it is 68F outside and you have the car parked at the beach, your optimum running oil temperature is "at least" 176F. But, what if it's winter and it's only 30F? Well, then your VW should warm up to "at least" 146F. If you're in Arizona and it's 102F, well your oil temp is "at least" 210F.

Your engine will never be able to cool the air, just heat it by "at least" 108F. The oil will always be at room temperature, where ever that room is. Today it was 82F, I pulled in and measured my oil temp with my meat thermometer and it said 190F. When I got home last night it was 64F, my oil temp was 180F. Of course I live in the mountains of Tennessee, it's up hill to the house, air pressure here is not "sea level" and there is probably no account for the accuracy of a meat thermometer. It was indeed "at least" 172F. From the way the dip stick felt, I guess it's at least pretty close.

Magic OIL TEMP formula at sea level: Ambient Air Temp F + 108F = Optimum Oil Temp. "At least"

tooter

[Kubelmann]

I very much enjoyed the result of your research and the data you posted. Heat is the enemy of out alir cooled cars. I have a mostly stock Thing with its orignal dph 1600 and all original tin parts. It does not have cooloing issues. I live in Colorado at 9,000' It usually stays nice here but we have had some very hot summers in the past few years. I also have a high compression big engined offroad Thing that has struggles with temperature issues. I have a pair of racing oil coolers and associated thermostats and valves that will soon be installed. I will report how my new plan will combat the temp issues this car has. It has a t-4 oild cooler and modified cooling shroud along with external oi filter and expanded oil capacity. The modifications to this engine made flaps and thermo impossible to include.. The racing oil coolers I have will mount on both of the 73 Thing vents inside and be plumbed around using high pressure racing oil lines. Different issues create oil temp troubles. Some folks only care about engine head temperature. Others monitor both oil and head temp. I want this car to run at 200 degrees tops. We have 2110 cc prerunner baja car that runs fine in hte dessert but when we bring it up to these mountains it gets hot even when we retune and rejet. That motor does not like the altitiude. It has a single Zenith NDIX carb, low compression for Mexican gas and is built to prerun the Baja. For us cooling improvements are always an issue.

[tooter]

If you place the external oil coolers at the air intakes, wouldn't you pre-heat the air in the engine compartment before it gets drawn over the cylinders? Hot air would just get hotter from the engine. Would it be best to externally mount the coolers with their own thermostatically controlled fans? You might be able to make some sort of bracket and housing that would bolt to either side on top of the rear bumper. This would keep the heated air outside the engine compartment. If you got really excited, you might be able to figure a way to mount them, or at least one of them, inside the cab and use it as a supplemental cab heater in the winter.

From what I understand, a VW engine will add "at least" 108F to the in coming air temperature. So, if you're looking to maintain an oil temp of no more than 200F, you'll need to keep the incoming ambient air, no hotter than 92F. Short of cooling the oil with something cooler than outside air, I'm not sure how to do this.

I think this is one of the properties of anti-freeze in water cooled cars. It raises the boiling point of the water and increases it's ability to dissapate heat faster, so that the now treated water can cool the engine more effectively. My 2002 Eurovan powered Rialta camper keeps a steady coolent temp of 190F on our trips.

With regard to your altitude problem; higher air is thinner air. Perhaps it would just take a larger volume of thinner air to achieve the same cooling effect? Would a higher CFM fan help?

I wonder how the Nazi VWs did in the desert? Little 26hp - 30hp engines pushing and pulling all that equipment AND running 4 wheel drive to boot on some of them!

"Cool projects!" and thank you for your comments!

tooter

[alsehendo]

I thought If you run @ altitude dosen't your engine run richer, thus cooler not hotter. Maybe pulling hard up a steep grade is just taxing you engine more, however I had no problems with a 68 bug going over Logan pass in MT when I was kid which I did hundreds of times. Head temps stayed about the same as down in the flat lands. I alwas ran one bigger jet than normal like I still do today to help keep things cool. With $4.00 gas this may change

[Captain Spalding]

. . . and there is probably no account for the accuracy of a meat thermometer. . .

No, what you need is a candy thermometer.

All kidding aside, I'm not too concerned with finding the optimum oil temperature for optimum engine output. Where the oil is concerned, I'm more fussy about engine longevity than output. Oil has three functions: to lubricate moving parts, to transfer heat, and to hold in suspension soot and other combustion by-products which are too small to be trapped by the oil filter. In regards to this third function, detergent additives are responsible for helping the oil to hold all the crap in suspension and keep it from depositing on parts as sludge or clogging oil galleys, etc.

As the oil temperature increases to high above normal, the detergents break down and no longer do their job - and won't - ever again. As the temperature continues to rise, combustion by-products are produced at a greater rate. Sluge is deposited, varnishes coat every surface, etc. Bad.

So, to my thinking the ideal oil temp is any temperature where the oil is circulating properly and performing its tasks, and not measured in some obscure benchmark-above-ambient. For me the question is at what temperature does the oil start to break down?

The magic number? Some say 210 degrees. I've heard as low as 180 degrees, but that seems pretty low. I have never found out for sure, but I bet a call to Amsoil or one of the other manufacturers would settle this in a definitive way. . .

[Kubelmann]

I think that a 180 temp at top cruise and shifting thorugh tough spots that maxed at 195 would be like a dream come true... I have decided to spend time on this instead of going south. I have that Porsche oil cooler system and am going to plug it into my 1915 high compression set up. I am also including electric fans switched by temerature. I alos have suspension stuff and tires to add...

[Captain Spalding]

I think that a 180 temp at top cruise and shifting thorugh tough spots that maxed at 195 would be like a dream come true... I have decided to spend time on this instead of going south. I have that Porsche oil cooler system and am going to plug it into my 1915 high compression set up. I am also including electric fans switched by temerature...

That's similar to the setup I've got on my 1915. I have an oil temp gauge, and the oil has never gotten up over 190 degrees. The spin-on oil filter adds a lot of peace of mind as well.

[JB181]

I average about 180 to 195 oil temperature and CHT 325 to 350. My engine is a 1914 with DTM 8.5-to1 compression ratio.

J.B

[tooter]

I've done some more homework on this oil temp thing.

Again, in the VW 181 manual under Tech Specs, VW talks about oil grading. The "W" as in 10W, means Winter. This is the viscosity of the oil in Winter when the oil temp is 0 degrees F. The 30, as in 10W-30, or 30HD, is the viscosity as measured when the oil temperature is 210F.

So, it seems the oil makers and SAE standards, measure the viscosity of the oil at 0F and 210F. If your oil temp is 210F, you are running within the operating perameters of the oil.

If you can find or have your old Thing owners manual, look at the page that shows what grade oil to use under what outside temperatures. Now add my affore mentioned "at least" 108F to those temps and you see where the overlaps are and why VW recomends 40 wt as 30wt specs far exceed 210F optimum oil temp as the outside air temp increases. VW even states that "tolerances can be exceeded for brief periods of time".

Special Note - I buy synthetic oil for my water cooled VWs since this is what they are filled with from the factory and dealer. I had been told that synthetics run cooler. Uhhh... not from what I just experienced.

I tried some Synthetic oil in my Thing. Temperatures ran HOTTER than with "natural" oil, by 12 degrees or more! It might be cooler in water cooled engines, but in my short 500 mile experience, Synths run much hotter. The weather is warming up here, averaging upper 70s-low 80s. So I filled her up with straight 40HD. Old school, I know. But safer, I feel.

[Kubelmann]

I wanted to post the John Muir human oil temperature gauge test..

1. Drive car a "normal" distance.
2. Turn off car
3. Go to rear of car. Open engine door.
4. Attempt to remove dip stick.
5. If it is too hot to remove then the engine is too hot.
6. If you can remove it then everything is OK

If the dip stick is too hot:

Check oil level, timing, valve adjustment, dwell, spark plug condition, belt tension, carb adjustments, cooling fan for waste material, flap thermostat function, general engine clendliness (caked oil holds in heat..

This list was not written in order of importance. It is not a complete list of the issues that can cause an air cooled vehicle to run too hot...

[alsehendo]

Use a CHT much more important is head temps.

I herd not all Synthetics act the way described & Moble One will run hotter and some others not. The type 4 guys say Royal Purple and Valvoline Synthetic run cooler. I amgoing to try Royal Purple next change.

http://www.shoptalkforums.com/viewtopic ... yal+purple

[Captain Spalding]

Use a CHT much more important is head temps.

Okay, I'll bite. Would you care to flesh out that rather terse assertion with some facts/details?

[wildthings]

When you are measuring oil temperatures you are not seeing the maximum temperature that your oil reaches, but more like the average or perhaps even the lowest oil temp in the engine depending on where you measure it. The oil near the top of the cylinder and inside the valve covers will get much hotter than the oil elsewhere in your engine that you can actually reach to measure. A CHT gauge will give you a much better reading of your maximum oil temperature than will an oil temperature gauge.

[alsehendo]

I have had relatively low oil temps and high head temps but not vise versa. I don't think oil temp gauge is total protection like I once thought. I found out the hard way with a cold weather OK oil temps and still a cooked engine. CHT is also a imediate indication of lean mixture--as all pilots know.

I don't think high, however oil temps should be ignored--sorry about the tersedy of the post if this is even a form the word. It was blunt @ best.

[Captain Spalding]

I have had relatively low oil temps and high head temps but not vise versa. I don't think oil temp gauge is total protection like I once thought. I found out the hard way with a cold weather OK oil temps and still a cooked engine. CHT is also a imediate indication of lean mixture--as all pilots know.

I don't think high, however oil temps should be ignored--sorry about the tersedy of the post if this is even a form the word. It was blunt @ best.

Thanks for that clarification. So if one has a CHT gauge, what should it be reading? How hot is too hot?