VW Baywindow Bus - VW Engine Oil Specifications

by Richard Atwell
(c) Copyright 2020-2021


I've compiled oil temperature and pressure specifications from several sources into this reference guide along with the relevant maintenance sections from the bus owner's manual (1978) and service manuals.

Companion Articles:

VW's Warm-up Advice:

VW's advice on idling ("How you drive" bullets #3 and #4) is NOT good advice to follow.

VW specifically says not to engage in "warm up idling" because it wastes gas:

warm up

In practice the engine will accelerate better and the transmission will shift better if you let it warm-up a little first. Why? Simply because it's older technology and not engineered like a new vehicle with the "turn key and go" expectations.

Try this in winter: start your car and see how long it takes for the water vapour present in your exhaust to disappear. Use a newspaper to catch the vapour to make sure it's water and not smoke. Some of the vapour will be coming from water that condensed in the exhaust overnight. When this vapour goes away, the engine and transmission will have fully warmed-up fully.

Is it worth waiting 10-15 minutes? Probably not, but 3-5 minutes or more would be worthwhile and depending on freezing ambient temperatures, longer.

VW's Cool-down Advice:

VW's cool-down advice (On the highway... #7) is NOT good advice either:

cool down

If you turn-off a hot engine, especially an overheated one it will "heat soak" without any cooling from the engine fan and the temperatures will temporarily increase. This will require you to let the engine sit for an extended cool-down period before restarting.

The VW advice seems more based on the liability of you falling asleep in the bus and breathing in some of the exhaust during idling ("See warning on Engine Exhaust").

In hot weather, it's always best to let the engine idle for a 3-5 minutes before turning it off so that the engine driven fan can cool down the engine to a normal engine temperature level. No engine fan running = no cooling with air-cooled engines!

Oil Consumption:

The 78 owner's manual states that it's normal to burn up to 2.4 qt. per 1000 miles. I think that number is WAY too high especially for a new engine and my explanation for this is that the oils they tested back in those days had a much lower flash point and burned off more easily.

I hardly burn a measurable amount of oil in my well used mid-life engine driving within the city but on long highway trips I'll burn a 1/2 quart of synthetic over 3,000km of highway driving because the heat from the cylinder wall will vaporize the oil in addition to the oil that gets sucked into the combustion chamber.

oil levels

PS. Your dipstick may have a shorter handle than the one depicted in the photo. ;-)

The dipstick reads 0.5L between the two marks and VW recommends checking the oil level at the gas station (take about the old days!) which I skip as a general rule unless it's summertime and I'm on the highway a lot.

Frequency of Oil Changes:

How do you maximize engine life?

  1. Automobile manufacturers recommend specific engine oil grades for their engines at specific temperatures. Period.
  2. They also specify maintenance intervals that are based on mileage AND season.
  3. They do not specify oil additives and often recommend against them.

Here's what the 1978 Maintenance Manual (CDN) that came with my Westfalia recommends:

As per VW: an oil change every 12,000km (7,500mi) OR every 6 months!

Those are the maximum intervals between oil changes as of 1978 using SE grade oils with their SE additive packages.

So what's changed in 40 years since the SE rating went obsolete:

These things haven't changed:

One way to determine how much water you are collecting in the crankcase is to remove the oil strainer on the bottom (not the oil filter). Look for white pudding like in the photo which is an oil and water emulsion resulting from water condensing out of the air:

This is the best reason to change the oil every 6 months as per VW: water contamination of the engine oil.

When it gets really cold, you may even find a white pudding inside the large diameter vacuum hoses that are connected via the oil breather including the S-boot on FI models. You may also notice it under the oil cap and clinging to the inside of the oil filler tube. Yuck!

1978 Owner's Manual Oil Advice:

Have you ever read the owner's manual that came with your bus? Was it lost?

Luckily many classic VW manuals have been scanned and cataloged thanks to the hard work of volunteers in the VW community like Everett Barnes who runs theSamba.com.

Here are all the oil references from the 1978 Owner's Manual all in one place and highlighted:

when to add oil

Page 6: remember when gas stations had oil on display between the pumps? You should carry at least 1 qt of engine oil in your bus at all times.

oil warning light

Page 18: take note above where it says, "An occasional flickering of the oil pressure warning light when the engine is idling after a long high-speed trip is no cause for concern if the light goes out upon acceleration."

While VW says no cause for concern, unless this is happening with SAE 50 oil, you should check your oil pressure at speed and switch to a thicker grade of oil.

winter operation

Page 50: take note of the advice on changing the oil due to driving short distances during the winter months.

changing the oil

Page 57: The torque for the drain plug is 16 ft.lbs. The torque for the oil strainer is 7-9ft.lbs. and MUST be adhered to or you will risk damaging the center support for the camshaft (yes this is a design flaw).

Tighten the oil filter hand tight. A special tool is only required if it's been overtightened. I find a jar opened works in some cases. In more severe cases, you'll need a filter wrench.

oil sump capacity

Page 77: I change my filter whenever I change my grade of oil. Otherwise I tend to change it every second oil change until my mileage driving during the season has been minimal.

oil grade chart out of date

Page 81: the note about API SE oil grades is out of date. See my Engine Oil Selection article for updated advice.

gas station quick reference

Page 84: When I change the oil, I usually put 0.5L in the filter and 2.75L into the engine and run it for 5 minutes and look for any leaks.

I then check the oil level again in the morning and top it up according to the dipstick and it usually needs exactly another 250mL.

VW's Bus Engine Specs:

VW's oil charts fail to mention one important detail: they were recommendations for a NEW engine only. As the engine ages, the bearing clearances increase and you need to use a thicker oil to maintain surface tension and oil pressure. What's good for your engine isn't necessarily good for someone else's engine simply because of the difference in mileage and actual wear between the two engines.

A way to refine the choice of grade for your climate is to benchmark the oil pressure against the VW specs however data available is in question:

Source Page Description RPM Oil Temp Oil Pressure
Bentley Type 2 68-79 Engine & Clutch, Page 26, Section 9.3 Type 2 with Type 1 Engine, Single-carb 2500 70C 3.0 Bar
Bentley Type 2 68-79 Engine & Clutch, Page 26, Section 9.3 Type 2 with Type 4 Engine, Dual-carb and FI 2500 70C >= 2.0 Bar
Without Guesswork
Types 1,2,3,4
II Tolerances, wear limits and settings p12 Types 1/1600, 2/1600, 3/1600 2500 70C 3.0 Bar (new), 2.0 Bar (wear limit)
Without Guesswork
Types 1,2,3,4
II Tolerances, wear limits and settings p13 Types 2/1700, 1800 and 4/1700, 1800 2500 70C 3.0 Bar (new), 2.0 Bar (wear limit)
914 Porsche
Technical Specifications
Tolerances & Wear Limits p16 914 1.7 and 1.8 Liter Engines 2500 70C 3.0 Bar (new), 2.0 Bar (wear limit)
914 Porsche
Technical Specifications
Tolerances & Wear Limits p21 914 2.0 Liter Engine 2500 70C 4.5 Bar (new), 2.0 Bar (wear limit)
Yellow Workshop Manual Engine - Lubrication System 17.4 Type 2 with Type 4 Engine 2000 80C 2.0 Bar
Bentley Vanagon 80-91 Engine - Lubrication System 17.3 Type 25 Air cooled-AFC 2000 80C 2.0 Bar
Bentley Vanagon 80-91 Engine - Lubrication System 17.7 Type 25 Diesel 2000 80C 2.0 Bar
Bentley Vanagon 80-91 Engine - Lubrication System 17.9 Type 25 Water-cooled 2000 80C 2.0 Bar

Printed Errors: Bentley wrongly converts 2.0 Bar to 28 psi but it actually converts to 29 psi. Similarly 42 psi is printed when 3.0 Bar converts to 43.5 psi. There is also no distinction between single and dual relief cases.

So looking at the table, which is it? 70C or 80C? 2000 or 2500 rpm? 2.0 Bar or 3.0 Bar? And why are the VW specs all over the place? I suspect, all the perceived errors are based on copies of only half the information that only relied on the wear limit without stating as such.

Temperature specs:

Which temperature depends on your thermostat: these are the same temperature thresholds that cause the early model thermostats to begin to expand (65-70c) and activate the fan shroud cooling systems (air deflection flaps). Read my VW Baywindow Bus Thermostats Explained article to learn which one you have (or should have).

If you have an accurate oil temperature gauge AND an oil pressure gauge AND a tachometer on your automotive multi-meter you are closer to determining if your choice of oil meets the VW specs. If the reading drops substantially below 29 psi you would probably benefit from switching to a thicker formulation.

Easy right? Not quite. What complicates testing is the fact that it's hard to hold the engine to 70-80C for long and it's not clear where VW intended you to take the oil temp reading although we can make a best guess. Most oil temperature senders are installed in the Type 4 inspection plate which is in the corner of the case. VDO senders are also slow to respond and usually attached to a plate which acts as a heatsink.

I've written about the limitations of using VDO gauges that give you an indication of when the engine is working hard but that's all. It's a pity that VW didn't include more gauges or warning lights in the instrument cluster (both air and water-cooled) but this lack of gauges descends from a time when so many things we take for granted were optional equipment or expected to be provided by the aftermarket. Even the gas gauge was non-standard feature at one time in history.

oil temperature thermometer

I get the engine warmed up at idle for 10 mins and then take the reading from the base of the dipstick using a 300F thermometer from a scientific supply store. I'm somewhat weary of the thermometer breaking. One day I'll purchase a cooking thermometer digital solution which is as equally immersive in the oil.

All tests are to be conducted using SAE 30 only according to spec. Using my viscosity chart, you'll see that either 5W-30 or 10W-30 has nearly the same viscosity as SAE 30 at this temperature [yellow/red bars] so use those grades instead.

Speed specs:

Which speed is somewhat irrelevant as in practice there's not much difference in witnessed oil pressure between the two engine speeds, however I believe the rpm values in the table to be tied to the test temperature settings after comparing all data.

Pressure specs:

Good grief! What a mess. My best guess is that at your thermostat temperature and at the specified rpm, the range of oil pressures should be between 2.0 Bar and 3.0 Bar for most engines. If you have a case without the oil control valve (single-relief) then it could reach the 4.5 Bar level. I'm still researching this detail but it certainly jives with my GE engine with hydraulic lifters (noting that no 2.0L 914 was ever fit with hydraulic lifters) and Berg believed that Hydraulic cams and lifters benefitted from a 30mm pump that delivered higher oil pressure.

Some Type 4 engines (mostly ones with Hydraulic lifters) lack the oil control valve (otherwise known as a dual-relief case) because the hydraulic lifters do the bleeding.

Since an oil pressure gauge only costs about $30-40, I recommend you use it to determine if you oil grade selection fits your engine's current needs and see if you can get in the ballpark of a suitable oil pressure. You may be surprised how HIGH your oil pressure is to begin with.

Operating Conditions:

The engine oil temperature depends on the rpms and outside temperature by and large. As the engine rotates faster, so does the cooling fan but when it's 100F outside, there is less capacity to bleed off the latent heat produced by the engine. Therefore driving at 65-70mph is unwise in very hot weather.

Engine State Oil Pressure Oil Temperature
Startup High due to thickness of oil Ambient temperature
Warmed up > Startup && < 2500rpm OP Low
Idle 2500rpm Dependent on thickness of oil grade (SAE 30 29-43.5 psi @ 70-80C) Moderate
As RPMs increase Increases until pressure control valve(s) open Increases
Max RPM Already previously limited by pressure control valve(s) High and dependent on ambient temperature

Most water-cooled cars have a water temperature gauge and each air-cooled vehicle should have had an oil temperature gauge as standard equipment.

Be mindful that the oil warning light only goes out when the pressure reaches 2.0 to 6.4 psi and is only a good indicator to known when the shut down the engine and without an oil temperature gauge it's harder determine why the oil pressure is low.

If you find the oil warning light stays on at idle you have a serious problem and should shut off the engine immediately and check for an oil leak. If everything checkout out you have an electrical problem or the oil pressure switch is bad and won't "open" from it's normally closed (NC) setting.

If it's flickering at idle you may be low on oil or the oil is overheating for some reason. If it flickers during highway travel, you again may have an overheating issue or your oil may simply be too thin for your climate and you should switch to a thicker grade.

If the oil is too hot and thins out too much, parts experience greater friction and wear increases. This means we need to use a viscous enough oil to keep this from happening (one that will not thin too much). As the oil breaks down and becomes contaminated from combustion by-products, it also becomes less viscous which necessitates an oil change.

Here's an example of low oil pressure due to high oil temperature at idle of all things. Note that the temperature measurements this vw owner is taking is of the case so imagine what the actual oil temperature would read (way too high!):

While temperature is important to prevent breakdown of the oil, the pressure is equally important because it governs the rate at which the fluid is flowing through the engine and cooling the moving parts.

Another risk of excessive pressure is that the oil filter will go into bypass mode and contaminants will get past it. In extrem These plugs were installed at the factory after the passages in the case were drilled.

Finding the balance between oil temperature and pressure conditions can only be discovered through test and measurement:

I've never quite understood these values because water in the crankcase won't boil off until the oil reaches 212F. The combustion of fuel produces a lot of water, some of which will blow by the piston rings:

While these temperatures above are far below the flash points of most engine oils, there are areas of the engine where the oil reaches that can get very hot (perhaps as high as 350F) which may or may not be sufficient to remove all water contamination from the crankcase.

My gut tells me that the oil temperature will reach at least 180F under load, an oil temperature of 215-220F is probably better for lubrication and will lead to less buildup of yellow pudding settling at the bottom of the oil strainer.

Assuming the oil is changed regularly and not worn out, if you stay within these ranges, you should experience minimal wear over time: lack of metals present in used oil sample (Al, Fe, Pb) which you can verify by used oil analysis.

Motor oil is the life blood of the engine and the sooner you can determine which oil is best for your climate, the longer your engine will last.



01/03/21 - Moved from OilSelection.html into separate article