Date: Sun, 8 Aug 2010 09:59:59 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Oil overfill... or not? (long post)
In-Reply-To: <20100805105630.L6QAX.1329966.imail@eastrmwml32>
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Outside temp alone should not have much effect on oil temp unless the radiator is near the end of its thermal capacity, (thermostat not fully in control) or things are so hot that oil cooling through the case is making the difference. During those bad weather periods you were probably also driving slower and just a few hundred rpm makes a big difference.
Try reducing the oil level and see what happens. Synthetic oils can maintain viscosity at temperature extremes but there normal viscosity is slightly lower. They do have lower pumping losses though so they add less heat to the process at high speeds. They do last longer so the increased change interval offsets the higher cost. If you consider the cost/mile for 7,500 mile change intervals the oil cost becomes insignificant compared to fuel.
You really need an oil temperature gauge to see what is going on. Make sure the oil cooler actually has water flowing through it.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Dave Mcneely
Sent: Thursday, August 05, 2010 10:57 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Oil overfill... or not? (long post)
There has been lots of discussion on here about oil fill levels over the time I have subscribed to the list. The idea of the oil stick having a mark which says "max," and that being, according to some on the list, "overfill" has always puzzled me. If that is overfill, I reasoned, then why would it be marked "max"? Why would a lower level not be marked so? Surely the VW engineers knew what they were doing when they chose that level as "max"?
So, having had work done by Darrel of Darrel's Hobby Shop in Norman, Oklahoma, David of Bavarian Autohaus in Norman, and Barry of Downtown Auto in Spokane, Washington, and having come to trust all three, I put the question to each of them. Their answers were that that was the maximum fill level, and one should routinely fill to that level when changing the oil. They also said it was not necessary to add oil unless the indicator showed at the min level or below, but that it would not be harmful to do so to keep the level at max. I told them about members of the list stating that one should not fill the oil level above the mid-position between the min and max marks. They each found that passing strange, pointing out that the max mark means exactly that, max, and not overfill.
Since at least one list member had so stated, I told them that I had been told that filling to the max level allows the oil to froth and lose pressure. Barry told me that all oil froths from the pump action in all vehicles. He further stated that if filling to the level marked max on the stick were overfill, then the engineers would have chosen a lower level to mark as max.
Barry owned and operated a VW Vanagon GL Campmobile for many years, driving it in Baja and Southern California regularly, and he services a good many Vanagons. He is, so far as I can tell from inquiries I made, an excellent mechanic and businessman, and a preferred Vanagon service provider in the Spokane area. I know that he went out of his way to shift service commitments around in order to provide service to me since I was in need of getting back on the road on two separate occasions (last summer and this summer). I had him change the oil in my camper when I was in Spokane, since I really did not have a place where I could easily do it myself. Both Darrel and David have provided excellent service to me, both shops have serviced Vanagons and other VWs for years, and David's chief mechanic was trained at VW training facilities in Germany. David owns and drives a '91 Campmobile.
Beyond these questions about the fill level and three excellent VW mechanic's opinions, I wonder concerning my own vehicle's behavior. I have an aftermarket oil gauge mounted (Darrel installed it, along with the proper sensors matched to the dynamic oil pressure monitoring system and the gauge). When the engine is cold, the pressure runs quite high, around 70 psi on a summer day, but it drops as the engine warms. I assume this is normal. If I drive short distances and the ambient temperature is moderate (say in the range of near freezing, to around 90 F), once the temperature gauge reaches the normal position with the needle exactly hiding the red LED, the oil gauge generally runs around 30 psi. If the ambient temperature is in the high 90s F or hotter (it ran as high as 110 at times on my return trip to Oklahoma earlier this week, hottest after I got back into my home state's western reaches), and I drive at highway speed (60 mph) for a sustained time, the oil pressure gauge reading will drop to around 20 psi. During these oil pressure excursions, the temperature gauge needle stays solid on the LED. If I stop, dropping the engine speed to idle, the oil pressure light will blink briefly, maybe staying on for bit unless I raise the rpms momentarily to around 1200. It then goes off and stays off when I allow the rpms to drop again. I do not always have to raise the rpms briefly, as the light goes off on its own after just blinking a couple of times. The oil pressure indicator light never blinks when I slow to idle if the oil pressure gauge is indicating 25 psi or higher at higher rpms.
When I was on my outbound drive in northern NM three weeks ago, it was pretty hot as I crossed the prairies east of Raton, NM, temperatures running high 90s F. The temperature gauge showed normal, that is exactly dead center on the LED. The oil pressure gauge was reading about 20 psi, which it seems to regularly do in such circumstances. As I moved onto I25 from US 87, and began the climb to Raton Pass (6% grade), an intense thunderstorm developed, with wind, hail, rain. The outside temperature dropped into the fifties, and the oil pressure gauge indicated a rapid increase in pressure to around 40 psi. The temperature gauge never varied from its solid position centered on the LED. The air temperature remained low as we crossed the pass and descended, and on the descent, the temperature gauge did drop a little (which I surmise is normal on a steep descent, as the engine unavoidably air cools considerably ). So long as the ambient temperature remained low, the oil pressure indication remained around 40 psi. As we moved back onto lower terrain and the air temperature rose back into the nineties, the oil pressure indication also dropped, back to 20 to 25 psi, where it generally runs under similar conditions at highway speeds.
Throughout our 5800 mile trip, whenever ambient temperatures were moderate or low, the oil pressure after warmup and at highway speeds would run around 30 psi, sometimes higher when it was quite cool outside. If the temperature rose into the nineties, though the temp gauge continued to show normal (needle centered on the LED), oil pressure would drop as I reported above to around 20 psi. On the hottest leg, Monday in Oklahoma, oil pressure dropped to between 15 and 20 psi. The warning light never came on except briefly blinking at idle (and when I lugged the engine a couple of times when stopping on hill, but again it was brief and stopped).
So, this beast has a factory oil cooler, as we all know. Do these sometimes go bad, perhaps having either oil or coolant channels partially blocked? Is oil temperature (separate from coolant temperature, which is picked up on the thermostat housing I believe) the likely reason for these variations in oil pressure indication as I suspect? If so, is there a fix, so that oil pressure remains at 30 psi or so even at high ambient temperatures, and does not drop below 5 psi (which brings the blinker on I believe) at idle?
I use 20W - 50 conventional oil, Pennzoil on the out bound trip to Spokane, changing to Valvoline in Spokane. I was using Castrol 20W-50 prior to this, with similar behavior, but choose no longer to use Castrol for reasons unrelated to its performance. I use Mehle filters. I have no idea what oil the previous owner used, but the van had a Fram Toughguard filter when I got it (it had 139K chassis miles at that time, April 2009). The engine is a rebuild installed at 110K chassis miles by the previous owner, and the chassis now has 155K miles. Though I am reluctant to use synthetic oil for a variety of reasons, not least being price, do synthetic oils maintain pressure better at high temperatures?
BTW, that hail storm on Raton Pass was intense. We only experienced moderate hail with stones a cm or so diameter and falling briefly, but as we neared the top of the pass, hail was accumulated on the ground to well over a foot deep, drifts 2-3 feet, and snow plows were active (road already cleared on our northbound side, still hail covered southbound as we entered Colorado, where snowplows were also active).
David McNeely
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