With the last Vanagon I owned, a 91 Carat, it had a tendency to run hot when I bought it.    I flushed the cooling system and it seemed to be controlled.
Then I changed the oil from Castrol 20-50 to Mobil 1 15-50 synthetic.    On the next trip I drove it on which was a couple of hundred miles, the temp needle started where it useally was.   Then I noticed after about 30 miles as I was driving that the engine temperature started dropping.    It went from about 5/8 of the scale down to about 3/8 of the scale.    I have no figures but I am absolutely convinced that the use of that synthetic oil made that engine run cooler.    It never again ran with the needle any higher.  I live in the hot south east and I tend to drive on the fast side, around 80, for extended periods of time.

This is just my experience and my opinion.

Steve

-----Original Message-----
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
To: vanagon@GERRY.VANAGON.COM
Sent: Wed, 12 Mar 2008 11:46 am
Subject: Re: diagnosis of high oil temperature--is my engine dying?

High oil temperature is the Achilles heal of the Water Boxer and is probably 
the true leading cause of rod bearing failures. I have done a lot of 
experimenting and it does not take too many things going wrong to put the 
oil system into thermal run away and actually have the pump stop pumping and 
bearing failure shortly there after. 
 
The main causes of high oil temps in an other wise normally functioning 
system are high revolutions under load and over filling. Even with a fairly 
large oil cooler, I can get oil temps to go out of control with the oil 
level as little as a 1/4" above the max mark. When I do oil and filter 
changes, 4.5 quarts is full. The goal is between the marks, not the full or 
max mark. 
 
Oil temperatures seem to be a problem when the engine is operated near 4,000 
rpm or above for extended periods. Under 4,000 rpm the stock oil cooler will 
do a fair job at keeping the oil close to coolant temperature. As the oil 
temperature goes out of control, oil pressure falls both due to reduced 
viscosity and clearances in the pump and bearings increasing which reduce 
pump capacity and increase bearing flow. 
 
For trouble shooting, you need to make sure the oil cooler is actually 
getting proper water flow. For additonal upgrades or corrective measures, in 
warm climates you can feed the oil cooler from a cooler water source instead 
of the engine outlet. On a number of vans I have eliminated the stock oil 
cooler and installed a 16 or 19 plate flat cooler in front of the radiator 
and used a sandwich adapter and remote thermostat. This has worked on Fun 
Bus for 254,000 miles now and that engine still holds 10 psi at idle and 
almost 45 at highway speed. Oil temperature will normally run between 180 
and 210. Yes, even in winter if I do 75+ for any length of time the 
temperature will climb and then as soon as I slow down it will drop to the 
180. 
 
For oil filters, I have now come across 4 engines, (2 mine) where oil 
testing has shown the Mahle filters are not great filters for extended oil 
change intervals. The Fram TG2870A and Mobil 1, 205 still get good results 
after 7,500 miles. 
 
Caterpillar has a great reasonable oil sampling program. Depending on 
quantity you can get testing done for under $20. You can also get antifreeze 
tested. With good filters the Waterboxer does well at 7,500 mile change 
intervals. Oil nitration, ( high ring ring temps.), becomes an issue after 
that with Mobil 1. My Fox was on the once a year , 14,000 mile plan on the 
TG filter. When I changed to the Mahle, I got warning results at 7,500 due 
to dirt and wear particles. Now with the Mobil filter, results were good at 
7,500. Will test again at 10K, (next week). This car is now seeing some 20K 
per year. 
 
Dennis 
 
>From: Ben S <phlogiston420@GMAIL.COM> 
>Reply-To: Ben S <phlogiston420@GMAIL.COM> 
>To: vanagon@GERRY.VANAGON.COM 
>Subject: Re: diagnosis of high oil temperature--is my engine dying? 
>Date: Tue, 11 Mar 2008 17:18:31 -0700 
> 
>thanks for the input guys. i don't think this is a cooling problem 
>either, since i first observed this problem in december after driving 
>around all summer with good oil pressure. i like the idea of having 
>the oil tested... unfortunately i just changed it and have only about 
>400 miles on the new oil, and the old stuff is in a drain pan mixed up 
>with residual used oil from my motorcycle and my sister's wrx. i 
>guess i will cross my fingers and hope that at least my engine makes 
>it until the next oil change! 
> 
>how hard is it to check the end play in the crank? can this be done 
>from the "front" belt pulley end or does it require dropping the 
>tranny to check at the flywheel? 
> 
>thanks for heads up on the oil testing, though--i'll certainly take 
>that route if wendy survives to her next oil change! 
> 
>Ben. 
> 
>On Tue, Mar 11, 2008 at 3:17 PM, Scott Daniel - Shazam 
><scottdaniel@turbovans.com> wrote: 
> > 
> > My 3 main thoughts : 
> > 
> > 1. I can't think of any reason the oil should be getting hotter 
>than it 
> > used to, under the same conditions. Your cooling system and coolant temp 
> > sound just fine as usual, and well maintained. And I can't imagine that 
>now 
> > the oil cooler is suddenly less efficient – but do consider that, but 
>seems 
> > very unlikely to me. 
> > 
> > 
> > 
> > 2. since you are so interested in staying on top of this – bravo - it's 
> > strongly indicated that you should send an oil sample (after 3,000 miles 
>on 
> > it, or at an oil change ) to an oil lab for analysis. 
> > 
> > Hergurth lab I think in Vallejo, if they still exist. They tell you 
>about 
> > 40 things about the oil, including abnormal amounts of bearing and ring 
>and 
> > piston material metal. And you can talk to an oil engineer too about 
>your 
> > engine. I can't recommend this strongly enough , and I can't think of 
>one 
> > time any vanagon owner was smart enough to avail themselves of this very 
> > valuable service. Costs maybe 45 bucks. 
> > 
> > 
> > 
> > 3. I think it's engine wear – likely bearings. I've read of a few 
> > people replacing the oil pump to help with this, though oil pumps don't 
> > usually wear much. One very brief fast simple small test that might 
> > reveal something, you can check crankshaft end play. If that's 
>significant 
> > that would point to main bearings. Or main bearings loose in the case – 
>a 
> > vw malidy. 
> > Them vw's ya know. I am seeing more and more that a waterboxer is 
>just 
> > a traditional 1600 type air-cooled engine beefed up and adapted to water 
> > cooling. Perhaps future Subaru power is indicted in your case. 
> > 
> > 
> > 
> > But seriously, consider that oil analysis. You can really learn a lot 
>about 
> > your engine's condition. 
> > I'm mildly frustrated because it's my experience that very seldom 
>do 
> > people hear about some 'new thing' to them – a book, an herbal 
>supplement, 
> > or whatever, and check it out. 
> > 
> > They tend to stay thinking they already know everything there is to 
>know, 
> > which is a joke of course. I hear of some new thing – I want to check 
>it 
> > out, or at least be very informed about it. 
> > And I've recommended oil analysis in cases like yours many times, 
>and 
> > have yet to hear of one person doing it. * It's like they'd rather 
>wonder 
> > and speculate and yak on lists about it, rather than get factual 
>information 
> > to work with. * 
> > 
> > Very brief story- had this customer with an oldish 240 volvo. The 
>engine 
> > was just noisy and 'odd' ,. compression wasn't horrible, but the engine 
>was 
> > just 'tired in a very nebulous way'' ( old volvo's are like that) . The 
> > woman was German too – after the analysis came back, showing several 
>metals 
> > about 60 % higher than they should be , we knew – her engine was 
>'kaput." 
> > 
> > Scott Daniel Foss 
> > 
> > www.turbovans.com