F650 Oil FAQ

Edited by Winter #1935, Feb 2007
Special thanks to a trusted "consultant" who wishes to remain anonymous
Please read the Disclaimer before attempting any work in this FAQ.
Last Updated: 2 June 2007, by Winter #1935

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Oil. The blood of the modern combustion engine, plays an important role in the reduction of friction. Although oil may aid in the reduction of friction within an engine, outside of the engine it generates many heated debates. Should I use Synthetic or Mineral oil? What is the best viscosity I should be using? How often should I change my oil? Previously this FAQ contained many opinions on various topics, leaving plenty of confusion. This has been changed to provide you with factual information where possible. Experimental data is also now available, so you can see why some questions have been answered in certain ways. Where there is still debate, the arguments have been summerised into something more concise.

Please make sure you read this FAQ carefully. Please do not post messages in the forums asking "what oil should I use?". Use the information provided in this FAQ to make up your own mind over the most appropriate oil. If you have a question not answered by this FAQ, by all means ask in the forums, and you should soon have an answer.

BMW Oil Related Servce Bulletins

BMW has released several service bulletins related to oil and the F650 motorcycles. You can find more details in the Service Bulletins FAQ.

Service bulletin 2855 from 1998 covers the use of SJ engine oil in BMW motorcycles (SJ specification oil is not approved for use in BMW motorcycles).

Service bulletin 11 002 05 (015) from Feb 2005 covers the overfilling of oil in GS/Dakar/CS model bikes.

Oil Specifications Change with time
It is important to note oil specifications change over time. This can be due to many reasons, such as more modern engines requiring differing levels of additives. The main content of this FAQ was written in March 2007, so if several years have past, it may need substantial revision. However for the most part, the FAQ should remain fairly accurate.
It Really Is Simple!
Oil choice is really simple, so stop asking us "Is it okay if I use oil X, Y or Z?":
  1. Work out what ambient temperature you will be riding in (min. and max.)
  2. Using the chart below, work out a good viscosity rating.
  3. Work out if you want to use Synthetic / Semi-Synth oils based on the arguments provided in this FAQ.
  4. Go shopping. Remember SJ oils are not recommended by BMW, and do not use EC (Energy Conserving) oils.
  5. If the viscosity rating you want is not available, try something else close to your preference. You did read the section on what these ratings mean right?
If you experience problems after changing your oil, then check your choice of oil again, or change it to something else. If you are still having problems, check all the work you have done on the bike. Finally if you honestly think it is not the oil causing your problem, ask about it in the forums. The Hard Starting / Poor Running FAQ should help you. If you have any doubts about an oil, have an assay done.

General Oil Information

Oil Basics

Motor oils are required to do many things at the same time, which is why formulating oils is such a difficult task. Engine oil is expected to provide a protective film, to prevent metal to metal contact (wear) and reduce friction. It must help remove heat from engine surfaces (i.e. piston), and flush away wear particles. It also aids in sealing the piston rings, serves as a hydraulic fluid (i.e. hydraulic lifters or chain tensioners) and in some motorcycles, transfers power through a wet clutch assembly and lubricates the gearbox. In general terms, all of the above properties can be obtained to some extent using a simple basestock (and did until the mid-30's). But in mankind's never ending quest for power, engine power density continued to increase, stressing the basestock's natural lubricating abilities. Since the 30's, lubricant additives have been utilized to fortify the basestock's natural properties: by minimizing wear and deposits, reducing friction and harmful deposits, stabilizing the viscosity, and minimizing rust and corrosion.

Oil Viscosity

Viscosity is defined as the resistance to flow, and varies by temperature, pressure, and shear. To simplify, think of that bottle of pancake syrup in the refrigerator. It flows very slowly (high viscosity). Heat it up in the microwave, so you can pour it on some pancakes, and it pours easily (low viscosity). Of course, you know how scientists have to have ways to measure these kinds of things, so they invented several different ways (to keep us confused).

Saybolt Universal Seconds (SUS) is an old method, which measures the time it took (in seconds) for a measured quantity of fluid to exit through a "standard" orifice at a given temperature. The modern method uses different apparatus (automated), but is based on the same principle, and reported in metric units of centistokes (cSt), also known as mm2/sec. SUS was typically measured at 100°F and 210°F, while cSt is usually measured at 40°C and 100°C.

The term viscosity index (VI) is based on the relationship between the viscosity of the fluid at these two temperatures, and can be derived using a large table in an ASTM test method. Suffice it to say, that 100 was set as an arbitrary number; as the VI increases, the viscosity of the fluid becomes more stable as the temperature changes. A regular motor oil may have a VI of 110 - 120, a premium synthetic of 150 - 160, and a shock/fork oil of 200+. The VI is important to motor oils, as they need to have a low enough viscosity in the cold to be pumpable (to lubricate at start up), while having a high enough viscosity at operating temperature to provide a thick enough oil film to prevent metal to metal contact.

Those scientists developed a set of specifications to define the viscosity of different grades of motor oil. While it is always under revision, it is referred to as the SAE J300 viscosity specifications. Due to copyrights, it will NOT be reproduced here, but can be found at the Infineum website. I would recommend printing a copy to refer to for the rest of this discussion.

You can also find the following useful PDF about viscosity ratings.

Example SAE J300 Viscosity Specification

SAE 10W - 40

The first number (10) indicates the winter rating
The second number (40) indicates the viscosity at 100°C (212°F).

Multi-weight engine oils come with two viscosity designations. The first part is the winter, or W rating, which corresponds to conditions encountered in cold weather starting. There are two different viscosity specifications these xW oils must meet.

  1. The low temperature cranking test is to simulate the viscous drag felt by an engine attempting to "turn over" at the designated temperature. The test apparatus is a rotor-stator type, and utilizes a "quick cooling" cycle, before measuring the torque (drag) the oil creates between the small gap between the rotor and stator (again, those clever scientists have figured out a way to measure that drag, called cP, or centipoise). The lower the drag, the easier the cold weather starting, and the lower the "W" number (for comparison purposes, the viscosity roughly doubles with each 5°C drop in temperature). Note that each W grade is measure at a different temperature.
  2. The second test is called the low temperature pumping viscosity, and is designed to measure how fast the cold oil will flow toward an oil pickup in an oil pan. The reason that this is important, is that if it doesn't flow fast enough, the oil pump will suck air instead of oil (air is generally a poor lubricant). This test is sometimes called "air binding", and is to address a property found in some petroleum based oils. Normal petroleum oils (non-synthetics) contain some wax, which can crystallize into a latticework that resembles a sponge. This latticework traps the oil in the cells, and prevents flow. An additive, called a pour point depressant (PPD), can be used to disrupt formation of the latticework (wax forms needles that settle instead). Synthetics generally do not have wax to form this latticework. Again, notice that the temperature decreases with lower "W" numbers. There is also a minimum kinematic viscosity specification, but multi-grade oils should never have a problem meeting this - it typically applies to a single grade oil, 20W, for instance. So now you know what that first number (xW) in the oil's viscosity means. You probably don't think it means a lot to most motorcyclists (unless you're a cold weather die-hard), but it'll show up again later on.

The second number designates the viscosity of the oil at 100°C (212°F). This is in the ballpark for operating temperature, but most bikes can sometimes run hotter than this (250°F or more). The kinematic viscosity at 100°C defines the second number in the oil's viscosity designation, and is strictly a matter of seeing where it falls in the chart. Note that the oil also needs to meet a second viscosity specification (high-temperature high-shear - HTHS) which simulates the viscosity provided at 150°C under pressure (cams/lifters, for example).

That about covers viscosity, with the exception of noting a few things that can affect it. Fuel dilution of the oil can significantly reduce the oil's viscosity. The shear found in a bike's gearbox and clutch can shear polymers, reducing the viscosity. Normal oxidative processes tend to increase the oil's viscosity (i.e. sludge and varnish precursors). Extreme loading with dirt and soot can also increase viscosity. Unfortunately, by just measuring viscosity, you may not notice a change, as these things can combine and offset each other.

Oil and Polymer Chains

Multigrade oils are made with a basestock that will enable them to meet the W-rating...I.e. a 5W oil is made with a much lower viscosity base oil than a 10W/15W/20W or straight 40 (in that order). They then add viscosity improvers (polymers) as required to increase the warm temperature viscosity (and an additive package that includes antiwear and antioxidants). The wider the viscosity spread (or conversely, the lower the viscosity of the starting basestock), the more (not LONGER chains) of this polymer are added. A straight 40 probably has none. So the 5W50 has a LOT of polymer to get chewed up (And that 5W basestock alone doesn't make as thick of a protective oil film as a 10W or higher). The quality (viscosity index) of the starting basestock will influence how much VI improver is required (better basestock = less VII). The polymers used for VII also vary, some are more shear stable than others.

Some other things that can affect the viscosity...water/coolant content [from condensation or water pump seal leak] or fuel dilution [suggest taking samples of oil soon after taking a ride long enough to boil these off], Noack volatility of the oil [the part that gets volatilized is typically low viscosity, so the higher viscosity stuff gets left behind and artificially increases the viscosity - a cheaper and/or lower W-grade oil would be expected to show this more - making it look better - but less a concern with SL oils]. And of course, the target, shearing of the VII (operating temperature and typical operating RPM may affect this). Assuming you define lubricity as coefficient of friction, I'm guessing a 4-ball wear test would be the cheapest (although not cheap) way to go (see Amsoil's site).

Oil Specifications

Oil Links

Oil and your F650

F650 Oil Circuit

The engine used in the F650 and G650X models is based on the Rotax 654 engine. It has a dry sump, so unlike many modern bikes, the main oil tank is not located at the base of the engine. Instead, a second oil pump is used to scavange oil from the bottom of the motor, and pump it back to a remote tank. The diagram to the right shows the main oil circuit. (A wet sump motor has the crankshaft dipping into the surface of the oil in the oil pan and flinging it around, in addition to the pumped oil. If the level gets too high, the crank acts like an eggbeater and whips the oil into froth or foam (that looks almost like meringue)... which has GREATLY diminished lubricity and viscosity).

Oil System Components

Please click on the image to the right to see the oil circuit:

  1. Delivery pump
  2. Oil tank
  3. Check valve
  4. Oil filter
  5. Control valve
  6. Low-pressure line (gearbox)
  7. Low-pressure line (clutch)
  8. High-pressure line (crankshaft)
  9. High-pressure line (big end bearing)
  10. High-pressure line (camshafts)
  11. Chain tensioner
  12. Spray nozzle (for piston)
  13. Oil sump
  14. Suction pump

Note the two oil pump drive gears are plastic. To get to these two pumps, you need to completely remove the clutch.

F650 Oil Consumption

F650 Oil Change Frequency

There has long been debate over how frequently you should change your oil. The recommended frequency is every 6000miles/10000kms and at least once a year for the F650. However many people "feel" for one reason or another they should change the oil more frequently, usually 3000miles/5000kms. Thus the question is: How often should you change your oil?

Short Answer: The BMW recommended oil change interval of once every 6000miles / 10000kms is highly recommended as an oil change interval for your F650. Oil assays show a rapid change in the oil in the first 500miles after an oil change, and very slow change for the next 5500miles. In the assay analysis below, there is very little difference in the oil between 3000miles and 6000miles, so you are simply wasting money and oil.

Do not forget you should change the oil as a part of the first service at 600miles/1000kms. This is probably the most important oil change as the sump plug and oil filter will contain plenty of metal from the engine after it was manufactured.

Long Answer: In order to dertermin the most effective point to change oil, is a science - not an art. Just because you "feel" changing your oil every 3000miles/5000kms is better, does not make it better. As oil ages, its qualities change / degrade. The ability of the oil to perform its function will change. these qualities can be measured by taking a sample of oil, and measuring specific qualities - however this can only be performed in comparison to the original oil used in the engine. An oil assay the common term user in this context.

Thus we perform an experiment, where the objective is to determin the best point at which to change your oil. There are two competing theories: the first being oil should be changed more frequently than BMW specifies, and the second being the BMW specified frequency is sufficient. For the purposes of this experiment, several Chain Gang members participated, using a variety of oils.

Method: Each individual performs an oil and oil filter change as per normal. Before refilling with clean oil, a sample is taken for "base level analysis". At regular intervals (approximately 1000miles), further samples are taken for analysis. The charts below show the results of the analysis of the assays performed. Each chart has the milage associated with the oil sample on the X-axis.

Figure 1: Oil Acid Neutralizing Capacity

Figure 2: Oil Viscosity Fuel Dilution vs Milage

Figure 3: Oil Ph and Zn Levels

Figure 4: Iron Wear Metal Concentration vs. Mileage

Figure 5: Aluminium Wear Metal Concentration vs. Mileage

Analysis: Within the first 500 miles, there is a significant change in the oil. However there is very little difference between oil at 3000miles (5000kms) and 6000miles (10000kms). Thus experimental data shows changing your oil at 3000miles or 6000miles makes very limited difference. You are simply wasting oil and money.

Note: Every oil is designed for different operating conditions. For example if you are using a SAE 10W-30 oil in +30C weather, the properties of the oil are likely to degrade faster. The BMW "Maintenance Instructions" for the 2004 GS suggests: Temperatures above or below the limits quoted for the individual SAE classifications are permitted for brief periods only. In other words if you are operating outside the recommended temperatures for long / regular periods, you may want to change your oil more frequently.

Some other common arguments about oil change frequency:

Sample Oil Assay #1: Flash #412 on a Classic

So I got real tired of being confused and worried about IF I can use Castrol Syntec 5W50 full synthetic oil in my '98 F650 and decided to DO something about it. Here is what I did... I took a sample of oil from a bottle from the same lot that I put in at the oil and filter change (Sample "zero-minus"). I slightly overfilled the bike when I changed the oil. I rode it about twenty or so miles to get it fully warmed up. I removed several ounces of oil and called that "Sample Zero-Plus." I had intended to pull several samples along the way. But due to circumstance in my life, didn't. I intended to run the oil for 6000 miles, per BMW's specification. But at 6000 miles I was not very far from Mena, Arkansas. So it had more like 7,000 miles on it when I drained it. I saved a sample of that oil, too. Then, after having samples of oil sitting around in my garage from September to November, I finally got off my duff and mailed them to Lubriport for an assay. The "zero-minus" baseline-sample is free. Because I specified that I'm in a couple or three BMW clubs, I got a discount. All told, they charged me $18 to assay the oil and give me what they call "Total Base Numbers."

About the fuel dilution in the report... as far as I know, the only way fuel gets into the oil is past the rings. I replaced my rings shortly before I changed the oil at the start of this test. I figure at the next oil change/assay, I should see a lot less dilution. (Or possibly something to think REAL hard about). Also, the assayer mentioned in another email... "One of our club members had similar fuel dilution and learned that it is sometimes a result of overfilling gas tank. As fuel expands it is pushed out of tank through fuel lines and can find its way into engine, even if not running. It was in one of the BMW columns on internet someplace." Now I am not sure I am buying this. I think his club member had "pukin' petrol syndrome." In any case, my plan is to become religious about turning off my petcock when I park the bike. And more importantly, remembering to turn it back ON when I depart on the bike.

AL went from 1.7 in the sample of oil that had never seen the inside of a motor to 2.5 inside a motor after about twenty miles. Seven thousand miles later, it was 90 parts per million. The assayer noted "Moderate aluminum wear occurring." I ain't exactly thrilled about that. But... what do you propose I do about it? Should I change to a different oil? What oil? Why? Do you have any evidence that supports the fact that some other oil will reduce this moderate wear?

The viscosity dropped by about one-third in 7000 miles due to fuel contamination. I ain't gonna worry about that since the assayer doesn't have anything bad to say about it. What I will do is see if extra time on the rings AND closing the petcock makes any difference for the next oil run. If the dilution doesn't come down, THEN I will start a deeper investigation.

  1. 30% loss of viscosity.
    Caused by a 6% dilution due to fuel.
  2. Aluminum and iron floating around not captured by filter.
    These are loose molecules measured in tens of parts per million, not chunks of stuff that CAN be trapped in the filter.
  3. Boron and molybdenum 10-20% reduced.
    But not used up.

Basically, there are some things going on in my motor with which I am not thrilled. Because of the new rings and the abbreviated number of samples, I cannot de-convolve what is oil related from what is related to THIS motor. However, this study shows me that the oil holds up after 7000 miles. This study tells me that 5W50 Syntec isn't going to HURT my motor, even if I am a lazy SOB and run it WAY past 6000 miles. The oil in this study did some HARD service. 2000 of the 7000 miles was done in one weekend, on a run across Wyoming and Montana in August. 2000 of the 7000 miles was done in one weekend, on a run across Texas and Arkansas and then back across Kansas in September. 1000 of that was in a single day. At least 3000 of the 7000 miles were spent with the throttle mostly at the stop. Yes, that is not so great for a motor. Yes, I expect to see some wear associated with that sort of treatment. But what I FEARED was oil breakdown due to shear in the transmission and clutch. That CLEARLY is NOT happening. The metal stuff and dilution stuff... I believe that would be happening no matter what oil I was running.

Sample Oil Assay #2: BradG#1002 on a GS
  • I put in Golden Spectro 4, a synthetic/dino blend, $6 a liter, at the 12K service. I sampled it at +300 miles. The report shows new and this +300 mile sample.
  • For the record Golden Spectro 4: JASO MA standard as well as petroleum industry standards A.P.I SF, SG, and SH.
  • So I did a side by side with Flash's report. Things I notice are:
    1. Viscosity: GS4 20W50 starts out higher but mine dropped 20% in just 300 miles.
    2. Low metal levels BUT what is with the Magnesium, Zinc and Phosphorus levels? They must be additives in the oil because the levels in the new sample are higher than the used oil.
    3. My dilution at 300 miles is 2% on a FI bike. Not sure if carbs v. FI matters.
    The rest means little to me so I'll take Lubriport view that all is well. I'm not sure what to make of 20-30% differences when the values are in ppm. I'm thinking the real point is to spot changes from sample to sample that are significant. Just not sure I know what significant is in this case.

F650 Oil Choice

Ambiet Temperature and Oil Viscosity

SJ Oil Specification

EC Rating

Synthetic / Semi-synthetic / Mineral Oil Debate

Upper-Cylinder Lubricants and Oil Additives

Oil Brand

Oil Circuit Maintenance

Oil Pump Removal

If someone can provide images for the following, that would be fantastic. These instructions are just a guide. More detailed instructions are also required.

  1. Remove the clutch cover, clutch and clutch basket. You should see two large black plastic gears (the oil pump gears), and one large white plastic gear.
  2. On the white gear, remove the retaining ring and the thrust washer from the mainshaft. Remove the white gear.
  3. Remove the retaining ring from each of the black oil pump gears. Snap the oil pump gears out upwards. Remove the needle pins from the oil pump shafts.
  4. Remove the thrust washers. You should now be able to see the cover for the oil pumps.
  5. Remove the 6 screws from both oil pump covers. Note: These screws are listed in the BMW GS manual as using Loctite 243, and torqued to 6Nm.

Oil Pump Wear Limits

Use a set of feeler guages to check the inner and outer rotors for clearance. Note: These values are from the Rotax 655 manual.

Bleeding the Oil Circuit

You should only need to bleed the oil circuit if you have split the crankcase for maintenance. (If anyone has pictures of this process, please let us know, or post images in the Forums).

  1. Remove the oil filter (GS Oil Filter Cover or the Classic Oil Filter Cover).
  2. On the bottom right (at about the 5 o'clock position) there should be a check valve. Remove this. (Anyone have any pictures?)
  3. Remove a spark plug.
  4. Turn the engine over until oil emerges at the filter chamber.
  5. Re-install the check valve, oil filter and filter cover (but NOT the spark plug).
  6. Turn the engine over until oil comes out of the oil return line.
  7. Re-install the spark plug and run the engine for a few minutes.
  8. Check the oil level as specified in the oil change FAQ for your bike.

Misc Oil Questions

Can I get more power from a different oil?

Do some oils result in the clutch slipping?

Can I add an oil cooler to my F650?

What if I do not drive more than 6000miles/10000kms in a year?

Can I mix different oil types?

What is this white gunk under my oil cap?

Should my oil look like a mocca coffee?

My bike is overheating. Could oil be the problem?

What do I do with my "used" oil?

Can I use SK... SL... oils in my bike?

Should I soak a new oil filter before installing it?

How do I get an oil assay done?

What is it again that is aluminum and wears inside the engine?

Do additives (Zinc, Phos and Moly) make motorcycle oils more expensive?

Should I worry about fresh oil turning dark quickly?

What temperature should my oil be?

Person A: So what oil should I use?
Smartarse 1: Baby oil
Smartarse 2: Coconut oil
Smartarse 3: Massage oil, and don't forget to rotate your blinker fluid ;P
[Ed note: Do not use any of the three oils just suggested, and if you do
not know how to rotate your blinker fluid, please ask in the forums].